| 1 | ! radiation_mcica_lw.F90 - Monte-Carlo Independent Column Approximation longtwave solver |
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| 2 | ! |
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| 3 | ! (C) Copyright 2015- ECMWF. |
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| 4 | ! |
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| 5 | ! This software is licensed under the terms of the Apache Licence Version 2.0 |
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| 6 | ! which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. |
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| 7 | ! |
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| 8 | ! In applying this licence, ECMWF does not waive the privileges and immunities |
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| 9 | ! granted to it by virtue of its status as an intergovernmental organisation |
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| 10 | ! nor does it submit to any jurisdiction. |
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| 11 | ! |
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| 12 | ! Author: Robin Hogan |
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| 13 | ! Email: r.j.hogan@ecmwf.int |
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| 14 | ! |
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| 15 | ! Modifications |
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| 16 | ! 2017-04-11 R. Hogan Receive emission/albedo rather than planck/emissivity |
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| 17 | ! 2017-04-22 R. Hogan Store surface fluxes at all g-points |
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| 18 | ! 2017-07-12 R. Hogan Call fast adding method if only clouds scatter |
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| 19 | ! 2017-10-23 R. Hogan Renamed single-character variables |
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| 20 | |
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| 21 | module radiation_mcica_lw |
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| 22 | |
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| 23 | public |
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| 24 | |
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| 25 | contains |
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| 26 | |
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| 27 | !--------------------------------------------------------------------- |
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| 28 | ! Longwave Monte Carlo Independent Column Approximation |
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| 29 | ! (McICA). This implementation performs a clear-sky and a cloudy-sky |
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| 30 | ! calculation, and then weights the two to get the all-sky fluxes |
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| 31 | ! according to the total cloud cover. This method reduces noise for |
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| 32 | ! low cloud cover situations, and exploits the clear-sky |
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| 33 | ! calculations that are usually performed for diagnostic purposes |
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| 34 | ! simultaneously. The cloud generator has been carefully written |
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| 35 | ! such that the stochastic cloud field satisfies the prescribed |
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| 36 | ! overlap parameter accounting for this weighting. |
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| 37 | subroutine solver_mcica_lw(nlev,istartcol,iendcol, & |
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| 38 | & config, single_level, cloud, & |
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| 39 | & od, ssa, g, od_cloud, ssa_cloud, g_cloud, planck_hl, & |
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| 40 | & emission, albedo, & |
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| 41 | & flux) |
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| 42 | |
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| 43 | use parkind1, only : jprb |
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| 44 | use yomhook, only : lhook, dr_hook, jphook |
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| 45 | |
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| 46 | use radiation_io, only : nulerr, radiation_abort |
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| 47 | use radiation_config, only : config_type |
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| 48 | use radiation_single_level, only : single_level_type |
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| 49 | use radiation_cloud, only : cloud_type |
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| 50 | use radiation_flux, only : flux_type |
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| 51 | use radiation_two_stream, only : calc_ref_trans_lw, & |
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| 52 | & calc_no_scattering_transmittance_lw |
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| 53 | use radiation_adding_ica_lw, only : adding_ica_lw, fast_adding_ica_lw, & |
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| 54 | & calc_fluxes_no_scattering_lw |
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| 55 | use radiation_lw_derivatives, only : calc_lw_derivatives_ica, modify_lw_derivatives_ica |
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| 56 | use radiation_cloud_generator, only: cloud_generator |
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| 57 | |
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| 58 | implicit none |
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| 59 | |
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| 60 | ! Inputs |
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| 61 | integer, intent(in) :: nlev ! number of model levels |
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| 62 | integer, intent(in) :: istartcol, iendcol ! range of columns to process |
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| 63 | type(config_type), intent(in) :: config |
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| 64 | type(single_level_type), intent(in) :: single_level |
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| 65 | type(cloud_type), intent(in) :: cloud |
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| 66 | |
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| 67 | ! Gas and aerosol optical depth, single-scattering albedo and |
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| 68 | ! asymmetry factor at each longwave g-point |
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| 69 | real(jprb), intent(in), dimension(config%n_g_lw, nlev, istartcol:iendcol) :: & |
