source: LMDZ6/branches/cirrus/libf/phylmd/ecrad/radiation/radiation_spartacus_sw.F90 @ 5435

Last change on this file since 5435 was 4853, checked in by idelkadi, 9 months ago

Ecrad update in LMDZ / Implementation of Ecrad double call in LMDZ

  • version 1.6.1 (commit 210d7911380f53a788c3cad73b3cf9b4e022ef87)
  • interface routines between lmdz and ecrad grouped in a new "lmdz" directory
  • double call method redesigned so as to go through the Ecrad initialization and configuration part only once for the entire simulation
  • clean-up in the read.F routine: delete unitules arguments
  • modification of default gas model in namelist (default: ECCKD)
File size: 78.4 KB
Line 
1! radiation_spartacus_sw.F90 - SPARTACUS shortwave solver
2!
3! (C) Copyright 2014- ECMWF.
4!
5! This software is licensed under the terms of the Apache Licence Version 2.0
6! which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
7!
8! In applying this licence, ECMWF does not waive the privileges and immunities
9! granted to it by virtue of its status as an intergovernmental organisation
10! nor does it submit to any jurisdiction.
11!
12! Author:  Robin Hogan
13! Email:   r.j.hogan@ecmwf.int
14!
15! Modifications
16!   2017-04-11  R. Hogan  Receive albedos at g-points
17!   2017-04-22  R. Hogan  Store surface fluxes at all g-points
18!   2017-06-30  R. Hogan  Reformulate to use total_albedo_direct not total_source
19!   2017-07-03  R. Hogan  Explicit calculation of encroachment
20!   2017-10-23  R. Hogan  Renamed single-character variables
21!   2018-02-20  R. Hogan  Corrected "computed" encroachment
22!   2018-03-09  R. Hogan  Security on computed encroachment, transmittance and reflectance
23!   2018-08-29  R. Hogan  Reformulate horizontal migration distances in step_migrations
24!   2018-09-02  R. Hogan  Bug fix in x_direct in step_migrations
25!   2018-09-03  R. Hogan  Security via min_cloud_effective_size
26!   2018-09-04  R. Hogan  Use encroachment_scaling and read encroachment edge_length from upper layer
27!   2018-09-13  R. Hogan  Added "Fractal" encroachment option
28!   2018-09-14  R. Hogan  Added "Zero" encroachment option
29!   2018-10-08  R. Hogan  Call calc_region_properties
30!   2018-10-15  R. Hogan  Added call to fast_expm_exchange instead of expm
31!   2019-01-12  R. Hogan  Use inv_inhom_effective_size if allocated
32!   2019-02-10  R. Hogan  Renamed "encroachment" to "entrapment"
33
34module radiation_spartacus_sw
35
36  public
37
38contains
39
40  ! Small routine for scaling cloud optical depth in the cloudy
41  ! regions
42#include "radiation_optical_depth_scaling.h"
43
44  ! This module contains just one exported subroutine, the shortwave
45  ! solver using the Speedy Algorithm for Radiative Transfer through
46  ! Cloud Sides (SPARTACUS), which can represent 3D effects using a
47  ! matrix form of the two-stream equations.
48  !
49  ! Sections:
50  !   1: Prepare general variables and arrays
51  !   2: Prepare column-specific variables and arrays
52  !   3: First loop over layers
53  !     3.1: Layer-specific initialization
54  !     3.2: Compute gamma variables
55  !       3.2a: Clear-sky case
56  !       3.2b: Cloudy case
57  !     3.3: Compute reflection, transmission and sources
58  !       3.3a: g-points with 3D effects
59  !       3.3b: g-points without 3D effects
60  !   4: Compute total albedos
61  !     4.1: Adding method
62  !     4.2: Overlap and entrapment
63  !   5: Compute fluxes
64  subroutine solver_spartacus_sw(nlev,istartcol,iendcol, &
65       &  config, single_level, thermodynamics, cloud, &
66       &  od, ssa, g, od_cloud, ssa_cloud, g_cloud, &
67       &  albedo_direct, albedo_diffuse, incoming_sw, &
68       &  flux)
69
70    use parkind1, only           : jprb
71    use yomhook,  only           : lhook, dr_hook, jphook
72
73    use radiation_io, only             : nulout
74    use radiation_config, only         : config_type, IPdfShapeGamma, &
75         &  IEntrapmentZero, IEntrapmentEdgeOnly, IEntrapmentExplicit, &
76         &  IEntrapmentExplicitNonFractal, IEntrapmentMaximum
77    use radiation_single_level, only   : single_level_type
78    use radiation_thermodynamics, only : thermodynamics_type
79    use radiation_cloud, only          : cloud_type
80    use radiation_regions, only        : calc_region_properties
81    use radiation_overlap, only        : calc_overlap_matrices
82    use radiation_flux, only           : flux_type, &
83         &                               indexed_sum, add_indexed_sum
84    use radiation_matrix
85    use radiation_two_stream, only     : calc_two_stream_gammas_sw, &
86         &  calc_reflectance_transmittance_sw, calc_frac_scattered_diffuse_sw
87    use radiation_constants, only      : Pi, GasConstantDryAir, &
88         &                               AccelDueToGravity
89
90    implicit none
91
92    ! Inputs
93    integer, intent(in) :: nlev               ! number of model levels
94    integer, intent(in) :: istartcol, iendcol ! range of columns to process
95    type(config_type),        intent(in) :: config
96    type(single_level_type),  intent(in) :: single_level
97    type(thermodynamics_type),intent(in) :: thermodynamics
98    type(cloud_type),         intent(in) :: cloud
99
100    ! Gas and aerosol optical depth, single-scattering albedo and
101    ! asymmetry factor at each shortwave g-point
102    real(jprb), intent(in), dimension(config%n_g_sw,nlev,istartcol:iendcol) :: &
103         &  od, ssa, g
104
105    ! Cloud and precipitation optical depth, single-scattering albedo and
106    ! asymmetry factor in each shortwave band
107    real(jprb), intent(in), dimension(config%n_bands_sw,nlev,istartcol:iendcol)   :: &
108         &  od_cloud, ssa_cloud, g_cloud
109
110    ! Direct and diffuse surface albedos, and the incoming shortwave
111    ! flux into a plane perpendicular to the incoming radiation at
112    ! top-of-atmosphere in each of the shortwave g points
113    real(jprb), intent(in), dimension(config%n_g_sw,istartcol:iendcol) :: &
114         &  albedo_direct, albedo_diffuse, incoming_sw
115
116    ! Output
117    type(flux_type), intent(inout):: flux
118
119    integer :: nreg, ng
120    integer :: nregactive ! =1 in clear layer, =nreg in a cloudy layer
121    integer :: jcol, jlev, jg, jreg, iband, jreg2,jreg3
122#ifdef EXPLICIT_EDGE_ENTRAPMENT
123    integer :: jreg4
124#endif
125    integer :: ng3D ! Number of g-points with small enough gas optical
126                    ! depth that 3D effects need to be represented
127
128    ! Ratio of gas constant for dry air to acceleration due to gravity
129    real(jprb), parameter :: R_over_g = GasConstantDryAir / AccelDueToGravity
130
131    real(jprb) :: mu0, one_over_mu0, tan_sza, transfer_scaling
132
133    ! The tangent of the effective zenith angle for diffuse radiation
134    ! that is appropriate for 3D transport
135    real(jprb), parameter :: tan_diffuse_angle_3d = Pi * 0.5_jprb
136
137    ! The minimum cosine of solar zenith angle to consider for 3D
138    ! effects, equivalent to one solar radius (0.2615 degrees)
139    real(jprb), parameter :: min_mu0_3d = 0.004625_jprb
140
141    ! Optical depth, single scattering albedo and asymmetry factor in
142    ! each region and (except for asymmetry) at each g-point
143    real(jprb), dimension(config%n_g_sw, config%nregions) &
144         &  :: od_region, ssa_region
145    real(jprb), dimension(config%nregions) :: g_region
146
147    ! Scattering optical depths of gases and clouds
148    real(jprb) :: scat_od, scat_od_cloud
149
150    ! The area fractions of each region
151    real(jprb) :: region_fracs(1:config%nregions,nlev,istartcol:iendcol)
152
153    ! The scaling used for the optical depth in the cloudy regions
154    real(jprb) :: od_scaling(2:config%nregions,nlev,istartcol:iendcol)
155
156    ! The length of the interface between regions jreg and jreg+1 per
157    ! unit area of gridbox, equal to L_diff^ab in Hogan and Shonk
158    ! (2013). When the first index is 3, this is the length of the
159    ! interface between regions 3 and 1. This is actually the
160    ! effective length oriented to a photon with random azimuth angle,
161    ! so is the true edge length divided by pi.
162    real(jprb) :: edge_length(3,nlev)
163
164    ! Element i,j gives the rate of 3D transfer of diffuse/direct
165    ! radiation from region i to region j, multiplied by the thickness
166    ! of the layer in m
167    real(jprb) :: transfer_rate_diffuse(config%nregions,config%nregions)
168    real(jprb) :: transfer_rate_direct(config%nregions,config%nregions)
169
170    ! Directional overlap matrices defined at all layer interfaces
171    ! including top-of-atmosphere and the surface
172    real(jprb), dimension(config%nregions,config%nregions,nlev+1, &
173         &                istartcol:iendcol) :: u_matrix, v_matrix
174
175    ! Two-stream variables
176    real(jprb), dimension(config%n_g_sw, config%nregions) &
177         &  :: gamma1, gamma2, gamma3
178
179    ! Matrix Gamma multiplied by the layer thickness z1, so units
180    ! metres.  After calling expm, this array contains the matrix
181    ! exponential of the original.
182    real(jprb) :: Gamma_z1(config%n_g_sw,3*config%nregions,3*config%nregions)
183
184    ! Diffuse reflection and transmission matrices of each layer
185    real(jprb), dimension(config%n_g_sw, config%nregions, &
186         &  config%nregions, nlev) :: reflectance, transmittance
187
188    ! Clear-sky diffuse reflection and transmission matrices of each
189    ! layer
190    real(jprb), dimension(config%n_g_sw, nlev) :: ref_clear, trans_clear
191
192    ! Matrices translating the direct flux entering the layer from
193    ! above to the reflected radiation exiting upwards (ref_dir) and
194    ! the scattered radiation exiting downwards (trans_dir_diff),
195    ! along with the direct unscattered transmission matrix
196    ! (trans_dir_dir).
