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surf_landice_mod.F90

Last change on this file was 4947, checked in by evignon, 6 weeks ago
ajout de la parameterisation de rugosite de la neige sur les calottes de Amory et al. 2017
Property copyright set to Name of program: LMDZ Creation date: 1984 Version: LMDZ5 License: CeCILL version 2 Holder: Laboratoire de m\'et\'eorologie dynamique, CNRS, UMR 8539 See the license file in the root directory Property svn:eol-style set to `native` Property svn:keywords set to `Author Date Id Revision`
File size: 24.3 KB

Rev	Line
[781]	1	!
	2	MODULE surf_landice_mod
	3
	4	IMPLICIT NONE
	5
	6	CONTAINS
	7	!
	8	!****************************************************************************************
	9	!
	10	SUBROUTINE surf_landice(itime, dtime, knon, knindex, &
[1865]	11	rlon, rlat, debut, lafin, &
	12	rmu0, lwdownm, albedo, pphi1, &
[888]	13	swnet, lwnet, tsurf, p1lay, &
[4523]	14	cdragh, cdragm, precip_rain, precip_snow, precip_bs, temp_air, spechum, &
[1067]	15	AcoefH, AcoefQ, BcoefH, BcoefQ, &
	16	AcoefU, AcoefV, BcoefU, BcoefV, &
[4529]	17	AcoefQBS, BcoefQBS, &
[2240]	18	ps, u1, v1, gustiness, rugoro, pctsrf, &
[4523]	19	snow, qsurf, qsol, qbs1, agesno, &
	20	tsoil, z0m, z0h, SFRWL, alb_dir, alb_dif, evap, fluxsens, fluxlat, fluxbs, &
[1067]	21	tsurf_new, dflux_s, dflux_l, &
[3900]	22	alt, slope, cloudf, &
[1865]	23	snowhgt, qsnow, to_ice, sissnow, &
	24	alb3, runoff, &
[1067]	25	flux_u1, flux_v1)
[781]	26
[1067]	27	USE dimphy
[3974]	28	USE geometry_mod, ONLY : longitude,latitude
[3900]	29	USE surface_data, ONLY : type_ocean, calice, calsno, landice_opt, iflag_albcalc
	30	USE fonte_neige_mod, ONLY : fonte_neige,run_off_lic,fqcalving_global,ffonte_global,fqfonte_global,runofflic_global
[1067]	31	USE cpl_mod, ONLY : cpl_send_landice_fields
	32	USE calcul_fluxs_mod
[4835]	33	USE phys_local_var_mod, ONLY : zxrhoslic, zxustartlic, zxqsaltlic
[4414]	34	USE phys_output_var_mod, ONLY : snow_o,zfra_o
[2728]	35	!FC
	36	USE ioipsl_getin_p_mod, ONLY : getin_p
[4835]	37	USE lmdz_blowing_snow_ini, ONLY : c_esalt_bs, zeta_bs, pbst_bs, prt_bs, rhoice_bs, rhohard_bs
	38	USE lmdz_blowing_snow_ini, ONLY : rhofresh_bs, tau_eqsalt_bs, tau_dens0_bs, tau_densmin_bs
[3792]	39	#ifdef CPP_INLANDSIS
	40	USE surf_inlandsis_mod, ONLY : surf_inlandsis
	41	#endif
	42
[1785]	43	USE indice_sol_mod
[1067]	44
[1785]	45	! INCLUDE "indicesol.h"
[781]	46	INCLUDE "dimsoil.h"
[793]	47	INCLUDE "YOMCST.h"
	48	INCLUDE "clesphys.h"
[781]	49
	50	! Input variables
	51	!****************************************************************************************
	52	INTEGER, INTENT(IN) :: itime, knon
	53	INTEGER, DIMENSION(klon), INTENT(in) :: knindex
	54	REAL, INTENT(in) :: dtime
[888]	55	REAL, DIMENSION(klon), INTENT(IN) :: swnet ! net shortwave radiance
	56	REAL, DIMENSION(klon), INTENT(IN) :: lwnet ! net longwave radiance