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| 70 | & od |
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| 71 | real(jprb), intent(in), dimension(config%n_g_lw_if_scattering, nlev, istartcol:iendcol) :: & |
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| 72 | & ssa, g |
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| 73 | |
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| 74 | ! Cloud and precipitation optical depth, single-scattering albedo and |
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| 75 | ! asymmetry factor in each longwave band |
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| 76 | real(jprb), intent(in), dimension(config%n_bands_lw,nlev,istartcol:iendcol) :: & |
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| 77 | & od_cloud |
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| 78 | real(jprb), intent(in), dimension(config%n_bands_lw_if_scattering, & |
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| 79 | & nlev,istartcol:iendcol) :: ssa_cloud, g_cloud |
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| 80 | |
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| 81 | ! Planck function at each half-level and the surface |
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| 82 | real(jprb), intent(in), dimension(config%n_g_lw,nlev+1,istartcol:iendcol) :: & |
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| 83 | & planck_hl |
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| 84 | |
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| 85 | ! Emission (Planck*emissivity) and albedo (1-emissivity) at the |
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| 86 | ! surface at each longwave g-point |
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| 87 | real(jprb), intent(in), dimension(config%n_g_lw, istartcol:iendcol) :: emission, albedo |
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| 88 | |
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| 89 | ! Output |
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| 90 | type(flux_type), intent(inout):: flux |
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| 91 | |
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| 92 | ! Local variables |
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| 93 | |
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| 94 | ! Diffuse reflectance and transmittance for each layer in clear |
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| 95 | ! and all skies |
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| 96 | real(jprb), dimension(config%n_g_lw, nlev) :: ref_clear, trans_clear, reflectance, transmittance |
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| 97 | |
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| 98 | ! Emission by a layer into the upwelling or downwelling diffuse |
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| 99 | ! streams, in clear and all skies |
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| 100 | real(jprb), dimension(config%n_g_lw, nlev) :: source_up_clear, source_dn_clear, source_up, source_dn |
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| 101 | |
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| 102 | ! Fluxes per g point |
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| 103 | real(jprb), dimension(config%n_g_lw, nlev+1) :: flux_up, flux_dn |
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| 104 | real(jprb), dimension(config%n_g_lw, nlev+1) :: flux_up_clear, flux_dn_clear |
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| 105 | |
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| 106 | ! Combined gas+aerosol+cloud optical depth, single scattering |
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| 107 | ! albedo and asymmetry factor |
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| 108 | real(jprb), dimension(config%n_g_lw) :: od_total, ssa_total, g_total |
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| 109 | |
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| 110 | ! Combined scattering optical depth |
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| 111 | real(jprb) :: scat_od, scat_od_total(config%n_g_lw) |
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| 112 | |
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| 113 | ! Optical depth scaling from the cloud generator, zero indicating |
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| 114 | ! clear skies |
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| 115 | real(jprb), dimension(config%n_g_lw,nlev) :: od_scaling |
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| 116 | |
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| 117 | ! Modified optical depth after McICA scaling to represent cloud |
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| 118 | ! inhomogeneity |
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| 119 | real(jprb), dimension(config%n_g_lw) :: od_cloud_new |
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| 120 | |
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| 121 | ! Total cloud cover output from the cloud generator |
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| 122 | real(jprb) :: total_cloud_cover |
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| 123 | |
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| 124 | ! Identify clear-sky layers |
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| 125 | logical :: is_clear_sky_layer(nlev) |
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| 126 | |
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| 127 | ! Index of the highest cloudy layer |
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| 128 | integer :: i_cloud_top |
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| 129 | |
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| 130 | ! Number of g points |
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| 131 | integer :: ng |
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| 132 | |
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| 133 | ! Loop indices for level, column and g point |
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| 134 | integer :: jlev, jcol, jg |
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| 135 | |
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| 136 | real(jphook) :: hook_handle |
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| 137 | |
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| 138 | if (lhook) call dr_hook('radiation_mcica_lw:solver_mcica_lw',0,hook_handle) |
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| 139 | |
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| 140 | if (.not. config%do_clear) then |
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| 141 | write(nulerr,'(a)') '*** Error: longwave McICA requires clear-sky calculation to be performed' |