197    real(jprb), dimension(config%n_g_sw, config%nregions, config%nregions, nlev) &
198         &  :: ref_dir, trans_dir_diff, trans_dir_dir
199    ! ...clear-sky equivalents
200    real(jprb), dimension(config%n_g_sw, nlev) &
201         &  :: ref_dir_clear, trans_dir_diff_clear, trans_dir_dir_clear
202
203    ! The fluxes downwelling from the bottom of the layer due to
204    ! scattering by the direct beam within the layer
205    real(jprb), dimension(config%n_g_sw, config%nregions) :: source_dn
206    ! ...clear-sky equivalent
207    real(jprb), dimension(config%n_g_sw) :: source_dn_clear
208
209    ! The fluxes upwelling just above the base of a layer due to
210    ! reflection of the direct downwelling beam; this is just used as
211    ! a temporary variable
212    real(jprb), dimension(config%n_g_sw, config%nregions) :: total_source
213
214    ! Direct downwelling flux below and above an interface between
215    ! layers into a plane perpendicular to the direction of the sun
216    real(jprb), dimension(config%n_g_sw, config%nregions) &
217         &  :: direct_dn_below, direct_dn_above
218    ! ...clear-sky equivalent (no distinction between "above/below")
219    real(jprb), dimension(config%n_g_sw) :: direct_dn_clear
220
221    ! Total albedo of the atmosphere/surface just above a layer
222    ! interface with respect to downwelling diffuse and direct
223    ! radiation at that interface, where level index = 1 corresponds
224    ! to the top-of-atmosphere
225    real(jprb), dimension(config%n_g_sw, config%nregions, &
226         &  config%nregions, nlev+1) :: total_albedo, total_albedo_direct
227    ! ...clear-sky equivalent
228    real(jprb), dimension(config%n_g_sw, nlev+1) &
229         &  :: total_albedo_clear, total_albedo_clear_direct
230
231    ! As total_albedo, but just below a layer interface
232    real(jprb), dimension(config%n_g_sw, config%nregions, config%nregions) &
233         &  :: total_albedo_below, total_albedo_below_direct
234
235    ! Temporary array for applying adding method with entrapment to
236    ! albedo matrices
237    real(jprb), dimension(config%n_g_sw, config%nregions, config%nregions) &
238         &  :: albedo_part
239
240    ! Horizontal migration distance (m) of reflected light
241    real(jprb), dimension(config%n_g_sw, config%nregions) &
242         &  :: x_diffuse, x_direct
243    ! Temporary variables when applying overlap rules
244    real(jprb), dimension(config%n_g_sw, config%nregions) &
245         &  :: x_diffuse_above, x_direct_above
246
247    real(jprb), dimension(config%n_g_sw, config%nregions, config%nregions) &
248         &  :: entrapment
249
250    ! The following is used to store matrices of the form I-A*B that
251    ! are used on the denominator of some expressions
252    real(jprb) :: denominator(config%n_g_sw,config%nregions,config%nregions)
253
254    ! Clear-sky equivalent, but actually its reciprocal to replace
255    ! some divisions by multiplications
256    real(jprb), dimension(config%n_g_sw) :: inv_denom_scalar
257
258    ! Final step in working out how much transport between regions
259    ! above occurs
260    real(jprb), dimension(config%n_g_sw) :: fractal_factor
261
262    ! Inverse of cloud effective size (m^-1)
263    real(jprb) :: inv_effective_size
264
265    ! Layer depth (m)
266    real(jprb) :: dz, layer_depth(nlev)
267
268    ! Upwelling and downwelling fluxes above/below layer interfaces
269    real(jprb), dimension(config%n_g_sw, config%nregions) &
270         &  :: flux_up_above, flux_dn_above, flux_dn_below
271    ! Clear-sky upwelling and downwelling fluxes (which don't
272    ! distinguish between whether they are above/below a layer
273    ! interface)
274    real(jprb), dimension(config%n_g_sw) :: flux_up_clear, flux_dn_clear
275
276    ! Index of top-most cloudy layer, or nlev+1 if no cloud
277    integer :: i_cloud_top
278
279    ! Keep a count of the number of calls to the two ways of computing
280    ! reflectance/transmittance matrices
281    integer :: n_calls_expm, n_calls_meador_weaver
282
283    ! Identify clear-sky layers, with pseudo layers for outer space
284    ! and below the ground, both treated as single-region clear skies
285    logical :: is_clear_sky_layer(0:nlev+1)
286
287    ! Used in computing rates of lateral radiation transfer
288    real(jprb), parameter :: four_over_pi = 4.0_jprb / Pi
289
290    ! Maximum entrapment coefficient
291    real(jprb) :: max_entr
292
293    real(jphook) :: hook_handle
294
295    if (lhook) call dr_hook('radiation_spartacus_sw:solver_spartacus_sw',0,hook_handle)
296
297    ! --------------------------------------------------------
298    ! Section 1: Prepare general variables and arrays
299    ! --------------------------------------------------------
300
301    ! Copy array dimensions to local variables for convenience
302    nreg = config%nregions
303    ng   = config%n_g_sw
304
305    ! Reset count of number of calls to the two ways to compute
306    ! reflectance/transmission matrices
307    n_calls_expm          = 0
308    n_calls_meador_weaver = 0
309
310    ! Compute the wavelength-independent region fractions and
311    ! optical-depth scalings
312    call calc_region_properties(nlev,nreg,istartcol,iendcol, &
313         &  config%i_cloud_pdf_shape == IPdfShapeGamma, &
314         &  cloud%fraction, cloud%fractional_std, region_fracs, &
315         &  od_scaling, config%cloud_fraction_threshold)
316
317    ! Compute wavelength-independent overlap matrices u_matrix and v_matrix
318    call calc_overlap_matrices(nlev,nreg,istartcol,iendcol, &
319         &  region_fracs, cloud%overlap_param, &
320         &  u_matrix, v_matrix, decorrelation_scaling=config%cloud_inhom_decorr_scaling, &
321         &  cloud_fraction_threshold=config%cloud_fraction_threshold, &
322         &  use_beta_overlap=config%use_beta_overlap, &
323         &  cloud_cover=flux%cloud_cover_sw)
324
325    if (config%iverbose >= 3) then
326      write(nulout,'(a)',advance='no') '  Processing columns'
327    end if
328
329    ! Main loop over columns
330    do jcol = istartcol, iendcol
331      ! --------------------------------------------------------
332      ! Section 2: Prepare column-specific variables and arrays
333      ! --------------------------------------------------------
334
335      if (config%iverbose >= 3) then
336        write(nulout,'(a)',advance='no') '.'
337      end if
338
339      ! Copy local cosine of the solar zenith angle
340      mu0 = single_level%cos_sza(jcol)
341
342      ! Skip profile if sun is too low in the sky
343      if (mu0 < 1.0e-10_jprb) then
344        flux%sw_dn(jcol,:) = 0.0_jprb
345        flux%sw_up(jcol,:) = 0.0_jprb
346        if (allocated(flux%sw_dn_direct)) then
347          flux%sw_dn_direct(jcol,:) = 0.0_jprb
348        end if
349        if (config%do_clear) then
350          flux%sw_dn_clear(jcol,:) = 0.0_jprb
351          flux%sw_up_clear(jcol,:) = 0.0_jprb
352          if (allocated(flux%sw_dn_direct_clear)) then
353            flux%sw_dn_direct_clear(jcol,:) = 0.0_jprb
354          end if
355        end if
356
357        if (config%do_save_spectral_flux) then
358          flux%sw_dn_band(:,jcol,:) = 0.0_jprb
359          flux%sw_up_band(:,jcol,:) = 0.0_jprb
360          if (allocated(flux%sw_dn_direct_band)) then
361            flux%sw_dn_direct_band(:,jcol,:) = 0.0_jprb
362          end if
363          if (config%do_clear) then
364            flux%sw_dn_clear_band(:,jcol,:) = 0.0_jprb
365            flux%sw_up_clear_band(:,jcol,:) = 0.0_jprb
366            if (allocated(flux%sw_dn_direct_clear_band)) then
367              flux%sw_dn_direct_clear_band(:,jcol,:) = 0.0_jprb
368            end if
369          end if
370        end if
371
372        flux%sw_dn_diffuse_surf_g(:,jcol) = 0.0_jprb
373        flux%sw_dn_direct_surf_g(:,jcol)  = 0.0_jprb
374        if (config%do_clear) then
375          flux%sw_dn_diffuse_surf_clear_g(:,jcol) = 0.0_jprb
376          flux%sw_dn_direct_surf_clear_g(:,jcol)  = 0.0_jprb
377        end if
378
379        cycle
380      end if ! sun is below the horizon
381
382      ! At this point mu0 >= 1.0e-10
383
384      ! Used to compute rate of attenuation of direct solar beam
385      ! through the atmosphere
386      one_over_mu0 = 1.0_jprb / mu0
387
388      ! The rate at which direct radiation enters cloud sides is
389      ! proportional to the tangent of the solar zenith angle, but
390      ! this gets very large when the sun is low in the sky, in which
391      ! case we limit it to one solar radius above the horizon
392      if (mu0 < min_mu0_3d) then
393        tan_sza = sqrt(1.0_jprb/(min_mu0_3d*min_mu0_3d) - 1.0_jprb)
394      else if (one_over_mu0 > 1.0_jprb) then
395        tan_sza = sqrt(one_over_mu0*one_over_mu0 - 1.0_jprb &
396             &         + config%overhead_sun_factor)
397      else
398        ! Just in case we get mu0 > 1...
399        tan_sza = sqrt(config%overhead_sun_factor)
400      end if
401
402      ! Define which layers contain cloud; assume that
403      ! cloud%crop_cloud_fraction has already been called
404      is_clear_sky_layer = .true.
405      i_cloud_top = nlev+1
406      do jlev = nlev,1,-1
407        if (cloud%fraction(jcol,jlev) > 0.0_jprb) then
408          is_clear_sky_layer(jlev) = .false.
409          i_cloud_top = jlev
410        end if
411      end do
412
413      ! --------------------------------------------------------
414      ! Section 3: First loop over layers
415      ! --------------------------------------------------------
416      ! In this section the reflectance, transmittance and sources
417      ! are computed for each layer
418      do jlev = 1,nlev ! Start at top-of-atmosphere
419        ! --------------------------------------------------------
420        ! Section 3.1: Layer-specific initialization
421        ! --------------------------------------------------------
422
423        ! Array-wise assignments
424        gamma1 = 0.0_jprb
425        gamma2 = 0.0_jprb
426        gamma3 = 0.0_jprb
427        Gamma_z1= 0.0_jprb
428        transfer_rate_direct(:,:)  = 0.0_jprb
429        transfer_rate_diffuse(:,:) = 0.0_jprb
430        edge_length(:,jlev) = 0.0_jprb
431
432        ! The following is from the hydrostatic equation
433        ! and ideal gas law: dz = dp * R * T / (p * g)
434        layer_depth(jlev) = R_over_g &
435             &  * (thermodynamics%pressure_hl(jcol,jlev+1) &
436             &     - thermodynamics%pressure_hl(jcol,jlev)) &
437             &  * (thermodynamics%temperature_hl(jcol,jlev) &
438             &     + thermodynamics%temperature_hl(jcol,jlev+1)) &
439             &  / (thermodynamics%pressure_hl(jcol,jlev) &
440             &     + thermodynamics%pressure_hl(jcol,jlev+1))
441
442        ! --------------------------------------------------------
443        ! Section 3.2: Compute gamma variables
444        ! --------------------------------------------------------
445        if (is_clear_sky_layer(jlev)) then
446          ! --- Section 3.2a: Clear-sky case --------------------
447
448          nregactive = 1   ! Only region 1 (clear-sky) is active
449
450          ! Copy optical depth and single-scattering albedo of
451          ! clear-sky region
452          od_region(1:ng,1) = od(1:ng,jlev,jcol)
453          ssa_region(1:ng,1) = ssa(1:ng,jlev,jcol)
454
455          ! Compute two-stream variables gamma1-gamma3 (gamma4=1-gamma3)
456          call calc_two_stream_gammas_sw(ng, &
457               &  mu0, ssa(1:ng,jlev,jcol), g(1:ng,jlev,jcol), &
458               &  gamma1(1:ng,1), gamma2(1:ng,1), gamma3(1:ng,1))
459
460          if (config%use_expm_everywhere) then
461            ! Treat cloud-free layer as 3D: the matrix exponential
462            ! "expm" is used as much as possible (provided the
463            ! optical depth is not too high). ng3D is initially
464            ! set to the total number of g-points, then the
465            ! clear-sky optical depths are searched until a value
466            ! exceeds the threshold for treating 3D effects, and
467            ! if found it is reset to that.  Note that we are
468            ! assuming that the g-points have been reordered in
469            ! approximate order of gas optical depth.