[781]	57	REAL, DIMENSION(klon), INTENT(IN) :: tsurf
	58	REAL, DIMENSION(klon), INTENT(IN) :: p1lay
[1067]	59	REAL, DIMENSION(klon), INTENT(IN) :: cdragh, cdragm
[4523]	60	REAL, DIMENSION(klon), INTENT(IN) :: precip_rain, precip_snow, precip_bs
[781]	61	REAL, DIMENSION(klon), INTENT(IN) :: temp_air, spechum
[1067]	62	REAL, DIMENSION(klon), INTENT(IN) :: AcoefH, AcoefQ
	63	REAL, DIMENSION(klon), INTENT(IN) :: BcoefH, BcoefQ
	64	REAL, DIMENSION(klon), INTENT(IN) :: AcoefU, AcoefV, BcoefU, BcoefV
[4529]	65	REAL, DIMENSION(klon), INTENT(IN) :: AcoefQBS, BcoefQBS
[781]	66	REAL, DIMENSION(klon), INTENT(IN) :: ps
[4523]	67	REAL, DIMENSION(klon), INTENT(IN) :: u1, v1, gustiness, qbs1
[781]	68	REAL, DIMENSION(klon), INTENT(IN) :: rugoro
	69	REAL, DIMENSION(klon,nbsrf), INTENT(IN) :: pctsrf
	70
[1865]	71	LOGICAL, INTENT(IN) :: debut !true if first step
	72	LOGICAL, INTENT(IN) :: lafin !true if last step
	73	REAL, DIMENSION(klon), INTENT(IN) :: rlon, rlat
	74	REAL, DIMENSION(klon), INTENT(IN) :: rmu0
	75	REAL, DIMENSION(klon), INTENT(IN) :: lwdownm !ylwdown
	76	REAL, DIMENSION(klon), INTENT(IN) :: albedo !mean albedo
	77	REAL, DIMENSION(klon), INTENT(IN) :: pphi1
[3900]	78	REAL, DIMENSION(klon), INTENT(IN) :: alt !mean altitude of the grid box
[1865]	79	REAL, DIMENSION(klon), INTENT(IN) :: slope !mean slope in grid box
	80	REAL, DIMENSION(klon), INTENT(IN) :: cloudf !total cloud fraction
	81
[781]	82	! In/Output variables
	83	!****************************************************************************************
	84	REAL, DIMENSION(klon), INTENT(INOUT) :: snow, qsol
	85	REAL, DIMENSION(klon), INTENT(INOUT) :: agesno
	86	REAL, DIMENSION(klon, nsoilmx), INTENT(INOUT) :: tsoil
	87
	88	! Output variables
	89	!****************************************************************************************
	90	REAL, DIMENSION(klon), INTENT(OUT) :: qsurf
[2243]	91	REAL, DIMENSION(klon), INTENT(OUT) :: z0m, z0h
[2227]	92	!albedo SB >>>
	93	! REAL, DIMENSION(klon), INTENT(OUT) :: alb1 ! new albedo in visible SW interval
	94	! REAL, DIMENSION(klon), INTENT(OUT) :: alb2 ! new albedo in near IR interval
[3792]	95	REAL, DIMENSION(6), INTENT(IN) :: SFRWL
	96	REAL, DIMENSION(klon,nsw), INTENT(OUT) :: alb_dir,alb_dif
[2227]	97	!albedo SB <<<
[781]	98	REAL, DIMENSION(klon), INTENT(OUT) :: evap, fluxsens, fluxlat
[4523]	99	REAL, DIMENSION(klon), INTENT(OUT) :: fluxbs
[888]	100	REAL, DIMENSION(klon), INTENT(OUT) :: tsurf_new
[781]	101	REAL, DIMENSION(klon), INTENT(OUT) :: dflux_s, dflux_l
[1067]	102	REAL, DIMENSION(klon), INTENT(OUT) :: flux_u1, flux_v1
[781]	103
[1865]	104	REAL, DIMENSION(klon), INTENT(OUT) :: alb3
	105	REAL, DIMENSION(klon), INTENT(OUT) :: qsnow !column water in snow [kg/m2]
	106	REAL, DIMENSION(klon), INTENT(OUT) :: snowhgt !Snow height (m)
	107	REAL, DIMENSION(klon), INTENT(OUT) :: to_ice
	108	REAL, DIMENSION(klon), INTENT(OUT) :: sissnow