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| 142 | call radiation_abort() |
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| 143 | end if |
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| 144 | |
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| 145 | ng = config%n_g_lw |
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| 146 | |
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| 147 | ! Loop through columns |
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| 148 | do jcol = istartcol,iendcol |
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| 149 | |
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| 150 | ! Clear-sky calculation |
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| 151 | if (config%do_lw_aerosol_scattering) then |
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| 152 | ! Scattering case: first compute clear-sky reflectance, |
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| 153 | ! transmittance etc at each model level |
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| 154 | call calc_ref_trans_lw(ng*nlev, & |
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| 155 | & od(:,:,jcol), ssa(:,:,jcol), g(:,:,jcol), & |
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| 156 | & planck_hl(:,1:nlev,jcol), planck_hl(:,2:nlev+1,jcol), & |
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| 157 | & ref_clear, trans_clear, & |
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| 158 | & source_up_clear, source_dn_clear) |
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| 159 | ! Then use adding method to compute fluxes |
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| 160 | call adding_ica_lw(ng, nlev, & |
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| 161 | & ref_clear, trans_clear, source_up_clear, source_dn_clear, & |
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| 162 | & emission(:,jcol), albedo(:,jcol), & |
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| 163 | & flux_up_clear, flux_dn_clear) |
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| 164 | else |
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| 165 | ! Non-scattering case: use simpler functions for |
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| 166 | ! transmission and emission |
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| 167 | call calc_no_scattering_transmittance_lw(ng*nlev, od(:,:,jcol), & |
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| 168 | & planck_hl(:,1:nlev,jcol), planck_hl(:,2:nlev+1, jcol), & |
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| 169 | & trans_clear, source_up_clear, source_dn_clear) |
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| 170 | ! Ensure that clear-sky reflectance is zero since it may be |
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| 171 | ! used in cloudy-sky case |
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| 172 | ref_clear = 0.0_jprb |
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| 173 | ! Simpler down-then-up method to compute fluxes |
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| 174 | call calc_fluxes_no_scattering_lw(ng, nlev, & |
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| 175 | & trans_clear, source_up_clear, source_dn_clear, & |
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| 176 | & emission(:,jcol), albedo(:,jcol), & |
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| 177 | & flux_up_clear, flux_dn_clear) |
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| 178 | end if |
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| 179 | |
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| 180 | ! Sum over g-points to compute broadband fluxes |
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| 181 | flux%lw_up_clear(jcol,:) = sum(flux_up_clear,1) |
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| 182 | flux%lw_dn_clear(jcol,:) = sum(flux_dn_clear,1) |
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| 183 | ! Store surface spectral downwelling fluxes |
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| 184 | flux%lw_dn_surf_clear_g(:,jcol) = flux_dn_clear(:,nlev+1) |
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| 185 | |
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| 186 | ! Do cloudy-sky calculation; add a prime number to the seed in |
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| 187 | ! the longwave |
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| 188 | call cloud_generator(ng, nlev, config%i_overlap_scheme, & |
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| 189 | & single_level%iseed(jcol) + 997, & |
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| 190 | & config%cloud_fraction_threshold, & |
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| 191 | & cloud%fraction(jcol,:), cloud%overlap_param(jcol,:), & |
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| 192 | & config%cloud_inhom_decorr_scaling, cloud%fractional_std(jcol,:), & |
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| 193 | & config%pdf_sampler, od_scaling, total_cloud_cover, & |
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| 194 | & use_beta_overlap=config%use_beta_overlap, & |
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| 195 | & use_vectorizable_generator=config%use_vectorizable_generator) |
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| 196 | |
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| 197 | ! Store total cloud cover |
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| 198 | flux%cloud_cover_lw(jcol) = total_cloud_cover |
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| 199 | |
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| 200 | if (total_cloud_cover >= config%cloud_fraction_threshold) then |
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| 201 | ! Total-sky calculation |
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| 202 | |
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| 203 | is_clear_sky_layer = .true. |
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| 204 | i_cloud_top = nlev+1 |
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| 205 | do jlev = 1,nlev |
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| 206 | ! Compute combined gas+aerosol+cloud optical properties |
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| 207 | if (cloud%fraction(jcol,jlev) >= config%cloud_fraction_threshold) then |
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| 208 | is_clear_sky_layer(jlev) = .false. |
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| 209 | ! Get index to the first cloudy layer from the top |
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| 210 | if (i_cloud_top > jlev) then |