470            ng3D = ng
471            do jg = 1, ng
472              if (od_region(jg,1) > config%max_gas_od_3D) then
473                ng3D = jg-1
474                exit
475              end if
476            end do
477          else
478            ! Otherwise treat cloud-free layer using the classical
479            ! Meador & Weaver formulae for all g-points
480            ng3D = 0
481          end if
482
483
484        else
485          ! --- Section 3.2b: Cloudy case -----------------------
486
487          ! Default number of g-points to treat with
488          ! matrix-exponential scheme
489          if (config%use_expm_everywhere) then
490            ng3D = ng   ! All g-points
491          else
492            ng3D = 0    ! No g-points
493          end if
494
495          if (config%do_3d_effects .and. &
496               &  allocated(cloud%inv_cloud_effective_size) .and. &
497               &  .not. (nreg == 2 .and. cloud%fraction(jcol,jlev) &
498               &  > 1.0-config%cloud_fraction_threshold)) then
499            if (cloud%inv_cloud_effective_size(jcol,jlev) > 0.0_jprb) then
500              ! 3D effects are only simulated if
501              ! inv_cloud_effective_size is defined and greater
502              ! than zero
503              ng3D = ng
504
505              ! Depth of current layer
506              dz = layer_depth(jlev)
507
508              ! Compute cloud edge length per unit area of gridbox
509              ! from rearranging Hogan & Shonk (2013) Eq. 45, but
510              ! adding a factor of (1-frac) so that a region that
511              ! fully occupies the gridbox (frac=1) has an edge of
512              ! zero. We can therefore use the fraction of clear sky,
513              ! region_fracs(1,jlev,jcol) for convenience instead. The
514              ! pi on the denominator means that this is actually edge
515              ! length with respect to a light ray with a random
516              ! azimuthal direction.
517              edge_length(1,jlev) = four_over_pi &
518                   &  * region_fracs(1,jlev,jcol)*(1.0_jprb-region_fracs(1,jlev,jcol)) &
519                   &  * min(cloud%inv_cloud_effective_size(jcol,jlev), &
520                   &        1.0_jprb / config%min_cloud_effective_size)
521              if (nreg > 2) then
522                ! The corresponding edge length between the two cloudy
523                ! regions is computed in the same way but treating the
524                ! optically denser of the two regions (region 3) as
525                ! the cloud; note that the fraction of this region may
526                ! be less than that of the optically less dense of the
527                ! two regions (region 2).  For increased flexibility,
528                ! the user may specify the effective size of
529                ! inhomogeneities separately from the cloud effective
530                ! size.
531                if (allocated(cloud%inv_inhom_effective_size)) then
532                  edge_length(2,jlev) = four_over_pi &
533                       &  * region_fracs(3,jlev,jcol)*(1.0_jprb-region_fracs(3,jlev,jcol)) &
534                       &  * min(cloud%inv_inhom_effective_size(jcol,jlev), &
535                       &        1.0_jprb / config%min_cloud_effective_size)
536                else
537                  edge_length(2,jlev) = four_over_pi &
538                       &  * region_fracs(3,jlev,jcol)*(1.0_jprb-region_fracs(3,jlev,jcol)) &
539                       &  * min(cloud%inv_cloud_effective_size(jcol,jlev), &
540                       &        1.0_jprb / config%min_cloud_effective_size)
541                end if
542
543                ! In the case of three regions, some of the cloud
544                ! boundary may go directly to the "thick" region
545                if (config%clear_to_thick_fraction > 0.0_jprb) then
546                  edge_length(3,jlev) = config%clear_to_thick_fraction &
547                       &  * min(edge_length(1,jlev), edge_length(2,jlev))
548                  edge_length(1,jlev) = edge_length(1,jlev) - edge_length(3,jlev)
549                  edge_length(2,jlev) = edge_length(2,jlev) - edge_length(3,jlev)
550                else
551                  edge_length(3,jlev) = 0.0_jprb
552                end if
553              end if
554
555              do jreg = 1, nreg-1
556                ! Compute lateral transfer rates from region jreg to
557                ! jreg+1 following Hogan & Shonk (2013) Eq. 47, but
558                ! multiplied by dz because the transfer rate is
559                ! vertically integrated across the depth of the layer
560                if (region_fracs(jreg,jlev,jcol) > epsilon(1.0_jprb)) then
561                  transfer_rate_direct(jreg,jreg+1) = dz &
562                       &  * edge_length(jreg,jlev) * tan_sza / region_fracs(jreg,jlev,jcol)
563                  transfer_rate_diffuse(jreg,jreg+1) = dz &
564                       &  * edge_length(jreg,jlev) &
565                       &  * tan_diffuse_angle_3d / region_fracs(jreg,jlev,jcol)
566                end if
567                ! Compute transfer rates from region jreg+1 to
568                ! jreg
569                if (region_fracs(jreg+1,jlev,jcol) > epsilon(1.0_jprb)) then
570                  transfer_rate_direct(jreg+1,jreg) = dz &
571                       &  * edge_length(jreg,jlev) &
572                       &  * tan_sza / region_fracs(jreg+1,jlev,jcol)
573                  transfer_rate_diffuse(jreg+1,jreg) = dz &
574                       &  * edge_length(jreg,jlev) &
575                       &  * tan_diffuse_angle_3d / region_fracs(jreg+1,jlev,jcol)
576                end if
577              end do
578
579              ! Compute transfer rates directly between regions 1 and
580              ! 3
581              if (edge_length(3,jlev) > 0.0_jprb) then
582                if (region_fracs(1,jlev,jcol) > epsilon(1.0_jprb)) then
583                  transfer_rate_direct(1,3) = dz &
584                       &  * edge_length(3,jlev) * tan_sza / region_fracs(1,jlev,jcol)
585                  transfer_rate_diffuse(1,3) = dz &
586                       &  * edge_length(3,jlev) &
587                       &  * tan_diffuse_angle_3d / region_fracs(1,jlev,jcol)
588                end if
589                if (region_fracs(3,jlev,jcol) > epsilon(1.0_jprb)) then
590                  transfer_rate_direct(3,1) = dz &
591                       &  * edge_length(3,jlev) * tan_sza / region_fracs(3,jlev,jcol)
592                  transfer_rate_diffuse(3,1) = dz &
593                       &  * edge_length(3,jlev) &
594                       &  * tan_diffuse_angle_3d / region_fracs(3,jlev,jcol)
595                end if
596              end if
597
598              ! Don't allow the transfer rate out of a region to be
599              ! equivalent to a loss of exp(-10) through the layer
600              where (transfer_rate_direct > config%max_3d_transfer_rate)
601                transfer_rate_direct = config%max_3d_transfer_rate
602              end where
603              where (transfer_rate_diffuse > config%max_3d_transfer_rate)
604                transfer_rate_diffuse = config%max_3d_transfer_rate
605              end where
606
607            end if ! Cloud has edge length required for 3D effects
608          end if ! Include 3D effects
609
610          ! In a cloudy layer the number of active regions equals
611          ! the number of regions
612          nregactive = nreg
613
614          ! Compute scattering properties of the regions at each
615          ! g-point, mapping from the cloud properties
616          ! defined in each band.
617          do jg = 1,ng
618            ! Mapping from g-point to band
619            iband = config%i_band_from_reordered_g_sw(jg)
620
621            ! Scattering optical depth of clear-sky region
622            scat_od = od(jg,jlev,jcol)*ssa(jg,jlev,jcol)
623
624            ! Scattering properties of clear-sky regions copied
625            ! over
626            od_region(jg,1)  = od(jg, jlev, jcol)
627            ssa_region(jg,1) = ssa(jg, jlev, jcol)
628            g_region(1)      = g(jg, jlev, jcol)
629
630            ! Loop over cloudy regions
631            do jreg = 2,nreg
632              scat_od_cloud = od_cloud(iband,jlev,jcol) &
633                   &  * ssa_cloud(iband,jlev,jcol)*od_scaling(jreg,jlev,jcol)
634              ! Add scaled cloud optical depth to clear-sky value
635              od_region(jg,jreg) = od(jg,jlev,jcol) &
636                   &  + od_cloud(iband,jlev,jcol)*od_scaling(jreg,jlev,jcol)
637              ! Compute single-scattering albedo and asymmetry
638              ! factor of gas-cloud combination
639              ssa_region(jg,jreg) = (scat_od+scat_od_cloud) &
640                   &  / od_region(jg,jreg)
641              g_region(jreg) = (scat_od*g(jg,jlev,jcol) &
642                   &  + scat_od_cloud * g_cloud(iband,jlev,jcol)) &
643                   &  / (scat_od + scat_od_cloud)
644
645              ! Apply maximum cloud optical depth for stability in the
646              ! 3D case
647              if (od_region(jg,jreg) > config%max_cloud_od) then
648                od_region(jg,jreg) = config%max_cloud_od
649              end if
650
651            end do
652
653            ! Calculate two-stream variables gamma1-gamma3 of all
654            ! regions at once
655            call calc_two_stream_gammas_sw(nreg, &
656                 &  mu0, ssa_region(jg,:), g_region, &
657                 &  gamma1(jg,:), gamma2(jg,:), gamma3(jg,:))
658
659            ! Loop is in order of g-points with typically
660            ! increasing optical depth: if optical depth of
661            ! clear-sky region exceeds a threshold then turn off
662            ! 3D effects for any further g-points
663            if (ng3D == ng &
664                 &  .and. od_region(jg,1) > config%max_gas_od_3D) then
665              ng3D = jg-1
666            end if
667          end do ! Loop over g points
668        end if ! Cloudy level
669
670        ! --------------------------------------------------------
671        ! Section 3.3: Compute reflection, transmission and emission
672        ! --------------------------------------------------------
673        if (ng3D > 0) then
674          ! --- Section 3.3a: g-points with 3D effects ----------
675
676          ! 3D effects need to be represented in "ng3D" of the g
677          ! points.  This is done by creating ng3D square matrices
678          ! each of dimension 3*nreg by 3*nreg, computing the matrix
679          ! exponential, then computing the various
680          ! transmission/reflectance matrices from that.
