[3908] | 1 | ! radiation_ice_optics_fu.F90 - Fu's scheme for ice optical properties |
---|
| 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 | ! 2020-08-10 R. Hogan Bounded re to be <= 100um and g to be < 1.0 |
---|
| 17 | |
---|
| 18 | module radiation_ice_optics_fu |
---|
| 19 | |
---|
| 20 | use parkind1, only : jprb |
---|
| 21 | |
---|
| 22 | implicit none |
---|
| 23 | public |
---|
| 24 | |
---|
| 25 | ! The number of ice coefficients depends on the parameterization |
---|
| 26 | integer, parameter :: NIceOpticsCoeffsFuSW = 10 |
---|
| 27 | integer, parameter :: NIceOpticsCoeffsFuLW = 11 |
---|
| 28 | |
---|
| 29 | ! Limits based on the range of validity of the parameterizations |
---|
| 30 | real(jprb), parameter :: MaxAsymmetryFactor = 1.0_jprb - 10.0_jprb*epsilon(1.0_jprb) |
---|
| 31 | real(jprb), parameter :: MaxEffectiveRadius = 100.0e-6_jprb ! metres |
---|
| 32 | |
---|
| 33 | contains |
---|
| 34 | |
---|
| 35 | !--------------------------------------------------------------------- |
---|
| 36 | ! Compute shortwave ice-particle scattering properties using Fu |
---|
| 37 | ! (1996) parameterization. The asymmetry factor in band 14 goes |
---|
| 38 | ! larger than one for re > 100.8 um, so we cap re at 100 um. |
---|
| 39 | ! Asymmetry factor is capped at just less than 1 because if it is |
---|
| 40 | ! exactly 1 then delta-Eddington scaling leads to a zero scattering |
---|
| 41 | ! optical depth and then division by zero. |
---|
| 42 | subroutine calc_ice_optics_fu_sw(nb, coeff, ice_wp, & |
---|
| 43 | & re, od, scat_od, g) |
---|
| 44 | |
---|
| 45 | !use yomhook, only : lhook, dr_hook |
---|
| 46 | |
---|
| 47 | ! Number of bands |
---|
| 48 | integer, intent(in) :: nb |
---|
| 49 | ! Coefficients read from a data file |
---|
| 50 | real(jprb), intent(in) :: coeff(:,:) |
---|
| 51 | ! Ice water path (kg m-2) |
---|
| 52 | real(jprb), intent(in) :: ice_wp |
---|
| 53 | ! Effective radius (m) |
---|
| 54 | real(jprb), intent(in) :: re |
---|
| 55 | ! Total optical depth, scattering optical depth and asymmetry factor |
---|
| 56 | real(jprb), intent(out) :: od(nb), scat_od(nb), g(nb) |
---|
| 57 | |
---|
| 58 | ! Fu's effective diameter (microns) and its inverse |
---|
| 59 | real(jprb) :: de_um, inv_de_um |
---|
| 60 | ! Ice water path in g m-2 |
---|
| 61 | real (jprb) :: iwp_gm_2 |
---|
| 62 | |
---|
| 63 | !real(jprb) :: hook_handle |
---|
| 64 | |
---|
| 65 | !if (lhook) call dr_hook('radiation_ice_optics:calc_ice_optics_fu_sw',0,hook_handle) |
---|
| 66 | |
---|
| 67 | ! Convert to effective diameter using the relationship in the IFS |
---|
| 68 | de_um = min(re, MaxEffectiveRadius) * (1.0e6_jprb / 0.64952_jprb) |
---|
| 69 | inv_de_um = 1.0_jprb / de_um |
---|
| 70 | iwp_gm_2 = ice_wp * 1000.0_jprb |
---|
| 71 | |
---|
