! radiation_mcica_lw.F90 - Monte-Carlo Independent Column Approximation longtwave solver ! ! (C) Copyright 2015- ECMWF. ! ! This software is licensed under the terms of the Apache Licence Version 2.0 ! which can be obtained at http://www.apache.org/licenses/LICENSE-2.0. ! ! In applying this licence, ECMWF does not waive the privileges and immunities ! granted to it by virtue of its status as an intergovernmental organisation ! nor does it submit to any jurisdiction. ! ! Author: Robin Hogan ! Email: r.j.hogan@ecmwf.int ! ! Modifications ! 2017-04-11 R. Hogan Receive emission/albedo rather than planck/emissivity ! 2017-04-22 R. Hogan Store surface fluxes at all g-points ! 2017-07-12 R. Hogan Call fast adding method if only clouds scatter ! 2017-10-23 R. Hogan Renamed single-character variables module radiation_mcica_lw public contains !--------------------------------------------------------------------- ! Longwave Monte Carlo Independent Column Approximation ! (McICA). This implementation performs a clear-sky and a cloudy-sky ! calculation, and then weights the two to get the all-sky fluxes ! according to the total cloud cover. This method reduces noise for ! low cloud cover situations, and exploits the clear-sky ! calculations that are usually performed for diagnostic purposes ! simultaneously. The cloud generator has been carefully written ! such that the stochastic cloud field satisfies the prescribed ! overlap parameter accounting for this weighting. subroutine solver_mcica_lw(nlev,istartcol,iendcol, & & config, single_level, cloud, & & od, ssa, g, od_cloud, ssa_cloud, g_cloud, planck_hl, & & emission, albedo, & & flux) use parkind1, only : jprb use yomhook, only : lhook, dr_hook, jphook use radiation_io, only : nulerr, radiation_abort use radiation_config, only : config_type use radiation_single_level, only : single_level_type use radiation_cloud, only : cloud_type use radiation_flux, only : flux_type use radiation_two_stream, only : calc_ref_trans_lw, & & calc_no_scattering_transmittance_lw use radiation_adding_ica_lw, only : adding_ica_lw, fast_adding_ica_lw, & & calc_fluxes_no_scattering_lw use radiation_lw_derivatives, only : calc_lw_derivatives_ica, modify_lw_derivatives_ica use radiation_cloud_generator, only: cloud_generator implicit none ! Inputs integer, intent(in) :: nlev ! number of model levels integer, intent(in) :: istartcol, iendcol ! range of columns to process type(config_type), intent(in) :: config type(single_level_type), intent(in) :: single_level type(cloud_type), intent(in) :: cloud ! Gas and aerosol optical depth, single-scattering albedo and ! asymmetry factor at each longwave g-point real(jprb), intent(in), dimension(config%n_g_lw, nlev, istartcol:iendcol) :: & & od real(jprb), intent(in), dimension(config%n_g_lw_if_scattering, nlev, istartcol:iendcol) :: & & ssa, g ! Cloud and precipitation optical depth, single-scattering albedo and ! asymmetry factor in each longwave band real(jprb), intent(in), dimension(config%n_bands_lw,nlev,istartcol:iendcol) :: & & od_cloud real(jprb), intent(in), dimension(config%n_bands_lw_if_scattering, & & nlev,istartcol:iendcol) :: ssa_cloud, g_cloud ! Planck function at each half-level and the surface real(jprb), intent(in), dimension(config%n_g_lw,nlev+1,istartcol:iendcol) :: & & planck_hl ! Emission (Planck*emissivity) and albedo (1-emissivity) at the ! surface at each longwave g-point real(jprb), intent(in), dimension(config%n_g_lw, istartcol:iendcol) :: emission, albedo ! Output type(flux_type), intent(inout):: flux ! Local variables ! Diffuse reflectance and transmittance for each layer in clear ! and all skies real(jprb), dimension(config%n_g_lw, nlev) :: ref_clear, trans_clear, reflectance, transmittance ! Emission by a layer into the upwelling or downwelling diffuse ! streams, in clear and all skies real(jprb), dimension(config%n_g_lw, nlev) :: source_up_clear, source_dn_clear, source_up, source_dn ! Fluxes per g point real(jprb), dimension(config%n_g_lw, nlev+1) :: flux_up, flux_dn real(jprb), dimension(config%n_g_lw, nlev+1) :: flux_up_clear, flux_dn_clear ! Combined gas+aerosol+cloud optical depth, single scattering ! albedo and asymmetry factor real(jprb), dimension(config%n_g_lw) :: od_total, ssa_total, g_total ! Combined scattering optical depth real(jprb) :: scat_od, scat_od_total(config%n_g_lw) ! Optical depth scaling from the cloud generator, zero indicating ! clear skies real(jprb), dimension(config%n_g_lw,nlev) :: od_scaling ! Modified optical depth after McICA scaling to represent cloud ! inhomogeneity real(jprb), dimension(config%n_g_lw) :: od_cloud_new ! Total cloud cover output from the cloud generator real(jprb) :: total_cloud_cover ! Identify clear-sky layers logical :: is_clear_sky_layer(nlev) ! Index of the highest cloudy layer integer :: i_cloud_top ! Number of g points integer :: ng ! Loop indices for level, column and g point integer :: jlev, jcol, jg real(jphook) :: hook_handle if (lhook) call dr_hook('radiation_mcica_lw:solver_mcica_lw',0,hook_handle) if (.not. config%do_clear) then write(nulerr,'(a)') '*** Error: longwave McICA requires clear-sky calculation to be performed' call radiation_abort() end if ng = config%n_g_lw ! Loop through columns do jcol = istartcol,iendcol ! Clear-sky calculation if (config%do_lw_aerosol_scattering) then ! Scattering case: first compute clear-sky reflectance, ! transmittance etc at each model level call calc_ref_trans_lw(ng*nlev, & & od(:,:,jcol), ssa(:,:,jcol), g(:,:,jcol), & & planck_hl(:,1:nlev,jcol), planck_hl(:,2:nlev+1,jcol), & & ref_clear, trans_clear, & & source_up_clear, source_dn_clear) ! Then use adding method to compute fluxes call adding_ica_lw(ng, nlev, & & ref_clear, trans_clear, source_up_clear, source_dn_clear, & & emission(:,jcol), albedo(:,jcol), & & flux_up_clear, flux_dn_clear) else ! Non-scattering case: use simpler functions for ! transmission and emission call calc_no_scattering_transmittance_lw(ng*nlev, od(:,:,jcol), & & planck_hl(:,1:nlev,jcol), planck_hl(:,2:nlev+1, jcol), & & trans_clear, source_up_clear, source_dn_clear) ! Ensure that clear-sky reflectance is zero since it may be ! used in cloudy-sky case ref_clear = 0.0_jprb ! Simpler down-then-up method to compute fluxes call calc_fluxes_no_scattering_lw(ng, nlev, & & trans_clear, source_up_clear, source_dn_clear, & & emission(:,jcol), albedo(:,jcol), & & flux_up_clear, flux_dn_clear) end if ! Sum over g-points to compute broadband fluxes flux%lw_up_clear(jcol,:) = sum(flux_up_clear,1) flux%lw_dn_clear(jcol,:) = sum(flux_dn_clear,1) ! Store surface spectral downwelling fluxes flux%lw_dn_surf_clear_g(:,jcol) = flux_dn_clear(:,nlev+1) ! Do cloudy-sky calculation; add a prime number to the seed in ! the longwave call cloud_generator(ng, nlev, config%i_overlap_scheme, & & single_level%iseed(jcol) + 997, & & config%cloud_fraction_threshold, & & cloud%fraction(jcol,:), cloud%overlap_param(jcol,:), & & config%cloud_inhom_decorr_scaling, cloud%fractional_std(jcol,:), & & config%pdf_sampler, od_scaling, total_cloud_cover, & & use_beta_overlap=config%use_beta_overlap, & & use_vectorizable_generator=config%use_vectorizable_generator) ! Store total cloud cover flux%cloud_cover_lw(jcol) = total_cloud_cover if (total_cloud_cover >= config%cloud_fraction_threshold) then ! Total-sky calculation is_clear_sky_layer = .true. i_cloud_top = nlev+1 do jlev = 1,nlev ! Compute combined gas+aerosol+cloud optical properties if (cloud%fraction(jcol,jlev) >= config%cloud_fraction_threshold) then is_clear_sky_layer(jlev) = .false. ! Get index to the first cloudy layer from the top if (i_cloud_top > jlev) then i_cloud_top = jlev end if do jg = 1,ng od_cloud_new(jg) = od_scaling(jg,jlev) & & * od_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) od_total(jg) = od(jg,jlev,jcol) + od_cloud_new(jg) ssa_total(jg) = 0.0_jprb g_total(jg) = 0.0_jprb end do if (config%do_lw_cloud_scattering) then ! Scattering case: calculate reflectance and ! transmittance at each model level if (config%do_lw_aerosol_scattering) then ! In single precision we need to protect against the ! case that od_total > 0.0 and ssa_total > 0.0 but ! od_total*ssa_total == 0 due to underflow do jg = 1,ng if (od_total(jg) > 0.0_jprb) then