681          do jreg = 1,nregactive
682            ! Write the diagonal elements of -Gamma1*z1
683            Gamma_z1(1:ng3D,jreg,jreg) &
684                 &  = od_region(1:ng3D,jreg)*gamma1(1:ng3D,jreg)
685            ! Write the diagonal elements of +Gamma2*z1
686            Gamma_z1(1:ng3D,jreg+nreg,jreg) &
687                 &  = od_region(1:ng3D,jreg)*gamma2(1:ng3D,jreg)
688            ! Write the diagonal elements of -Gamma3*z1
689            Gamma_z1(1:ng3D,jreg,jreg+2*nreg) &
690                 &  = -od_region(1:ng3D,jreg)*ssa_region(1:ng3D,jreg) &
691                 &  * gamma3(1:ng3D,jreg)
692
693            ! Write the diagonal elements of +Gamma4*z1
694            Gamma_z1(1:ng3D,jreg+nreg,jreg+2*nreg) &
695                 &  = od_region(1:ng3D,jreg)*ssa_region(1:ng3D,jreg) &
696                 &  * (1.0_jprb - gamma3(1:ng3D,jreg))
697
698            ! Write the diagonal elements of +Gamma0*z1
699            Gamma_z1(1:ng3D,jreg+2*nreg,jreg+2*nreg) &
700                 &  = -od_region(1:ng3D,jreg)*one_over_mu0
701          end do
702
703          do jreg = 1,nregactive-1
704            ! Write the elements of -Gamma1*z1 concerned with 3D
705            ! transport
706            Gamma_z1(1:ng3D,jreg,jreg) = Gamma_z1(1:ng3D,jreg,jreg) &
707                 &  + transfer_rate_diffuse(jreg,jreg+1)
708            Gamma_z1(1:ng3D,jreg+1,jreg+1) = Gamma_z1(1:ng3D,jreg+1,jreg+1) &
709                 &  + transfer_rate_diffuse(jreg+1,jreg)
710            Gamma_z1(1:ng3D,jreg+1,jreg) = -transfer_rate_diffuse(jreg,jreg+1)
711            Gamma_z1(1:ng3D,jreg,jreg+1) = -transfer_rate_diffuse(jreg+1,jreg)
712            ! Write the elements of +Gamma0*z1 concerned with 3D
713            ! transport
714            Gamma_z1(1:ng3D,jreg+2*nreg,jreg+2*nreg) &
715                 &  = Gamma_z1(1:ng3D,jreg+2*nreg,jreg+2*nreg) &
716                 &  - transfer_rate_direct(jreg,jreg+1)
717            Gamma_z1(1:ng3D,jreg+2*nreg+1,jreg+2*nreg+1) &
718                 &  = Gamma_z1(1:ng3D,jreg+2*nreg+1,jreg+2*nreg+1) &
719                 &  - transfer_rate_direct(jreg+1,jreg)
720            Gamma_z1(1:ng3D,jreg+2*nreg+1,jreg+2*nreg) &
721                 &  = transfer_rate_direct(jreg,jreg+1)
722            Gamma_z1(1:ng3D,jreg+2*nreg,jreg+2*nreg+1) &
723                 &  = transfer_rate_direct(jreg+1,jreg)
724          end do
725
726          ! Possible flow between regions a and c
727          if (edge_length(3,jlev) > 0.0_jprb) then
728            ! Diffuse transport
729            Gamma_z1(1:ng3D,1,1) = Gamma_z1(1:ng3D,1,1) &
730                 &  + transfer_rate_diffuse(1,3)
731            Gamma_z1(1:ng3D,3,3) = Gamma_z1(1:ng3D,3,3) &
732                 &  + transfer_rate_diffuse(3,1)
733            Gamma_z1(1:ng3D,3,1) = -transfer_rate_diffuse(1,3)
734            Gamma_z1(1:ng3D,1,3) = -transfer_rate_diffuse(3,1)
735            ! Direct transport
736            Gamma_z1(1:ng3D,1+2*nreg,1+2*nreg) = Gamma_z1(1:ng3D,1+2*nreg,1+2*nreg) &
737                 &  - transfer_rate_direct(1,3)
738            Gamma_z1(1:ng3D,3+2*nreg,3+2*nreg) = Gamma_z1(1:ng3D,3+2*nreg,3+2*nreg) &
739                 &  - transfer_rate_direct(3,1)
740            Gamma_z1(1:ng3D,3+2*nreg,1+2*nreg) = transfer_rate_direct(1,3)
741            Gamma_z1(1:ng3D,1+2*nreg,3+2*nreg) = transfer_rate_direct(3,1)
742          end if
743
744          ! Copy Gamma1*z1
745          Gamma_z1(1:ng3D,nreg+1:nreg+nregactive,nreg+1:nreg+nregactive) &
746               &  = -Gamma_z1(1:ng3D,1:nregactive,1:nregactive)
747          ! Copy Gamma2*z1
748          Gamma_z1(1:ng3D,1:nregactive,nreg+1:nreg+nregactive) &
749               &  = -Gamma_z1(1:ng3D,nreg+1:nreg+nregactive,1:nregactive)
750
751          ! Compute the matrix exponential of Gamma_z1, returning the
752          ! result in-place
753          call expm(ng, ng3D, 3*nreg, Gamma_z1, IMatrixPatternShortwave)
754
755          ! Update count of expm calls
756          n_calls_expm = n_calls_expm + ng3D
757
758          ! Direct transmission matrix
759          trans_dir_dir(1:ng3D,:,:,jlev) = min(1.0_jprb,max(0.0_jprb, &
760               &  Gamma_z1(1:ng3D,2*nreg+1:3*nreg, 2*nreg+1:3*nreg)))
761          ! Diffuse reflectance matrix; security on negative values
762          ! necessary occasionally for very low cloud fraction and very high
763          ! in-cloud optical depth
764          reflectance(1:ng3D,:,:,jlev) = min(1.0_jprb,max(0.0_jprb, &
765               &  -solve_mat(ng,ng3D,nreg,Gamma_z1(1:ng3D,1:nreg,1:nreg), &
766               &             Gamma_z1(1:ng3D,1:nreg,nreg+1:2*nreg))))
767          ! Diffuse transmission matrix
768          transmittance(1:ng3D,:,:,jlev) = min(1.0_jprb,max(0.0_jprb, &
769               &  mat_x_mat(ng,ng3D,nreg,Gamma_z1(1:ng3D,nreg+1:2*nreg,1:nreg), &
770               &            reflectance(1:ng3D,:,:,jlev)) &
771               &  + Gamma_z1(1:ng3D,nreg+1:2*nreg,nreg+1:2*nreg)))
772          ! Transfer matrix between downward direct and upward
773          ! diffuse
774          ref_dir(1:ng3D,:,:,jlev) = min(mu0,max(0.0_jprb, &
775               &  -solve_mat(ng,ng3D,nreg,Gamma_z1(1:ng3D,1:nreg,1:nreg), &
776               &             Gamma_z1(1:ng3D,1:nreg,2*nreg+1:3*nreg))))
777          ! Transfer matrix between downward direct and downward
778          ! diffuse in layer interface below.  Include correction for
779          ! trans_dir_diff out of plausible bounds (note that Meador &
780          ! Weaver has the same correction in radiation_two_stream.F90
781          ! - this is not just an expm thing)
782          trans_dir_diff(1:ng3D,:,:,jlev) = min(mu0,max(0.0_jprb, &
783               &  mat_x_mat(ng,ng3D,nreg,Gamma_z1(1:ng3D,nreg+1:2*nreg,1:nreg), &
784               &            ref_dir(1:ng3D,:,:,jlev)) &
785               &  + Gamma_z1(1:ng3D,nreg+1:2*nreg,2*nreg+1:3*nreg)))
786
787        end if ! we are treating 3D effects for some g points
788
789        ! --- Section 3.3b: g-points without 3D effects ----------
790
791        ! Compute reflectance, transmittance and associated terms for
792        ! clear skies, using the Meador-Weaver formulas
793        call calc_reflectance_transmittance_sw(ng, &
794             &  mu0, od_region(1:ng,1), ssa_region(1:ng,1), &
795             &  gamma1(1:ng,1), gamma2(1:ng,1), gamma3(1:ng,1), &
796             &  ref_clear(1:ng,jlev), trans_clear(1:ng,jlev), &
797             &  ref_dir_clear(1:ng,jlev), trans_dir_diff_clear(1:ng,jlev), &
798             &  trans_dir_dir_clear(1:ng,jlev) )
799
800        n_calls_meador_weaver = n_calls_meador_weaver + ng
801
802        if (ng3D < ng) then
803          ! Some of the g points are to be treated using the
804          ! conventional plane-parallel method.  First zero the
805          ! relevant parts of the matrices
806          trans_dir_dir (ng3D+1:ng,:,:,jlev) = 0.0_jprb
807          reflectance   (ng3D+1:ng,:,:,jlev) = 0.0_jprb
808          transmittance (ng3D+1:ng,:,:,jlev) = 0.0_jprb
809          ref_dir       (ng3D+1:ng,:,:,jlev) = 0.0_jprb
810          trans_dir_diff(ng3D+1:ng,:,:,jlev) = 0.0_jprb
811
812          ! Since there is no lateral transport, the clear-sky parts
813          ! of the arrays can be copied from the clear-sky arrays
814          trans_dir_dir (ng3D+1:ng,1,1,jlev) = trans_dir_dir_clear (ng3D+1:ng,jlev)
815          reflectance   (ng3D+1:ng,1,1,jlev) = ref_clear           (ng3D+1:ng,jlev)
816          transmittance (ng3D+1:ng,1,1,jlev) = trans_clear         (ng3D+1:ng,jlev)
817          ref_dir       (ng3D+1:ng,1,1,jlev) = ref_dir_clear       (ng3D+1:ng,jlev)
818          trans_dir_diff(ng3D+1:ng,1,1,jlev) = trans_dir_diff_clear(ng3D+1:ng,jlev)
819
820          ! Compute reflectance, transmittance and associated terms
821          ! for each cloudy region, using the Meador-Weaver formulas
822          do jreg = 2, nregactive
823            call calc_reflectance_transmittance_sw(ng-ng3D, &
824                 &  mu0, &
825                 &  od_region(ng3D+1:ng,jreg), ssa_region(ng3D+1:ng,jreg), &
826                 &  gamma1(ng3D+1:ng,jreg), gamma2(ng3D+1:ng,jreg), &
827                 &  gamma3(ng3D+1:ng,jreg), &
828                 &  reflectance(ng3D+1:ng,jreg,jreg,jlev), &
829                 &  transmittance(ng3D+1:ng,jreg,jreg,jlev), &
830                 &  ref_dir(ng3D+1:ng,jreg,jreg,jlev), &
831                 &  trans_dir_diff(ng3D+1:ng,jreg,jreg,jlev), &
832                 &  trans_dir_dir(ng3D+1:ng,jreg,jreg,jlev) )
833          end do
834          n_calls_meador_weaver &
835               &  = n_calls_meador_weaver + (ng-ng3D)*(nregactive-1)
836        end if
837
838      end do ! Loop over levels
839
840      ! --------------------------------------------------------
841      ! Section 4: Compute total albedos
842      ! --------------------------------------------------------
843
844      total_albedo(:,:,:,:)        = 0.0_jprb
845      total_albedo_direct(:,:,:,:) = 0.0_jprb
846
847      if (config%do_clear) then
848        total_albedo_clear(:,:)        = 0.0_jprb
849        total_albedo_clear_direct(:,:) = 0.0_jprb
850      end if
851
852      ! Calculate the upwelling radiation scattered from the direct
853      ! beam incident on the surface, and copy the surface albedo
854      ! into total_albedo
855      do jreg = 1,nreg
856        do jg = 1,ng
857          total_albedo(jg,jreg,jreg,nlev+1) = albedo_diffuse(jg,jcol)
858          total_albedo_direct(jg,jreg,jreg,nlev+1) &
859               &  = mu0 * albedo_direct(jg,jcol)
860        end do
861      end do
862
863      if (config%do_clear) then
864        ! Surface albedo is the same
865        total_albedo_clear(1:ng,nlev+1) = total_albedo(1:ng,1,1,nlev+1)
866        total_albedo_clear_direct(1:ng,nlev+1) &
867             &  = total_albedo_direct(1:ng,1,1,nlev+1)
868      end if
869
870      ! Horizontal migration distances of reflected radiation at the
871      ! surface are zero
872      x_diffuse = 0.0_jprb
873      x_direct  = 0.0_jprb
874
875      ! Work back up through the atmosphere computing the total albedo
876      ! of the atmosphere below that point using the adding method
877      do jlev = nlev,1,-1
878
879        ! --------------------------------------------------------
880        ! Section 4.1: Adding method
881        ! --------------------------------------------------------
882
883        if (config%do_clear) then
884          ! Use adding method for clear-sky arrays; note that there
885          ! is no need to consider "above" and "below" quantities
886          ! since with no cloud overlap to worry about, these are
887          ! the same
888          inv_denom_scalar(:) = 1.0_jprb &
889               &  / (1.0_jprb - total_albedo_clear(:,jlev+1)*ref_clear(:,jlev))
890          total_albedo_clear(:,jlev) = ref_clear(:,jlev) &
891               &  + trans_clear(:,jlev)*trans_clear(:,jlev)*total_albedo_clear(:,jlev+1) &
892               &  * inv_denom_scalar(:)
893          total_albedo_clear_direct(:,jlev) = ref_dir_clear(:,jlev) &
894               &  + (trans_dir_dir_clear(:,jlev) * total_albedo_clear_direct(:,jlev+1) &