| 72 | od = iwp_gm_2 * (coeff(1:nb,1) + coeff(1:nb,2) * inv_de_um) |
---|
| 73 | scat_od = od * (1.0_jprb - (coeff(1:nb,3) + de_um*(coeff(1:nb,4) & |
---|
| 74 | & + de_um*(coeff(1:nb,5) + de_um*coeff(1:nb,6))))) |
---|
| 75 | g = min(coeff(1:nb,7) + de_um*(coeff(1:nb,8) & |
---|
| 76 | & + de_um*(coeff(1:nb,9) + de_um*coeff(1:nb,10))), & |
---|
| 77 | & MaxAsymmetryFactor) |
---|
| 78 | |
---|
| 79 | !if (lhook) call dr_hook('radiation_ice_optics:calc_ice_optics_fu_sw',1,hook_handle) |
---|
| 80 | |
---|
| 81 | end subroutine calc_ice_optics_fu_sw |
---|
| 82 | |
---|
| 83 | |
---|
| 84 | !--------------------------------------------------------------------- |
---|
| 85 | ! Compute longwave ice-particle scattering properties using Fu et |
---|
| 86 | ! al. (1998) parameterization |
---|
| 87 | subroutine calc_ice_optics_fu_lw(nb, coeff, ice_wp, & |
---|
| 88 | & re, od, scat_od, g) |
---|
| 89 | |
---|
| 90 | !use yomhook, only : lhook, dr_hook |
---|
| 91 | |
---|
| 92 | ! Number of bands |
---|
| 93 | integer, intent(in) :: nb |
---|
| 94 | ! Coefficients read from a data file |
---|
| 95 | real(jprb), intent(in) :: coeff(:,:) |
---|
| 96 | ! Ice water path (kg m-2) |
---|
| 97 | real(jprb), intent(in) :: ice_wp |
---|
| 98 | ! Effective radius (m) |
---|
| 99 | real(jprb), intent(in) :: re |
---|
| 100 | ! Total optical depth, scattering optical depth and asymmetry factor |
---|
| 101 | real(jprb), intent(out) :: od(nb), scat_od(nb), g(nb) |
---|
| 102 | |
---|
| 103 | ! Fu's effective diameter (microns) and its inverse |
---|
| 104 | real(jprb) :: de_um, inv_de_um |
---|
| 105 | ! Ice water path in g m-2 |
---|
| 106 | real (jprb) :: iwp_gm_2 |
---|
| 107 | |
---|
| 108 | !real(jprb) :: hook_handle |
---|
| 109 | |
---|
| 110 | !if (lhook) call dr_hook('radiation_ice_optics:calc_ice_optics_fu_lw',0,hook_handle) |
---|
| 111 | |
---|
| 112 | ! Convert to effective diameter using the relationship in the IFS |
---|
| 113 | de_um = min(re, MaxEffectiveRadius) * (1.0e6_jprb / 0.64952_jprb) |
---|
| 114 | |
---|
| 115 | inv_de_um = 1.0_jprb / de_um |
---|
| 116 | iwp_gm_2 = ice_wp * 1000.0_jprb |
---|
| 117 | |
---|
| 118 | od = iwp_gm_2 * (coeff(1:nb,1) + inv_de_um*(coeff(1:nb,2) & |
---|
| 119 | & + inv_de_um*coeff(1:nb,3))) |
---|
| 120 | scat_od = od - iwp_gm_2*inv_de_um*(coeff(1:nb,4) + de_um*(coeff(1:nb,5) & |
---|
| 121 | & + de_um*(coeff(1:nb,6) + de_um*coeff(1:nb,7)))) |
---|
| 122 | g = min(coeff(1:nb,8) + de_um*(coeff(1:nb,9) & |
---|
| 123 | & + de_um*(coeff(1:nb,10) + de_um*coeff(1:nb,11))), & |
---|
| 124 | & MaxAsymmetryFactor) |
---|
| 125 | |
---|
| 126 | !if (lhook) call dr_hook('radiation_ice_optics:calc_ice_optics_fu_lw',1,hook_handle) |
---|
| 127 | |
---|
| 128 | end subroutine calc_ice_optics_fu_lw |
---|
| 129 | |
---|
| 130 | end module radiation_ice_optics_fu |
---|