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| 211 | i_cloud_top = jlev |
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| 212 | end if |
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| 213 | |
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| 214 | do jg = 1,ng |
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| 215 | od_cloud_new(jg) = od_scaling(jg,jlev) & |
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| 216 | & * od_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) |
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| 217 | od_total(jg) = od(jg,jlev,jcol) + od_cloud_new(jg) |
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| 218 | ssa_total(jg) = 0.0_jprb |
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| 219 | g_total(jg) = 0.0_jprb |
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| 220 | end do |
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| 221 | |
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| 222 | if (config%do_lw_cloud_scattering) then |
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| 223 | ! Scattering case: calculate reflectance and |
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| 224 | ! transmittance at each model level |
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| 225 | |
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| 226 | if (config%do_lw_aerosol_scattering) then |
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| 227 | ! In single precision we need to protect against the |
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| 228 | ! case that od_total > 0.0 and ssa_total > 0.0 but |
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| 229 | ! od_total*ssa_total == 0 due to underflow |
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| 230 | do jg = 1,ng |
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| 231 | if (od_total(jg) > 0.0_jprb) then |
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| 232 | scat_od_total(jg) = ssa(jg,jlev,jcol)*od(jg,jlev,jcol) & |
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| 233 | & + ssa_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & |
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| 234 | & * od_cloud_new(jg) |
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| 235 | ssa_total(jg) = scat_od_total(jg) / od_total(jg) |
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| 236 | |
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| 237 | if (scat_od_total(jg) > 0.0_jprb) then |
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| 238 | g_total(jg) = (g(jg,jlev,jcol)*ssa(jg,jlev,jcol)*od(jg,jlev,jcol) & |
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| 239 | & + g_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & |
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| 240 | & * ssa_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & |
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| 241 | & * od_cloud_new(jg)) & |
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| 242 | & / scat_od_total(jg) |
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| 243 | end if |
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| 244 | end if |
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| 245 | end do |
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| 246 | |
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| 247 | else |
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| 248 | |
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| 249 | do jg = 1,ng |
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| 250 | if (od_total(jg) > 0.0_jprb) then |
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| 251 | scat_od = ssa_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & |
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| 252 | & * od_cloud_new(jg) |
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| 253 | ssa_total(jg) = scat_od / od_total(jg) |
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| 254 | if (scat_od > 0.0_jprb) then |
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| 255 | g_total(jg) = g_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & |
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| 256 | & * ssa_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & |
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| 257 | & * od_cloud_new(jg) / scat_od |
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| 258 | end if |
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| 259 | end if |
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| 260 | end do |
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| 261 | |
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| 262 | end if |
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| 263 | |
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| 264 | ! Compute cloudy-sky reflectance, transmittance etc at |
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| 265 | ! each model level |
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| 266 | call calc_ref_trans_lw(ng, & |
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| 267 | & od_total, ssa_total, g_total, & |
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| 268 | & planck_hl(:,jlev,jcol), planck_hl(:,jlev+1,jcol), & |
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| 269 | & reflectance(:,jlev), transmittance(:,jlev), & |
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| 270 | & source_up(:,jlev), source_dn(:,jlev)) |
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| 271 | else |
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| 272 | ! No-scattering case: use simpler functions for |
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| 273 | ! transmission and emission |
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| 274 | call calc_no_scattering_transmittance_lw(ng, od_total, & |
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| 275 | & planck_hl(:,jlev,jcol), planck_hl(:,jlev+1, jcol), & |
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| 276 | & transmittance(:,jlev), source_up(:,jlev), source_dn(:,jlev)) |
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| 277 | end if |
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| 278 | |
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| 279 | else |
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| 280 | ! Clear-sky layer: copy over clear-sky values |
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| 281 | reflectance(:,jlev) = ref_clear(:,jlev) |
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| 282 | transmittance(:,jlev) = trans_clear(:,jlev) |
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| 283 | source_up(:,jlev) = source_up_clear(:,jlev) |
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| 284 | source_dn(:,jlev) = source_dn_clear(:,jlev) |