895               &    +trans_dir_diff_clear(:,jlev) * total_albedo_clear(:,jlev+1)) &
896               &  * trans_clear(:,jlev) * inv_denom_scalar(:)
897        end if
898
899        if (is_clear_sky_layer(jlev)) then
900          ! Clear-sky layer: use scalar adding method
901          inv_denom_scalar(:) = 1.0_jprb &
902               &  / (1.0_jprb - total_albedo(:,1,1,jlev+1)*reflectance(:,1,1,jlev))
903          total_albedo_below = 0.0_jprb
904          total_albedo_below(:,1,1) = reflectance(:,1,1,jlev) &
905               &  + transmittance(:,1,1,jlev)  * transmittance(:,1,1,jlev) &
906               &  * total_albedo(:,1,1,jlev+1) * inv_denom_scalar(:)
907          total_albedo_below_direct = 0.0_jprb
908          total_albedo_below_direct(:,1,1) = ref_dir(:,1,1,jlev) &
909               &  + (trans_dir_dir(:,1,1,jlev)*total_albedo_direct(:,1,1,jlev+1) &
910               &    +trans_dir_diff(:,1,1,jlev)*total_albedo(:,1,1,jlev+1)) &
911               &  * transmittance(:,1,1,jlev) * inv_denom_scalar(:)
912        else
913          ! Cloudy layer: use matrix adding method
914          denominator = identity_minus_mat_x_mat(ng,ng,nreg, &
915               &  total_albedo(:,:,:,jlev+1), reflectance(:,:,:,jlev))
916          total_albedo_below = reflectance(:,:,:,jlev) &
917               &  + mat_x_mat(ng,ng,nreg,transmittance(:,:,:,jlev), &
918               &  solve_mat(ng,ng,nreg,denominator, &
919               &  mat_x_mat(ng,ng,nreg,total_albedo(:,:,:,jlev+1), &
920               &  transmittance(:,:,:,jlev))))
921          total_albedo_below_direct = ref_dir(:,:,:,jlev) &
922               &  + mat_x_mat(ng,ng,nreg,transmittance(:,:,:,jlev), &
923               &  solve_mat(ng,ng,nreg,denominator, &
924               &    mat_x_mat(ng,ng,nreg,total_albedo_direct(:,:,:,jlev+1), &
925               &                       trans_dir_dir(:,:,:,jlev)) &
926               &   +mat_x_mat(ng,ng,nreg,total_albedo(:,:,:,jlev+1), &
927               &                       trans_dir_diff(:,:,:,jlev))))
928        end if
929
930        ! --------------------------------------------------------
931        ! Section 4.2: Overlap and entrapment
932        ! --------------------------------------------------------
933
934#ifndef PRINT_ENTRAPMENT_DATA
935        if ((config%i_3d_sw_entrapment == IEntrapmentExplicitNonFractal &
936             &  .or. config%i_3d_sw_entrapment == IEntrapmentExplicit) &
937             &  .and. jlev >= i_cloud_top) then
938#else
939        if (config%i_3d_sw_entrapment == IEntrapmentExplicitNonFractal &
940             &  .or. config%i_3d_sw_entrapment == IEntrapmentExplicit) then
941#endif
942          !  "Explicit entrapment": we have the horizontal migration
943          !  distances just above the base of the layer, and need to
944          !  step them to just below the top of the same layer
945          call step_migrations(ng, nreg, cloud%fraction(jcol,jlev), &
946               & layer_depth(jlev), tan_diffuse_angle_3d, tan_sza, &
947               &  reflectance(:,:,:,jlev), transmittance(:,:,:,jlev), &
948               &  ref_dir(:,:,:,jlev), trans_dir_dir(:,:,:,jlev), &
949               &  trans_dir_diff(:,:,:,jlev), total_albedo(:,:,:,jlev+1), &
950               &  total_albedo_direct(:,:,:,jlev+1), &
951               &  x_diffuse, x_direct)
952
953#ifdef PRINT_ENTRAPMENT_DATA
954          ! Write out for later analysis: these are the entrapment
955          ! statistics at the top of layer "jlev"
956          ! Note that number of scattering events is now not computed,
957          ! so print "1.0"
958          if (nreg == 2) then
959            write(101,'(i4,i4,6e14.6)') jcol, jlev, &
960                 &  x_direct(1,:), x_diffuse(1,:), x_direct(1,:)*0.0_jprb+1.0_jprb
961          else
962            write(101,'(i4,i4,9e14.6)') jcol, jlev, &
963                 &  x_direct(1,1:3), x_diffuse(1,1:3), 1.0_jprb,1.0_jprb,1.0_jprb
964          end if
965#endif
966
967        end if
968
969        ! Account for cloud overlap when converting albedo and source
970        ! below a layer interface to the equivalent values just above
971        if (is_clear_sky_layer(jlev) .and. is_clear_sky_layer(jlev-1)) then
972          ! If both layers are cloud free, this is trivial...
973          total_albedo(:,:,:,jlev) = 0.0_jprb
974          total_albedo(:,1,1,jlev) = total_albedo_below(:,1,1)
975          total_albedo_direct(:,:,:,jlev) = 0.0_jprb
976          total_albedo_direct(:,1,1,jlev) = total_albedo_below_direct(:,1,1)
977
978        else if (config%i_3d_sw_entrapment == IEntrapmentMaximum &
979             &  .or. is_clear_sky_layer(jlev-1)) then
980          ! "Maximum entrapment": use the overlap matrices u_matrix and v_matrix
981          ! (this is the original SPARTACUS method)
982          total_albedo(:,:,:,jlev) = singlemat_x_mat(ng,ng,nreg,&
983               &  u_matrix(:,:,jlev,jcol), &
984               &  mat_x_singlemat(ng,ng,nreg,total_albedo_below,&
985               &  v_matrix(:,:,jlev,jcol)))
986          total_albedo_direct(:,:,:,jlev) = singlemat_x_mat(ng,ng,nreg,&
987               &  u_matrix(:,:,jlev,jcol), &
988               &  mat_x_singlemat(ng,ng,nreg,total_albedo_below_direct,&
989               &  v_matrix(:,:,jlev,jcol)))
990
991        else if (config%i_3d_sw_entrapment == IEntrapmentZero) then
992          ! "Zero entrapment": even radiation transported
993          ! laterally between regions in the layers below is
994          ! reflected back up into the same region. First diffuse
995          ! radiation:
996          total_albedo(:,:,:,jlev) = 0.0_jprb
997          do jreg = 1,nreg    ! Target layer (jlev-1)
998            do jreg2 = 1,nreg ! Current layer (jlev)
999              total_albedo(:,jreg,jreg,jlev) = total_albedo(:,jreg,jreg,jlev) &
1000                   &  + sum(total_albedo_below(:,:,jreg2),2) &
1001                   &  * v_matrix(jreg2,jreg,jlev,jcol)
1002            end do
1003          end do
1004          ! ...then direct radiation:
1005          total_albedo_direct(:,:,:,jlev) = 0.0_jprb
1006          do jreg = 1,nreg    ! Target layer (jlev-1)
1007            do jreg2 = 1,nreg ! Current layer (jlev)
1008              total_albedo_direct(:,jreg,jreg,jlev) = total_albedo_direct(:,jreg,jreg,jlev) &
1009                   &  + sum(total_albedo_below_direct(:,:,jreg2),2) &
1010                   &  * v_matrix(jreg2,jreg,jlev,jcol)
1011            end do
1012          end do
1013
1014        else
1015          ! Controlled entrapment
1016
1017#ifdef EXPLICIT_EDGE_ENTRAPMENT
1018          ! If "EXPLICIT_EDGE_ENTRAPMENT" is defined then we use the
1019          ! explicit entrapment approach for both horizontal transport
1020          ! within regions, and horizontal transport between regions
1021          ! (otherwise, horizontal transport between regions is
1022          ! automatically treated using maximum entrapment). This is
1023          ! experimental, which is why it is not a run-time option.
1024
1025          if (config%i_3d_sw_entrapment == IEntrapmentEdgeOnly) then
1026#endif
1027          ! Add the contribution from off-diagonal elements of the
1028          ! albedo matrix in the lower layer, i.e. radiation that
1029          ! flows between regions...
1030
1031          ! First diffuse radiation:
1032          albedo_part = total_albedo_below
1033          do jreg = 1,nreg
1034            albedo_part(:,jreg,jreg) = 0.0_jprb
1035          end do
1036          total_albedo(:,:,:,jlev) = singlemat_x_mat(ng,ng,nreg,&
1037               &  u_matrix(:,:,jlev,jcol), &
1038               &  mat_x_singlemat(ng,ng,nreg,albedo_part,&
1039               &  v_matrix(:,:,jlev,jcol)))
1040          ! ...then direct radiation:
1041          albedo_part = total_albedo_below_direct
1042          do jreg = 1,nreg
1043            albedo_part(:,jreg,jreg) = 0.0_jprb
1044          end do
1045          total_albedo_direct(:,:,:,jlev) = singlemat_x_mat(ng,ng,nreg,&
1046               &  u_matrix(:,:,jlev,jcol), &
1047               &  mat_x_singlemat(ng,ng,nreg,albedo_part,&
1048               &  v_matrix(:,:,jlev,jcol)))
1049
1050#ifdef EXPLICIT_EDGE_ENTRAPMENT
1051end if
1052#endif
1053         
1054          ! Now the contribution from the diagonals of the albedo
1055          ! matrix in the lower layer
1056          if (config%i_3d_sw_entrapment == IEntrapmentEdgeOnly &
1057               &  .or. (.not. config%do_3d_effects)) then
1058            ! "Edge-only entrapment": the operation we perform is
1059            ! essentially diag(total_albedo) += matmul(transpose(v_matrix),
1060            ! diag(total_albedo_below)).
1061            do jreg = 1,nreg
1062              do jreg2 = 1,nreg
1063                total_albedo(:,jreg,jreg,jlev) &
1064                     &  = total_albedo(:,jreg,jreg,jlev) &
1065                     &  + total_albedo_below(:,jreg2,jreg2) &
1066                     &  * v_matrix(jreg2,jreg,jlev,jcol)
1067                total_albedo_direct(:,jreg,jreg,jlev) &
1068                     &  = total_albedo_direct(:,jreg,jreg,jlev) &
1069                     &  + total_albedo_below_direct(:,jreg2,jreg2) &
1070                     &  * v_matrix(jreg2,jreg,jlev,jcol)
1071              end do
1072            end do
1073
1074          else
1075            ! "Explicit entrapment"
1076
1077            do jreg2 = 1,nreg
1078              ! Loop through each region in the lower layer. For one
1079              ! of the regions in the lower layer, we are imagining it
1080              ! to be divided into "nreg" subregions that map onto the
1081              ! regions in the upper layer. The rate of exchange
1082              ! between these subregions is computed via a coupled
1083              ! differential equation written in terms of a singular
1084              ! exchange matrix (there are only terms for the exchange
1085              ! between subregions, but no propagation effects since
1086              ! we already know the albedo of this region). This is
1087              ! solved using the matrix-exponential method.
1088
1089              ! Use the following array for the transfer of either
1090              ! diffuse or direct radiation (despite the name), per
1091              ! unit horizontal distance travelled
1092              transfer_rate_diffuse = 0.0_jprb
1093
1094              ! As we need to reference the layer above the interface,
1095              ! don't do the following on the highest layer
1096              if (jlev > 1) then
1097
1098                ! Given a horizontal migration distance, there is
1099                ! still uncertainty about how much entrapment occurs
1100                ! associated with how one assumes cloud boundaries
1101                ! line up in adjacent layers. "overhang_factor"
1102                ! can be varied between 0.0 (the boundaries line up to
1103                ! the greatest extent possible given the overlap
1104                ! parameter) and 1.0 (the boundaries line up to the
1105                ! minimum extent possible); here this is used to
1106                ! produce a scaling factor for the transfer rate.