	109	REAL, DIMENSION(klon), INTENT(OUT) :: runoff !Land ice runoff
	110
	111
[781]	112	! Local variables
	113	!****************************************************************************************
	114	REAL, DIMENSION(klon) :: soilcap, soilflux
	115	REAL, DIMENSION(klon) :: cal, beta, dif_grnd
	116	REAL, DIMENSION(klon) :: zfra, alb_neig
[888]	117	REAL, DIMENSION(klon) :: radsol
[3792]	118	REAL, DIMENSION(klon) :: u0, v0, u1_lay, v1_lay, ustar
	119	INTEGER :: i,j,nt
[3900]	120	REAL, DIMENSION(klon) :: fqfonte,ffonte
[4283]	121	REAL, DIMENSION(klon) :: run_off_lic_frac
[1865]	122	REAL, DIMENSION(klon) :: emis_new !Emissivity
	123	REAL, DIMENSION(klon) :: swdown,lwdown
[3900]	124	REAL, DIMENSION(klon) :: precip_snow_adv, snow_adv !Snow Drift precip./advection (not used in inlandsis)
	125	REAL, DIMENSION(klon) :: erod !erosion of surface snow (flux, kg/m2/s like evap)
	126	REAL, DIMENSION(klon) :: zsl_height, wind_velo !surface layer height, wind spd
[1865]	127	REAL, DIMENSION(klon) :: dens_air, snow_cont_air !air density; snow content air
	128	REAL, DIMENSION(klon) :: alb_soil !albedo of underlying ice
	129	REAL, DIMENSION(klon) :: pexner !Exner potential
	130	REAL :: pref
[3792]	131	REAL, DIMENSION(klon,nsoilmx) :: tsoil0 !modif
	132	REAL :: dtis ! subtimestep
	133	LOGICAL :: debut_is, lafin_is ! debut and lafin for inlandsis
[1865]	134
	135	CHARACTER (len = 20) :: modname = 'surf_landice'
	136	CHARACTER (len = 80) :: abort_message
	137
[2728]	138
[3900]	139	REAL,DIMENSION(klon) :: alb1,alb2
[4523]	140	REAL,DIMENSION(klon) :: precip_totsnow, evap_totsnow
[3900]	141	REAL, DIMENSION (klon,6) :: alb6
[4835]	142	REAL :: esalt
[4529]	143	REAL :: lambdasalt,fluxsalt, csalt, nunu, aa, bb, cc
[4916]	144	REAL :: tau_dens, maxerosion
[4835]	145	REAL, DIMENSION(klon) :: ws1, rhod, rhos, ustart0, ustart, qsalt, hsalt
[4916]	146	REAL, DIMENSION(klon) :: fluxbs_1, fluxbs_2, bsweight_fresh
	147	LOGICAL, DIMENSION(klon) :: ok_remaining_freshsnow
[4947]	148	REAL :: ta1, ta2, ta3, z01, z02, z03, coefa, coefb, coefc, coefd
[4672]	149
[4947]	150
[781]	151	! End definition
	152	!****************************************************************************************
[2728]	153	!FC
	154	!FC
	155	REAL,SAVE :: alb_vis_sno_lic
	156	!$OMP THREADPRIVATE(alb_vis_sno_lic)
	157	REAL,SAVE :: alb_nir_sno_lic
	158	!$OMP THREADPRIVATE(alb_nir_sno_lic)
	159	LOGICAL, SAVE :: firstcall = .TRUE.
	160	!$OMP THREADPRIVATE(firstcall)
	161
	162
[3792]	163	!FC firtscall initializations
	164	!******************************************************************************************
[2728]	165	IF (firstcall) THEN
	166	alb_vis_sno_lic=0.77
	167	CALL getin_p('alb_vis_sno_lic',alb_vis_sno_lic)
	168	PRINT*, 'alb_vis_sno_lic',alb_vis_sno_lic
	169	alb_nir_sno_lic=0.77
	170	CALL getin_p('alb_nir_sno_lic',alb_nir_sno_lic)
	171	PRINT*, 'alb_nir_sno_lic',alb_nir_sno_lic
[3792]	172
[2728]	173	firstcall=.false.