scat_od_total(jg) = ssa(jg,jlev,jcol)*od(jg,jlev,jcol) & & + ssa_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & & * od_cloud_new(jg) ssa_total(jg) = scat_od_total(jg) / od_total(jg) if (scat_od_total(jg) > 0.0_jprb) then g_total(jg) = (g(jg,jlev,jcol)*ssa(jg,jlev,jcol)*od(jg,jlev,jcol) & & + g_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & & * ssa_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & & * od_cloud_new(jg)) & & / scat_od_total(jg) end if end if end do else do jg = 1,ng if (od_total(jg) > 0.0_jprb) then scat_od = ssa_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & & * od_cloud_new(jg) ssa_total(jg) = scat_od / od_total(jg) if (scat_od > 0.0_jprb) then g_total(jg) = g_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & & * ssa_cloud(config%i_band_from_reordered_g_lw(jg),jlev,jcol) & & * od_cloud_new(jg) / scat_od end if end if end do end if ! Compute cloudy-sky reflectance, transmittance etc at ! each model level call calc_ref_trans_lw(ng, & & od_total, ssa_total, g_total, & & planck_hl(:,jlev,jcol), planck_hl(:,jlev+1,jcol), & & reflectance(:,jlev), transmittance(:,jlev), & & source_up(:,jlev), source_dn(:,jlev)) else ! No-scattering case: use simpler functions for ! transmission and emission call calc_no_scattering_transmittance_lw(ng, od_total, & & planck_hl(:,jlev,jcol), planck_hl(:,jlev+1, jcol), & & transmittance(:,jlev), source_up(:,jlev), source_dn(:,jlev)) end if else ! Clear-sky layer: copy over clear-sky values reflectance(:,jlev) = ref_clear(:,jlev) transmittance(:,jlev) = trans_clear(:,jlev) source_up(:,jlev) = source_up_clear(:,jlev) source_dn(:,jlev) = source_dn_clear(:,jlev) end if end do if (config%do_lw_aerosol_scattering) then ! Use adding method to compute fluxes for an overcast sky, ! allowing for scattering in all layers call adding_ica_lw(ng, nlev, reflectance, transmittance, source_up, source_dn, & & emission(:,jcol), albedo(:,jcol), & & flux_up, flux_dn) else if (config%do_lw_cloud_scattering) then ! Use adding method to compute fluxes but optimize for the ! presence of clear-sky layers call fast_adding_ica_lw(ng, nlev, reflectance, transmittance, source_up, source_dn, & & emission(:,jcol), albedo(:,jcol), & & is_clear_sky_layer, i_cloud_top, flux_dn_clear, & & flux_up, flux_dn) else ! Simpler down-then-up method to compute fluxes call calc_fluxes_no_scattering_lw(ng, nlev, & & transmittance, source_up, source_dn, emission(:,jcol), albedo(:,jcol), & & flux_up, flux_dn) end if ! Store overcast broadband fluxes flux%lw_up(jcol,:) = sum(flux_up,1) flux%lw_dn(jcol,:) = sum(flux_dn,1) ! Cloudy flux profiles currently assume completely overcast ! skies; perform weighted average with clear-sky profile flux%lw_up(jcol,:) = total_cloud_cover *flux%lw_up(jcol,:) & & + (1.0_jprb - total_cloud_cover)*flux%lw_up_clear(jcol,:) flux%lw_dn(jcol,:) = total_cloud_cover *flux%lw_dn(jcol,:) & & + (1.0_jprb - total_cloud_cover)*flux%lw_dn_clear(jcol,:) ! Store surface spectral downwelling fluxes flux%lw_dn_surf_g(:,jcol) = total_cloud_cover*flux_dn(:,nlev+1) & & + (1.0_jprb - total_cloud_cover)*flux%lw_dn_surf_clear_g(:,jcol) ! Compute the longwave derivatives needed by Hogan and Bozzo ! (2015) approximate radiation update scheme if (config%do_lw_derivatives) then call calc_lw_derivatives_ica(ng, nlev, jcol, transmittance, flux_up(:,nlev+1), & & flux%lw_derivatives) if (total_cloud_cover < 1.0_jprb - config%cloud_fraction_threshold) then ! Modify the existing derivative with the contribution from the clear sky call modify_lw_derivatives_ica(ng, nlev, jcol, trans_clear, flux_up_clear(:,nlev+1), & & 1.0_jprb-total_cloud_cover, flux%lw_derivatives) end if end if else ! No cloud in profile and clear-sky fluxes already ! calculated: copy them over flux%lw_up(jcol,:) = flux%lw_up_clear(jcol,:) flux%lw_dn(jcol,:) = flux%lw_dn_clear(jcol,:) flux%lw_dn_surf_g(:,jcol) = flux%lw_dn_surf_clear_g(:,jcol) if (config%do_lw_derivatives) then call calc_lw_derivatives_ica(ng, nlev, jcol, trans_clear, flux_up_clear(:,nlev+1), & & flux%lw_derivatives) end if end if ! Cloud is present in profile end do if (lhook) call dr_hook('radiation_mcica_lw:solver_mcica_lw',1,hook_handle) end subroutine solver_mcica_lw end module radiation_mcica_lw