1107                transfer_scaling = 1.0_jprb - (1.0_jprb - config%overhang_factor) &
1108                     &  * cloud%overlap_param(jcol,jlev-1) &
1109                     &  * min(region_fracs(jreg2,jlev,jcol),region_fracs(jreg2,jlev-1,jcol)) &
1110                     &  / max(config%cloud_fraction_threshold, region_fracs(jreg2,jlev,jcol))
1111
1112                do jreg = 1, nreg-1
1113                  ! Compute lateral transfer rates from region jreg to
1114                  ! jreg+1 as before, but without length scale which
1115                  ! is wavelength dependent.
1116
1117                  ! Recall that overlap indexing is
1118                  ! u_matrix(upper_region, lower_region, level,
1119                  ! column).
1120                  transfer_rate_diffuse(jreg,jreg+1) = transfer_scaling &
1121                       &  * edge_length(jreg,jlev-1) / max(u_matrix(jreg,jreg2,jlev,jcol),1.0e-5_jprb)
1122                  ! Compute transfer rates from region jreg+1 to jreg
1123                  transfer_rate_diffuse(jreg+1,jreg) = transfer_scaling &
1124                       &  * edge_length(jreg,jlev-1) / max(u_matrix(jreg+1,jreg2,jlev,jcol),1.0e-5_jprb)
1125                end do
1126             
1127                ! Compute transfer rates directly between regions 1
1128                ! and 3 (not used below)
1129                if (edge_length(3,jlev) > 0.0_jprb) then
1130                  transfer_rate_diffuse(1,3) = transfer_scaling &
1131                       &  * edge_length(3,jlev-1) / max(u_matrix(1,jreg2,jlev,jcol),1.0e-5_jprb)
1132                  transfer_rate_diffuse(3,1) = transfer_scaling &
1133                       &  * edge_length(3,jlev-1) / max(u_matrix(3,jreg2,jlev,jcol),1.0e-5_jprb)
1134                end if
1135              end if
1136
1137              ! Compute matrix of exchange coefficients
1138              entrapment = 0.0_jprb
1139              inv_effective_size = min(cloud%inv_cloud_effective_size(jcol,jlev-1), &
1140                   &                   1.0_jprb/config%min_cloud_effective_size)
1141              do jreg = 1,nreg-1
1142                ! Diffuse transport down and up with one random
1143                ! scattering event
1144                if (config%i_3d_sw_entrapment == IEntrapmentExplicit) then
1145                  fractal_factor = 1.0_jprb / sqrt(max(1.0_jprb, 2.5_jprb*x_diffuse(:,jreg2) &
1146                       &                                         * inv_effective_size))
1147                  entrapment(:,jreg+1,jreg) = entrapment(:,jreg+1,jreg) &
1148                       &  + transfer_rate_diffuse(jreg,jreg+1)*x_diffuse(:,jreg2) &
1149                       &  * fractal_factor
1150                  entrapment(:,jreg,jreg+1) = entrapment(:,jreg,jreg+1) &
1151                       &  + transfer_rate_diffuse(jreg+1,jreg)*x_diffuse(:,jreg2) &
1152                       &  * fractal_factor
1153                else
1154                  entrapment(:,jreg+1,jreg) = entrapment(:,jreg+1,jreg) &
1155                       &  + transfer_rate_diffuse(jreg,jreg+1)*x_diffuse(:,jreg2)
1156                  entrapment(:,jreg,jreg+1) = entrapment(:,jreg,jreg+1) &
1157                       &  + transfer_rate_diffuse(jreg+1,jreg)*x_diffuse(:,jreg2)                 
1158                end if
1159                entrapment(:,jreg,jreg) = entrapment(:,jreg,jreg) &
1160                     &  - entrapment(:,jreg+1,jreg)
1161                entrapment(:,jreg+1,jreg+1) = entrapment(:,jreg+1,jreg+1) &
1162                     &  - entrapment(:,jreg,jreg+1)
1163              end do
1164
1165              ! If rate of exchange is excessive the expm can throw a
1166              ! floating point exception, even if it tends towards a
1167              ! trival limit, so we cap the maximum input to expm by
1168              ! scaling down if necessary
1169              do jg = 1,ng
1170                max_entr = -min(entrapment(jg,1,1),entrapment(jg,2,2))
1171                if (max_entr > config%max_cloud_od) then
1172                  ! Scale down all inputs for this g point
1173                  entrapment(jg,:,:) = entrapment(jg,:,:) * (config%max_cloud_od/max_entr)
1174                end if
1175              end do
1176
1177              ! Since the matrix to be exponentiated has a simple
1178              ! structure we may use a faster method described in the
1179              ! appendix of Hogan et al. (GMD 2018)
1180#define USE_FAST_EXPM_EXCHANGE 1
1181#ifdef USE_FAST_EXPM_EXCHANGE
1182              if (nreg == 2) then
1183                call fast_expm_exchange(ng, ng, entrapment(:,2,1), entrapment(:,1,2), &
1184                     &                  albedo_part)
1185              else
1186                call fast_expm_exchange(ng, ng, entrapment(:,2,1), entrapment(:,1,2), &
1187                     &                          entrapment(:,3,2), entrapment(:,2,3), &
1188                     &                  albedo_part)
1189              end if
1190#else
1191              ! Use matrix exponential to compute rate of exchange
1192              albedo_part = entrapment
1193              call expm(ng, ng, nreg, albedo_part, IMatrixPatternDense)
1194              n_calls_expm = n_calls_expm + ng
1195#endif
1196
1197#ifndef EXPLICIT_EDGE_ENTRAPMENT
1198              ! Scale to get the contribution to the diffuse albedo
1199              do jreg3 = 1,nreg
1200                do jreg = 1,nreg
1201                  albedo_part(:,jreg3,jreg) = albedo_part(:,jreg3,jreg) &
1202                       &  * v_matrix(jreg2,jreg,jlev,jcol) * total_albedo_below(:,jreg2,jreg2)
1203                end do
1204              end do
1205#else
1206              ! The following is an experimental treatment that tries
1207              ! to explicitly account for the horizontal distance
1208              ! traveled by radiation that passes through cloud sides
1209              entrapment = albedo_part
1210              albedo_part = 0.0_jprb
1211              ! Scale to get the contribution to the diffuse albedo
1212              do jreg3 = 1,nreg     ! TO upper region
1213                do jreg = 1,nreg    ! FROM upper region
1214                  transfer_scaling = 1.0_jprb - (1.0_jprb - config%overhang_factor) &
1215                       &  * cloud%overlap_param(jcol,jlev-1) &
1216                       &  * min(region_fracs(jreg,jlev,jcol), region_fracs(jreg,jlev,jcol)) &
1217                       &  / max(config%cloud_fraction_threshold, region_fracs(jreg,jlev,jcol))
1218                  do jreg4 = 1,nreg ! VIA first lower region (jreg2 is second lower region)
1219                    if (.not. (jreg4 == jreg .and. jreg4 /= jreg2)) then
1220                      albedo_part(:,jreg3,jreg) = albedo_part(:,jreg3,jreg) + entrapment(:,jreg3,jreg) &
1221                           &  * v_matrix(jreg4,jreg,jlev,jcol) * total_albedo_below(:,jreg2,jreg4)
1222                    else
1223                      albedo_part(:,jreg3,jreg) = albedo_part(:,jreg3,jreg) &
1224                           &  + v_matrix(jreg4,jreg,jlev,jcol) * total_albedo_below(:,jreg2,jreg4) &
1225                           &  * (transfer_scaling * entrapment(:,jreg3,jreg) &
1226                           &    +((1.0_jprb-transfer_scaling) * entrapment(:,jreg3,jreg2)))
1227                    end if
1228                  end do
1229                end do
1230              end do
1231#endif
1232
1233              ! Increment diffuse albedo
1234              total_albedo(:,:,:,jlev) = total_albedo(:,:,:,jlev) + albedo_part
1235
1236              ! Now do the same for the direct albedo
1237              entrapment = 0.0_jprb
1238              do jreg = 1,nreg-1
1239                ! Direct transport down and diffuse up with one random
1240                ! scattering event
1241                if (config%i_3d_sw_entrapment == IEntrapmentExplicit) then
1242                  fractal_factor = 1.0_jprb / sqrt(max(1.0_jprb, 2.5_jprb*x_direct(:,jreg2) &
1243                       &                                         * inv_effective_size))
1244                  entrapment(:,jreg+1,jreg) = entrapment(:,jreg+1,jreg) &
1245                       &  + transfer_rate_diffuse(jreg,jreg+1)*x_direct(:,jreg2) &
1246                       &  * fractal_factor
1247                  entrapment(:,jreg,jreg+1) = entrapment(:,jreg,jreg+1) &
1248                       &  + transfer_rate_diffuse(jreg+1,jreg)*x_direct(:,jreg2) &
1249                       &  * fractal_factor
1250                else
1251                  entrapment(:,jreg+1,jreg) = entrapment(:,jreg+1,jreg) &
1252                       &  + transfer_rate_diffuse(jreg,jreg+1)*x_direct(:,jreg2)
1253                  entrapment(:,jreg,jreg+1) = entrapment(:,jreg,jreg+1) &
1254                       &  + transfer_rate_diffuse(jreg+1,jreg)*x_direct(:,jreg2)
1255                end if
1256                entrapment(:,jreg,jreg) = entrapment(:,jreg,jreg) &
1257                     &  - entrapment(:,jreg+1,jreg)
1258                entrapment(:,jreg+1,jreg+1) = entrapment(:,jreg+1,jreg+1) &
1259                     &  - entrapment(:,jreg,jreg+1)
1260              end do
1261
1262              ! If rate of exchange is excessive the expm can throw a
1263              ! floating point exception, even if it tends towards a
1264              ! trival limit, so we cap the maximum input to expm by
1265              ! scaling down if necessary
1266              do jg = 1,ng
1267                max_entr = -min(entrapment(jg,1,1),entrapment(jg,2,2))
1268                if (max_entr > config%max_cloud_od) then
1269                  ! Scale down all inputs for this g point
1270                  entrapment(jg,:,:) = entrapment(jg,:,:) * (config%max_cloud_od/max_entr)
1271                end if
1272              end do
1273
1274
1275#ifdef USE_FAST_EXPM_EXCHANGE
1276              if (nreg == 2) then
1277                call fast_expm_exchange(ng, ng, entrapment(:,2,1), entrapment(:,1,2), &
1278                     &                  albedo_part)
1279              else
1280                call fast_expm_exchange(ng, ng, entrapment(:,2,1), entrapment(:,1,2), &
1281                     &                          entrapment(:,3,2), entrapment(:,2,3), &
1282                     &                  albedo_part)
1283              end if
1284#else
1285              albedo_part = entrapment
1286              call expm(ng, ng, nreg, albedo_part, IMatrixPatternDense)
1287              n_calls_expm = n_calls_expm + ng
1288#endif
1289
1290#ifndef EXPLICIT_EDGE_ENTRAPMENT
1291              do jreg3 = 1,nreg
1292                do jreg = 1,nreg
1293                  albedo_part(:,jreg3,jreg) = albedo_part(:,jreg3,jreg) &
1294                       &  * v_matrix(jreg2,jreg,jlev,jcol) * total_albedo_below_direct(:,jreg2,jreg2)
1295                end do
1296              end do
1297#else
1298              entrapment = albedo_part
1299              albedo_part = 0.0_jprb
1300              do jreg3 = 1,nreg
1301                do jreg = 1,nreg
1302                  transfer_scaling = 1.0_jprb - (1.0_jprb - config%overhang_factor) &
1303                       &  * cloud%overlap_param(jcol,jlev-1) &
1304                       &  * min(region_fracs(jreg,jlev,jcol), region_fracs(jreg,jlev-1,jcol)) &
1305                       &  / max(config%cloud_fraction_threshold, region_fracs(jreg,jlev,jcol))
1306                  do jreg4 = 1,nreg
1307                    if (.not. (jreg4 == jreg .and. jreg4 /= jreg2)) then
1308                     albedo_part(:,jreg3,jreg) = albedo_part(:,jreg3,jreg) + entrapment(:,jreg3,jreg) &
1309                           &  * v_matrix(jreg4,jreg,jlev,jcol) * total_albedo_below_direct(:,jreg2,jreg4)
1310                    else
1311                      albedo_part(:,jreg3,jreg) = albedo_part(:,jreg3,jreg) &
1312                           &  + v_matrix(jreg4,jreg,jlev,jcol) * total_albedo_below_direct(:,jreg2,jreg4) &
1313                           &  * (transfer_scaling * entrapment(:,jreg3,jreg) &
1314                           &    +((1.0_jprb-transfer_scaling) * entrapment(:,jreg3,jreg2)))
1315                    end if
1316                  end do
1317                end do
1318              end do
1319
1320#endif
1321              ! Increment direct albedo
1322              total_albedo_direct(:,:,:,jlev) = total_albedo_direct(:,:,:,jlev) + albedo_part
1323
1324            end do
1325
1326          end if
1327        end if
1328
1329        if ((config%i_3d_sw_entrapment == IEntrapmentExplicitNonFractal &
1330             &  .or. config%i_3d_sw_entrapment == IEntrapmentExplicit) &
1331             &  .and. .not. (is_clear_sky_layer(jlev) .and. is_clear_sky_layer(jlev-1))) then
1332          ! Horizontal migration distances are averaged when
1333          ! applying overlap rules, so equation is
1334          ! x_above=matmul(transpose(v_matrix),x_below)
1335         
1336          ! We do this into temporary arrays...