	174	ENDIF
[3792]	175	!******************************************************************************************
	176
[781]	177	! Initialize output variables
[1865]	178	alb3(:) = 999999.
[888]	179	alb2(:) = 999999.
	180	alb1(:) = 999999.
[4523]	181	fluxbs(:)=0.
[1865]	182	runoff(:) = 0.
[888]	183	!****************************************************************************************
	184	! Calculate total absorbed radiance at surface
	185	!
	186	!****************************************************************************************
	187	radsol(:) = 0.0
	188	radsol(1:knon) = swnet(1:knon) + lwnet(1:knon)
[781]	189
	190	!****************************************************************************************
[4523]	191
	192	!****************************************************************************************
[3792]	193	! landice_opt = 0 : soil_model, calcul_flux, fonte_neige, ...
[3901]	194	! landice_opt = 1 : prepare and call INterace Lmdz SISvat (INLANDSIS)
[1865]	195	!****************************************************************************************
[3792]	196
	197
	198	IF (landice_opt .EQ. 1) THEN
	199
[3901]	200	!****************************************************************************************
[3792]	201	! CALL to INLANDSIS interface
	202	!****************************************************************************************
	203	#ifdef CPP_INLANDSIS
	204
	205	debut_is=debut
	206	lafin_is=.false.
	207	! Suppose zero surface speed
	208	u0(:) = 0.0
	209	v0(:) = 0.0
	210
	211
	212	CALL calcul_flux_wind(knon, dtime, &
	213	u0, v0, u1, v1, gustiness, cdragm, &
	214	AcoefU, AcoefV, BcoefU, BcoefV, &
	215	p1lay, temp_air, &
	216	flux_u1, flux_v1)
	217
	218
	219	! Set constants and compute some input for SISVAT
	220	! = 1000 hPa
	221	! and calculate incoming flux for SW and LW interval: swdown, lwdown
	222	swdown(:) = 0.0
	223	lwdown(:) = 0.0
[3900]	224	snow_cont_air(:) = 0. ! the snow content in air is not a prognostic variable of the model
[3792]	225	alb_soil(:) = 0.4 ! before albedo(:) but here it is the ice albedo that we have to set
	226	ustar(:) = 0.
	227	pref = 100000.
	228	DO i = 1, knon
	229	swdown(i) = swnet(i)/(1-albedo(i))
	230	lwdown(i) = lwdownm(i)
	231	wind_velo(i) = u1(i)2 + v1(i)2
	232	wind_velo(i) = wind_velo(i)**0.5
	233	pexner(i) = (p1lay(i)/pref)**(RD/RCPD)
	234	dens_air(i) = p1lay(i)/RD/temp_air(i) ! dry air density
	235	zsl_height(i) = pphi1(i)/RG
	236	tsoil0(i,:) = tsoil(i,:)
	237	ustar(i)= (cdragm(i)(wind_velo(i)2))*0.5
	238	END DO
	239
	240
	241
[3900]	242	dtis=dtime
[3792]	243
[3900]	244	IF (lafin) THEN
[3792]	245	lafin_is=.true.
	246	END IF
	247
[3900]	248	CALL surf_inlandsis(knon, rlon, rlat, knindex, itime, dtis, debut_is, lafin_is,&
	249	rmu0, swdown, lwdown, albedo, pexner, ps, p1lay, precip_rain, precip_snow, &
	250	zsl_height, wind_velo, ustar, temp_air, dens_air, spechum, tsurf,&
	251	rugoro, snow_cont_air, alb_soil, alt, slope, cloudf, &
	252	radsol, qsol, tsoil0, snow, zfra, snowhgt, qsnow, to_ice, sissnow,agesno, &
[3792]	253	AcoefH, AcoefQ, BcoefH, BcoefQ, cdragm, cdragh, &
[3900]	254	run_off_lic, fqfonte, ffonte, evap, erod, fluxsens, fluxlat,dflux_s, dflux_l, &
	255	tsurf_new, alb1, alb2, alb3, alb6, &
	256	emis_new, z0m, z0h, qsurf)
[3792]	257
[3900]	258	debut_is=.false.