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| 285 | end if |
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| 286 | end do |
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| 287 | |
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| 288 | if (config%do_lw_aerosol_scattering) then |
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| 289 | ! Use adding method to compute fluxes for an overcast sky, |
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| 290 | ! allowing for scattering in all layers |
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| 291 | call adding_ica_lw(ng, nlev, reflectance, transmittance, source_up, source_dn, & |
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| 292 | & emission(:,jcol), albedo(:,jcol), & |
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| 293 | & flux_up, flux_dn) |
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| 294 | else if (config%do_lw_cloud_scattering) then |
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| 295 | ! Use adding method to compute fluxes but optimize for the |
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| 296 | ! presence of clear-sky layers |
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| 297 | call fast_adding_ica_lw(ng, nlev, reflectance, transmittance, source_up, source_dn, & |
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| 298 | & emission(:,jcol), albedo(:,jcol), & |
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| 299 | & is_clear_sky_layer, i_cloud_top, flux_dn_clear, & |
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| 300 | & flux_up, flux_dn) |
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| 301 | else |
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| 302 | ! Simpler down-then-up method to compute fluxes |
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| 303 | call calc_fluxes_no_scattering_lw(ng, nlev, & |
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| 304 | & transmittance, source_up, source_dn, emission(:,jcol), albedo(:,jcol), & |
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| 305 | & flux_up, flux_dn) |
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| 306 | end if |
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| 307 | |
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| 308 | ! Store overcast broadband fluxes |
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| 309 | flux%lw_up(jcol,:) = sum(flux_up,1) |
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| 310 | flux%lw_dn(jcol,:) = sum(flux_dn,1) |
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| 311 | |
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| 312 | ! Cloudy flux profiles currently assume completely overcast |
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| 313 | ! skies; perform weighted average with clear-sky profile |
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| 314 | flux%lw_up(jcol,:) = total_cloud_cover *flux%lw_up(jcol,:) & |
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| 315 | & + (1.0_jprb - total_cloud_cover)*flux%lw_up_clear(jcol,:) |
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| 316 | flux%lw_dn(jcol,:) = total_cloud_cover *flux%lw_dn(jcol,:) & |
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| 317 | & + (1.0_jprb - total_cloud_cover)*flux%lw_dn_clear(jcol,:) |
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| 318 | ! Store surface spectral downwelling fluxes |
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| 319 | flux%lw_dn_surf_g(:,jcol) = total_cloud_cover*flux_dn(:,nlev+1) & |
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| 320 | & + (1.0_jprb - total_cloud_cover)*flux%lw_dn_surf_clear_g(:,jcol) |
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| 321 | |
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| 322 | ! Compute the longwave derivatives needed by Hogan and Bozzo |
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| 323 | ! (2015) approximate radiation update scheme |
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| 324 | if (config%do_lw_derivatives) then |
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| 325 | call calc_lw_derivatives_ica(ng, nlev, jcol, transmittance, flux_up(:,nlev+1), & |
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| 326 | & flux%lw_derivatives) |
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| 327 | if (total_cloud_cover < 1.0_jprb - config%cloud_fraction_threshold) then |
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| 328 | ! Modify the existing derivative with the contribution from the clear sky |
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| 329 | call modify_lw_derivatives_ica(ng, nlev, jcol, trans_clear, flux_up_clear(:,nlev+1), & |
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| 330 | & 1.0_jprb-total_cloud_cover, flux%lw_derivatives) |
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| 331 | end if |
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| 332 | end if |
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| 333 | |
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| 334 | else |
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| 335 | ! No cloud in profile and clear-sky fluxes already |
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| 336 | ! calculated: copy them over |
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| 337 | flux%lw_up(jcol,:) = flux%lw_up_clear(jcol,:) |
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| 338 | flux%lw_dn(jcol,:) = flux%lw_dn_clear(jcol,:) |
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| 339 | flux%lw_dn_surf_g(:,jcol) = flux%lw_dn_surf_clear_g(:,jcol) |
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| 340 | if (config%do_lw_derivatives) then |
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| 341 | call calc_lw_derivatives_ica(ng, nlev, jcol, trans_clear, flux_up_clear(:,nlev+1), & |
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| 342 | & flux%lw_derivatives) |
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| 343 | |
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| 344 | end if |
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| 345 | end if ! Cloud is present in profile |
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| 346 | end do |
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| 347 | |
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| 348 | if (lhook) call dr_hook('radiation_mcica_lw:solver_mcica_lw',1,hook_handle) |
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| 349 | |
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| 350 | end subroutine solver_mcica_lw |
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| 351 | |
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| 352 | end module radiation_mcica_lw |
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