1337          x_direct_above = 0.0_jprb
1338          x_diffuse_above = 0.0_jprb
1339         
1340          nregactive = nreg
1341          if (is_clear_sky_layer(jlev)) then
1342            nregactive = 1
1343          end if
1344
1345          do jreg = 1,nreg          ! Target layer (jlev-1)
1346            do jreg2 = 1,nregactive ! Current layer (jlev)
1347              x_direct_above(:,jreg) = x_direct_above(:,jreg) &
1348                   &  + x_direct(:,jreg2) * v_matrix(jreg2,jreg,jlev,jcol)
1349              x_diffuse_above(:,jreg) = x_diffuse_above(:,jreg) &
1350                   &  + x_diffuse(:,jreg2) * v_matrix(jreg2,jreg,jlev,jcol)
1351            end do
1352          end do
1353         
1354          !... then copy out of the temporary arrays
1355          x_direct = x_direct_above
1356          x_diffuse = x_diffuse_above
1357        end if
1358
1359      end do ! Reverse loop over levels
1360
1361      ! --------------------------------------------------------
1362      ! Section 5: Compute fluxes
1363      ! --------------------------------------------------------
1364
1365      ! Top-of-atmosphere fluxes into the regions of the top-most
1366      ! layer, zero since we assume no diffuse downwelling
1367      flux_dn_below = 0.0_jprb
1368      ! Direct downwelling flux (into a plane perpendicular to the
1369      ! sun) entering the top of each region in the top-most layer
1370      do jreg = 1,nreg
1371        direct_dn_below(:,jreg) = incoming_sw(:,jcol)*region_fracs(jreg,1,jcol)
1372      end do
1373      ! We're using flux_up_above as a container; actually its
1374      ! interpretation at top of atmosphere here is just 'below' the
1375      ! TOA interface, so using the regions of the first model layer
1376      flux_up_above = mat_x_vec(ng,ng,nreg,total_albedo_direct(:,:,:,1),direct_dn_below)
1377
1378      if (config%do_clear) then
1379        flux_dn_clear = 0.0_jprb
1380        direct_dn_clear(:) = incoming_sw(:,jcol)
1381        flux_up_clear = direct_dn_clear*total_albedo_clear_direct(:,1)
1382      end if
1383
1384      ! Store the TOA broadband fluxes
1385      flux%sw_up(jcol,1) = sum(sum(flux_up_above,1))
1386      flux%sw_dn(jcol,1) = mu0 * sum(direct_dn_clear(:))
1387      if (allocated(flux%sw_dn_direct)) then
1388        flux%sw_dn_direct(jcol,1) = flux%sw_dn(jcol,1)
1389      end if
1390      if (config%do_clear) then
1391        flux%sw_up_clear(jcol,1) = sum(flux_up_clear)
1392        flux%sw_dn_clear(jcol,1) = flux%sw_dn(jcol,1)
1393        if (allocated(flux%sw_dn_direct_clear)) then
1394          flux%sw_dn_direct_clear(jcol,1) = flux%sw_dn_clear(jcol,1)
1395        end if
1396      end if
1397
1398      ! Save the spectral fluxes if required
1399      if (config%do_save_spectral_flux) then
1400        call indexed_sum(sum(flux_up_above(:,:),2), &
1401             &           config%i_spec_from_reordered_g_sw, &
1402             &           flux%sw_up_band(:,jcol,1))
1403        call indexed_sum(sum(direct_dn_below(:,:),2), &
1404             &           config%i_spec_from_reordered_g_sw, &
1405             &           flux%sw_dn_band(:,jcol,1))
1406        flux%sw_dn_band(:,jcol,1) = mu0 * flux%sw_dn_band(:,jcol,1)
1407        if (allocated(flux%sw_dn_direct_band)) then
1408          flux%sw_dn_direct_band(:,jcol,1) = flux%sw_dn_band(:,jcol,1)
1409        end if
1410        if (config%do_clear) then
1411          flux%sw_dn_clear_band(:,jcol,1) = flux%sw_dn_band(:,jcol,1)
1412          call indexed_sum(flux_up_clear, &
1413               &           config%i_spec_from_reordered_g_sw, &
1414               &           flux%sw_up_clear_band(:,jcol,1))
1415          if (allocated(flux%sw_dn_direct_clear_band)) then
1416            flux%sw_dn_direct_clear_band(:,jcol,1) &
1417                 &   = flux%sw_dn_clear_band(:,jcol,1)
1418          end if
1419        end if
1420      end if
1421
1422      ! Final loop back down through the atmosphere to compute fluxes
1423      do jlev = 1,nlev
1424
1425#ifdef PRINT_ENTRAPMENT_DATA
1426        if (config%i_3d_sw_entrapment == IEntrapmentExplicitNonFractal &
1427             &  .or. config%i_3d_sw_entrapment == IEntrapmentExplicit) then
1428          ! Save downwelling direct and diffuse fluxes at the top of
1429          ! layer "jlev" in each of the regions of layer "jlev"
1430          if (nreg == 2) then
1431            write(102,'(i4,i4,4e14.6)') jcol, jlev, direct_dn_below(1,:), flux_dn_below(1,:)
1432          else
1433            write(102,'(i4,i4,6e14.6)') jcol, jlev, direct_dn_below(1,1:3), flux_dn_below(1,1:3)
1434          end if
1435        end if
1436#endif
1437
1438        ! Compute the solar downwelling "source" at the base of the
1439        ! layer due to scattering of the direct beam within it
1440        if (config%do_clear) then
1441          source_dn_clear = trans_dir_diff_clear(:,jlev)*direct_dn_clear
1442        end if
1443        source_dn(:,:) = mat_x_vec(ng,ng,nreg,trans_dir_diff(:,:,:,jlev),direct_dn_below, &
1444             &  is_clear_sky_layer(jlev))
1445
1446        ! Compute direct downwelling flux in each region at base of
1447        ! current layer
1448        if (config%do_clear) then
1449          direct_dn_clear = trans_dir_dir_clear(:,jlev)*direct_dn_clear
1450        end if
1451        direct_dn_above = mat_x_vec(ng,ng,nreg,trans_dir_dir(:,:,:,jlev),direct_dn_below, &
1452             &  is_clear_sky_layer(jlev))
1453
1454        ! Integrate downwelling direct flux across spectrum and
1455        ! regions, and store (the diffuse part will be added later)
1456        flux%sw_dn(jcol,jlev+1) = mu0 * sum(sum(direct_dn_above,1))
1457        if (allocated(flux%sw_dn_direct)) then
1458          flux%sw_dn_direct(jcol,jlev+1) = flux%sw_dn(jcol,jlev+1)
1459        end if
1460        if (config%do_clear) then
1461          flux%sw_dn_clear(jcol,jlev+1) = mu0 * sum(direct_dn_clear)
1462          if (allocated(flux%sw_dn_direct_clear)) then
1463            flux%sw_dn_direct_clear(jcol,jlev+1) &
1464                 &  = flux%sw_dn_clear(jcol,jlev+1)
1465          end if
1466        end if
1467
1468        if (config%do_save_spectral_flux) then
1469          call indexed_sum(sum(direct_dn_above,2), &
1470               &           config%i_spec_from_reordered_g_sw, &
1471               &           flux%sw_dn_band(:,jcol,jlev+1))
1472          flux%sw_dn_band(:,jcol,jlev+1) = mu0 * flux%sw_dn_band(:,jcol,jlev+1)
1473
1474          if (allocated(flux%sw_dn_direct_band)) then
1475            flux%sw_dn_direct_band(:,jcol,jlev+1) &
1476                 &   = flux%sw_dn_band(:,jcol,jlev+1)
1477          end if
1478          if (config%do_clear) then
1479            call indexed_sum(direct_dn_clear, &
1480                 &           config%i_spec_from_reordered_g_sw, &
1481                 &           flux%sw_dn_clear_band(:,jcol,jlev+1))
1482            flux%sw_dn_clear_band(:,jcol,jlev+1) = mu0 &
1483                 &   * flux%sw_dn_clear_band(:,jcol,jlev+1)
1484            if (allocated(flux%sw_dn_direct_clear_band)) then
1485              flux%sw_dn_direct_clear_band(:,jcol,jlev+1) &
1486                   &  = flux%sw_dn_clear_band(:,jcol,jlev+1)
1487            end if
1488          end if
1489        end if
1490
1491        if (config%do_clear) then
1492          ! Scalar operations for clear-sky fluxes
1493          flux_dn_clear(:) = (trans_clear(:,jlev)*flux_dn_clear(:) &
1494               &  + ref_clear(:,jlev)*total_albedo_clear_direct(:,jlev+1)*direct_dn_clear &
1495               &  + source_dn_clear) &
1496               &  / (1.0_jprb - ref_clear(:,jlev)*total_albedo_clear(:,jlev+1))
1497          flux_up_clear(:) = total_albedo_clear_direct(:,jlev+1)*direct_dn_clear &
1498               &  + total_albedo_clear(:,jlev+1)*flux_dn_clear
1499        end if
1500
1501        if (is_clear_sky_layer(jlev)) then
1502          ! Scalar operations for clear-sky layer
1503          flux_dn_above(:,1) = (transmittance(:,1,1,jlev)*flux_dn_below(:,1) &
1504               &  + reflectance(:,1,1,jlev)*total_albedo_direct(:,1,1,jlev+1)*direct_dn_above(:,1) &
1505               &  + source_dn(:,1)) &
1506               &  / (1.0_jprb - reflectance(:,1,1,jlev)*total_albedo(:,1,1,jlev+1))
1507          flux_dn_above(:,2:nreg) = 0.0_jprb
1508          flux_up_above(:,1) = total_albedo_direct(:,1,1,jlev+1)*direct_dn_above(:,1) &
1509               &  + total_albedo(:,1,1,jlev+1)*flux_dn_above(:,1)
1510          flux_up_above(:,2:nreg) = 0.0_jprb
1511        else
1512          ! Matrix operations for cloudy layer
1513          denominator = identity_minus_mat_x_mat(ng,ng,nreg,reflectance(:,:,:,jlev), &
1514               &  total_albedo(:,:,:,jlev+1))
1515          total_source = mat_x_vec(ng,ng,nreg,total_albedo_direct(:,:,:,jlev+1),direct_dn_above)
1516
1517          flux_dn_above = solve_vec(ng,ng,nreg,denominator, &
1518               &  mat_x_vec(ng,ng,nreg,transmittance(:,:,:,jlev),flux_dn_below) &
1519               &  + mat_x_vec(ng,ng,nreg,reflectance(:,:,:,jlev), total_source(:,:)) &
1520               &  + source_dn(:,:))
1521          flux_up_above = mat_x_vec(ng,ng,nreg,total_albedo(:,:,:,jlev+1), &