[3792]	259
	260
[3900]	261	! Treatment of snow melting and calving
[3792]	262
[3900]	263	! for consistency with standard LMDZ, add calving to run_off_lic
	264	run_off_lic(:)=run_off_lic(:) + to_ice(:)
	265
	266	DO i = 1, knon
	267	ffonte_global(knindex(i),is_lic) = ffonte(i)
	268	fqfonte_global(knindex(i),is_lic) = fqfonte(i)! net melting= melting - refreezing
	269	fqcalving_global(knindex(i),is_lic) = to_ice(i) ! flux
	270	runofflic_global(knindex(i)) = run_off_lic(i)
	271	ENDDO
	272	! Here, we assume that the calving term is equal to the to_ice term
	273	! (no ice accumulation)
	274
	275
[3792]	276	#else
[3901]	277	abort_message='Pb de coherence: landice_opt = 1 mais CPP_INLANDSIS = .false.'
[3792]	278	CALL abort_physic(modname,abort_message,1)
	279	#endif
	280
	281
	282	ELSE
	283
	284	!****************************************************************************************
[781]	285	! Soil calculations
	286	!
	287	!****************************************************************************************
[3780]	288
	289	! EV: use calbeta
	290	CALL calbeta(dtime, is_lic, knon, snow, qsol, beta, cal, dif_grnd)
	291
	292
	293	! use soil model and recalculate properly cal
[781]	294	IF (soil_model) THEN
[3974]	295	CALL soil(dtime, is_lic, knon, snow, tsurf, qsol, &
	296	& longitude(knindex(1:knon)), latitude(knindex(1:knon)), tsoil, soilcap, soilflux)
[781]	297	cal(1:knon) = RCPD / soilcap(1:knon)
	298	radsol(1:knon) = radsol(1:knon) + soilflux(1:knon)
	299	ELSE
	300	cal = RCPD * calice
	301	WHERE (snow > 0.0) cal = RCPD * calsno
	302	ENDIF
	303
	304
	305	!****************************************************************************************
	306	! Calulate fluxes
	307	!
	308	!****************************************************************************************
[3792]	309	! beta(:) = 1.0
	310	! dif_grnd(:) = 0.0
[781]	311
[1067]	312	! Suppose zero surface speed
	313	u0(:)=0.0
	314	v0(:)=0.0
	315	u1_lay(:) = u1(:) - u0(:)
	316	v1_lay(:) = v1(:) - v0(:)
	317
[781]	318	CALL calcul_fluxs(knon, is_lic, dtime, &
[2254]	319	tsurf, p1lay, cal, beta, cdragh, cdragh, ps, &
[781]	320	precip_rain, precip_snow, snow, qsurf, &
[2240]	321	radsol, dif_grnd, temp_air, spechum, u1_lay, v1_lay, gustiness, &
[2254]	322	1.,AcoefH, AcoefQ, BcoefH, BcoefQ, &
[781]	323	tsurf_new, evap, fluxlat, fluxsens, dflux_s, dflux_l)
	324
[1067]	325	CALL calcul_flux_wind(knon, dtime, &
[2240]	326	u0, v0, u1, v1, gustiness, cdragm, &
[1067]	327	AcoefU, AcoefV, BcoefU, BcoefV, &
	328	p1lay, temp_air, &
	329	flux_u1, flux_v1)
[781]	330
	331
	332	!****************************************************************************************
	333	! Calculate albedo
	334	!
	335	!****************************************************************************************
[3780]	336
[781]	337	!
	338	!IM: plusieurs choix/tests sur l'albedo des "glaciers continentaux"
[888]	339	! alb1(1 : knon) = 0.6 !IM cf FH/GK
	340	! alb1(1 : knon) = 0.82
	341	! alb1(1 : knon) = 0.77 !211003 Ksta0.77
	342	! alb1(1 : knon) = 0.8 !KstaTER0.8 & LMD_ARMIP5
[781]	343	!IM: KstaTER0.77 & LMD_ARMIP6
	344
[3780]	345	! Attantion: alb1 and alb2 are not the same!
