[3880] | 1 | ! radiation_delta_eddington.h - Delta-Eddington scaling |
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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 | ! This file is intended to be included inside a module to ensure that |
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| 16 | ! these simple functions may be inlined |
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| 17 | |
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| 18 | !--------------------------------------------------------------------- |
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| 19 | ! Perform in-place delta-Eddington scaling of the phase function |
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| 20 | elemental subroutine delta_eddington(od, ssa, g) |
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| 21 | |
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| 22 | use parkind1, only : jprb |
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| 23 | |
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| 24 | ! Total optical depth, single scattering albedo and asymmetry |
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| 25 | ! factor |
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| 26 | real(jprb), intent(inout) :: od, ssa, g |
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| 27 | |
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| 28 | ! Fraction of the phase function deemed to be in the forward lobe |
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| 29 | ! and therefore treated as if it is not scattered at all |
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| 30 | real(jprb) :: f |
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| 31 | |
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| 32 | f = g*g |
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| 33 | od = od * (1.0_jprb - ssa*f) |
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| 34 | ssa = ssa * (1.0_jprb - f) / (1.0_jprb - ssa*f) |
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| 35 | g = g / (1.0_jprb + g) |
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| 36 | |
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| 37 | end subroutine delta_eddington |
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| 38 | |
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| 39 | |
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| 40 | !--------------------------------------------------------------------- |
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| 41 | ! Perform in-place delta-Eddington scaling of the phase function, but |
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| 42 | ! using extensive variables (i.e. the scattering optical depth, |
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| 43 | ! scat_od, rather than the single-scattering albedo, and the |
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| 44 | ! scattering-optical-depth-multiplied-by-asymmetry-factor, scat_od_g, |
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| 45 | ! rather than the asymmetry factor. |
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| 46 | elemental subroutine delta_eddington_extensive(od, scat_od, scat_od_g) |
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| 47 | |
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| 48 | use parkind1, only : jprb |
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| 49 | |
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| 50 | ! Total optical depth, scattering optical depth and asymmetry factor |
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| 51 | ! multiplied by the scattering optical depth |
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| 52 | real(jprb), intent(inout) :: od, scat_od, scat_od_g |
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| 53 | |
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| 54 | ! Fraction of the phase function deemed to be in the forward lobe |
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| 55 | ! and therefore treated as if it is not scattered at all |
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| 56 | real(jprb) :: f, g |
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| 57 | |
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| 58 | if (scat_od > 0.0_jprb) then |
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| 59 | g = scat_od_g / scat_od |
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| 60 | else |
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| 61 | g = 0.0 |
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| 62 | end if |
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| 63 | |
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| 64 | f = g*g |
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| 65 | od = od - scat_od * f |
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| 66 | scat_od = scat_od * (1.0_jprb - f) |
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| 67 | scat_od_g = scat_od * g / (1.0_jprb + g) |
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| 68 | |
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| 69 | end subroutine delta_eddington_extensive |
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| 70 | |
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| 71 | |
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| 72 | !--------------------------------------------------------------------- |
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| 73 | ! Perform in-place delta-Eddington scaling of the phase function, |
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| 74 | ! using the scattering optical depth rather than the single scattering |
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| 75 | ! albedo |
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| 76 | elemental subroutine delta_eddington_scat_od(od, scat_od, g) |
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| 77 | |
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| 78 | use parkind1, only : jprb |
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| 79 | |
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| 80 | ! Total optical depth, scattering optical depth and asymmetry factor |
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| 81 | real(jprb), intent(inout) :: od, scat_od, g |
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| 82 | |
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| 83 | ! Fraction of the phase function deemed to be in the forward lobe |
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| 84 | ! and therefore treated as if it is not scattered at all |
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| 85 | real(jprb) :: f |
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| 86 | |
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| 87 | f = g*g |
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| 88 | od = od - scat_od * f |
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| 89 | scat_od = scat_od * (1.0_jprb - f) |
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| 90 | g = g / (1.0_jprb + g) |
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| 91 | |
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| 92 | end subroutine delta_eddington_scat_od |
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| 93 | |
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