1522               &  flux_dn_above) + total_source(:,:)
1523        end if
1524
1525        ! Account for overlap rules in translating fluxes just above
1526        ! a layer interface to the values just below
1527        if (is_clear_sky_layer(jlev) .and. is_clear_sky_layer(jlev+1)) then
1528          ! Regions in current layer map directly on to regions in
1529          ! layer below
1530          flux_dn_below = flux_dn_above
1531          direct_dn_below = direct_dn_above
1532        else
1533          ! Apply downward overlap matrix to compute direct
1534          ! downwelling flux entering the top of each region in the
1535          ! layer below
1536          flux_dn_below = singlemat_x_vec(ng,ng,nreg,v_matrix(:,:,jlev+1,jcol), &
1537               &  flux_dn_above)
1538          direct_dn_below = singlemat_x_vec(ng,ng,nreg,v_matrix(:,:,jlev+1,jcol), &
1539               &  direct_dn_above)
1540        end if
1541
1542        ! Store the broadband fluxes
1543        flux%sw_up(jcol,jlev+1) = sum(sum(flux_up_above,1))
1544        flux%sw_dn(jcol,jlev+1) &
1545             &  = flux%sw_dn(jcol,jlev+1) + sum(sum(flux_dn_above,1))
1546        if (config%do_clear) then
1547          flux%sw_up_clear(jcol,jlev+1) = sum(flux_up_clear)
1548          flux%sw_dn_clear(jcol,jlev+1) &
1549               &  = flux%sw_dn_clear(jcol,jlev+1) + sum(flux_dn_clear)
1550        end if
1551
1552        ! Save the spectral fluxes if required
1553        if (config%do_save_spectral_flux) then
1554          call indexed_sum(sum(flux_up_above,2), &
1555               &           config%i_spec_from_reordered_g_sw, &
1556               &           flux%sw_up_band(:,jcol,jlev+1))
1557          call add_indexed_sum(sum(flux_dn_above,2), &
1558               &           config%i_spec_from_reordered_g_sw, &
1559               &           flux%sw_dn_band(:,jcol,jlev+1))
1560          if (config%do_clear) then
1561            call indexed_sum(flux_up_clear, &
1562                 &           config%i_spec_from_reordered_g_sw, &
1563                 &           flux%sw_up_clear_band(:,jcol,jlev+1))
1564            call add_indexed_sum(flux_dn_clear, &
1565                 &           config%i_spec_from_reordered_g_sw, &
1566                 &           flux%sw_dn_clear_band(:,jcol,jlev+1))
1567          end if
1568        end if
1569
1570      end do ! Final loop over levels
1571
1572      ! Store surface spectral fluxes, if required (after the end of
1573      ! the final loop over levels, the current values of these arrays
1574      ! will be the surface values)
1575      flux%sw_dn_diffuse_surf_g(:,jcol) = sum(flux_dn_above,2)
1576      flux%sw_dn_direct_surf_g(:,jcol)  = mu0 * sum(direct_dn_above,2)
1577      if (config%do_clear) then
1578        flux%sw_dn_diffuse_surf_clear_g(:,jcol) = flux_dn_clear
1579        flux%sw_dn_direct_surf_clear_g(:,jcol)  = mu0 * direct_dn_clear
1580      end if
1581
1582    end do ! Loop over columns
1583    if (config%iverbose >= 3) then
1584      write(nulout,*)
1585    end if
1586
1587    ! Report number of calls to each method of solving single-layer
1588    ! two-stream equations
1589    if (config%iverbose >= 4) then
1590      write(nulout,'(a,i0)') '  Matrix-exponential calls: ', n_calls_expm
1591      write(nulout,'(a,i0)') '  Meador-Weaver calls: ', n_calls_meador_weaver
1592    end if
1593
1594    if (lhook) call dr_hook('radiation_spartacus_sw:solver_spartacus_sw',1,hook_handle)
1595
1596  end subroutine solver_spartacus_sw
1597
1598
1599  ! Step the horizontal migration distances from the base of a layer
1600  ! to the top, accounting for the extra distance travelled within the
1601  ! layer
1602  subroutine step_migrations(ng, nreg, cloud_frac, &
1603       &  layer_depth, tan_diffuse_angle_3d, tan_sza, &
1604       &  reflectance, transmittance, ref_dir, trans_dir_dir, &
1605       &  trans_dir_diff, total_albedo_diff, total_albedo_dir, &
1606       &  x_diffuse, x_direct)
1607   
1608    use parkind1, only : jprb
1609
1610    implicit none
1611
1612    ! Inputs
1613
1614    ! Number of g points and regions
1615    integer, intent(in) :: ng, nreg
1616    ! Cloud fraction
1617    real(jprb), intent(in) :: cloud_frac
1618    ! Layer depth (m), tangent of diffuse zenith angle and tangent of
1619    ! solar zenith angle
1620    real(jprb), intent(in) :: layer_depth, tan_diffuse_angle_3d, tan_sza
1621    ! Reflectance and transmittance to diffuse downwelling radiation
1622    real(jprb), intent(in), dimension(ng, nreg, nreg) :: reflectance, transmittance
1623    ! Reflectance and transmittance to direct downwelling radiation
1624    real(jprb), intent(in), dimension(ng, nreg, nreg) :: ref_dir, trans_dir_dir
1625    ! Transmittance involving direct entering a layer from the top and
1626    ! diffuse leaving from the bottom
1627    real(jprb), intent(in), dimension(ng, nreg, nreg) :: trans_dir_diff
1628
1629    ! Total albedo of direct and diffuse radiation of the atmosphere
1630    ! below the layer in question
1631    real(jprb), intent(in), dimension(ng, nreg, nreg) &
1632         &  :: total_albedo_diff, total_albedo_dir
1633
1634    ! Inputs/outputs
1635
1636    ! Horizontal migration distance (m) of reflected light
1637    real(jprb), intent(inout), dimension(ng, nreg) :: x_diffuse, x_direct
1638
1639    ! Local variables
1640
1641    ! Top albedo, i.e. the albedo of the top of the layer assuming no
1642    ! lateral transport
1643    real(jprb), dimension(ng) :: top_albedo
1644
1645    ! Multiple-scattering amplitude enhancement
1646    real(jprb), dimension(ng) :: ms_enhancement
1647
1648    ! Multiple-scattering distance enhancement
1649    real(jprb), dimension(ng) :: x_enhancement
1650
1651
1652    real(jprb) :: x_layer_diffuse, x_layer_direct
1653    integer :: jreg, istartreg, iendreg
1654
1655    istartreg = 1
1656    iendreg   = nreg
1657
1658    if (cloud_frac <= 0.0_jprb) then
1659      ! Clear-sky layer: don't waste time on cloudy regions
1660      iendreg = 1
1661    else if (cloud_frac >= 1.0_jprb) then
1662      ! Overcast layer: don't waste time on clear region
1663      istartreg = 2
1664    end if
1665
1666    ! This is the mean horizontal distance travelled by diffuse
1667    ! radiation that travels from the top of a layer to the centre and
1668    ! is then scattered back up and out
1669    x_layer_diffuse = layer_depth * tan_diffuse_angle_3d/sqrt(2.0_jprb)
1670
1671    ! This is the mean horizontal distance travelled by direct
1672    ! radiation that travels from the top of a layer to the centre and
1673    ! is then scattered back up and out
1674    x_layer_direct  = layer_depth * sqrt(tan_sza*tan_sza &
1675         &                             + tan_diffuse_angle_3d*tan_diffuse_angle_3d) * 0.5_jprb
1676
1677    do jreg = istartreg,iendreg
1678      ! Geometric series enhancement due to multiple scattering: the
1679      ! amplitude enhancement is equal to the limit of
1680      ! T*[1+RA+(RA)^2+(RA)^3+...]
1681      ms_enhancement = transmittance(:,jreg,jreg) &
1682           &  / (1.0_jprb - reflectance(:,jreg,jreg)*total_albedo_diff(:,jreg,jreg))
1683      ! ...and the distance enhancement is approximately equal to the
1684      ! limit of T*[1+sqrt(2)*RA+sqrt(3)*(RA)^2+sqrt(4)*(RA)^3+...]
1685      x_enhancement = (1.0_jprb - reflectance(:,jreg,jreg)*total_albedo_diff(:,jreg,jreg))**(-1.5_jprb)
1686
1687      ! Horizontal migration of direct downwelling radiation
1688      top_albedo = max(1.0e-8_jprb, ref_dir(:,jreg,jreg) + ms_enhancement &
1689           &  * (trans_dir_diff(:,jreg,jreg)*total_albedo_diff(:,jreg,jreg) &
1690           &     +trans_dir_dir(:,jreg,jreg)*total_albedo_dir(:,jreg,jreg)))
1691      ! The following is approximate and has been found to
1692      ! occasionally go negative
1693      x_direct(:,jreg) = max(0.0_jprb, x_layer_direct &
1694           &  + ((trans_dir_diff(:,jreg,jreg)*total_albedo_diff(:,jreg,jreg)*x_enhancement &
1695           &      +trans_dir_dir(:,jreg,jreg)*total_albedo_dir(:,jreg,jreg)*(x_enhancement-1.0_jprb)) &
1696           &     *(x_diffuse(:,jreg)+x_layer_diffuse) &
1697           &    +trans_dir_dir(:,jreg,jreg)*total_albedo_dir(:,jreg,jreg) &
1698           &     *(x_direct(:,jreg)+x_layer_direct)) &
1699           &    * transmittance(:,jreg,jreg) / top_albedo)
1700
1701      ! Horizontal migration of diffuse downwelling radiation
1702      top_albedo = max(1.0e-8_jprb, reflectance(:,jreg,jreg) &
1703           &  + ms_enhancement*transmittance(:,jreg,jreg)*total_albedo_diff(:,jreg,jreg))
1704      x_diffuse(:,jreg) = x_layer_diffuse + x_enhancement*total_albedo_diff(:,jreg,jreg) &
1705           &  *(transmittance(:,jreg,jreg)*transmittance(:,jreg,jreg)) &
1706           &  * (x_diffuse(:,jreg) + x_layer_diffuse) / top_albedo
1707
1708    end do
1709    if (iendreg < nreg) then
1710      x_diffuse(:,iendreg+1:nreg)      = 0.0_jprb
1711      x_direct(:,iendreg+1:nreg)       = 0.0_jprb
1712    else if (istartreg == 2) then
1713      x_diffuse(:,1)      = 0.0_jprb
1714      x_direct(:,1)       = 0.0_jprb
1715    end if
1716
1717  end subroutine step_migrations
1718
1719end module radiation_spartacus_sw
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