[2728]	346	alb1(1:knon) = alb_vis_sno_lic
	347	alb2(1:knon) = alb_nir_sno_lic
[781]	348
	349
	350	!****************************************************************************************
	351	! Rugosity
	352	!
	353	!****************************************************************************************
[2243]	354
[4947]	355	if (z0m_landice .GT. 0.) then
	356	z0m(1:knon) = z0m_landice
	357	z0h(1:knon) = z0h_landice
	358	else
	359	! parameterization of z0=f(T) following measurements in Adelie Land by Amory et al 2018
	360	coefa = 0.1658 !0.1862 !Ant
	361	coefb = -50.3869 !-55.7718 !Ant
	362	ta1 = 253.15 !255. Ant
	363	ta2 = 273.15
	364	ta3 = 273.15+3
	365	z01 = exp(coefa*ta1 + coefb) !~0.2 ! ~0.25 mm
	366	z02 = exp(coefa*ta2 + coefb) !~6 !~7 mm
	367	z03 = z01
	368	coefc = log(z03/z02)/(ta3-ta2)
	369	coefd = log(z03)-coefc*ta3
	370	do j=1,knon
	371	if (temp_air(j) .lt. ta1) then
	372	z0m(j) = z01
	373	else if (temp_air(j).ge.ta1 .and. temp_air(j).lt.ta2) then
	374	z0m(j) = exp(coefa*temp_air(j) + coefb)
	375	else if (temp_air(j).ge.ta2 .and. temp_air(j).lt.ta3) then
	376	! if st > 0, melting induce smooth surface
	377	z0m(j) = exp(coefc*temp_air(j) + coefd)
	378	else
	379	z0m(j) = z03
	380	endif
	381	z0h(j)=z0m(j)
	382	enddo
[781]	383
[4947]	384	endif
	385
	386
[4835]	387	!****************************************************************************************
	388	! Simple blowing snow param
	389	!****************************************************************************************
	390	! we proceed in 2 steps:
	391	! first we erode - if possible -the accumulated snow during the time step
	392	! then we update the density of the underlying layer and see if we can also erode
	393	! this layer
[1865]	394
[4529]	395
[4835]	396	if (ok_bs) then
	397	fluxbs(:)=0.
[4947]	398	do j=1,knon
[4835]	399	ws1(j)=(u1(j)2+v1(j)2)**0.5
	400	ustar(j)=(cdragm(j)(u1(j)2+v1(j)2))*0.5
	401	rhod(j)=p1lay(j)/RD/temp_air(j)
	402	ustart0(j) =(log(2.868)-log(1.625))/0.085*sqrt(cdragm(j))
	403	enddo
	404
	405	! 1st step: erosion of fresh snow accumulated during the time step
	406	do j=1, knon
[4916]	407	if (precip_snow(j) .GT. 0.) then
[4835]	408	rhos(j)=rhofresh_bs
	409	! blowing snow flux formula used in MAR
	410	ustart(j)=ustart0(j)exp(max(rhoice_bs/rhofresh_bs-rhoice_bs/rhos(j),0.))exp(max(0.,rhos(j)-rhohard_bs))
	411	! we have multiplied by exp to prevent erosion when rhos>rhohard_bs
	412	! computation of qbs at the top of the saltation layer
	413	! default formulation from MAR model (Amory et al. 2021, Gallee et al. 2001)
	414	esalt=1./(c_esalt_bs*max(1.e-6,ustar(j)))
	415	hsalt(j)=0.08436(max(1.e-6,ustar(j))*1.27)
	416	qsalt(j)=(max(ustar(j)2-ustart(j)2,0.))/(RGhsalt(j))esalt
	417	! calculation of erosion (flux positive towards the surface here)
	418	! consistent with implicit resolution of turbulent mixing equation
	419	! Nemoto and Nishimura 2004 show that steady-state saltation is achieved within a time tau_eqsalt_bs of about 10s
	420	! we thus prevent snowerosion (snow particle transfer from the saltation layer to the first model level)
	421	! integrated over tau_eqsalt_bs to exceed the total mass of snow particle in the saltation layer
	422	! (rhoqsalthsalt)
	423	! during this first step we also lower bound the erosion to the amount of fresh snow accumulated during the time step
	424	maxerosion=min(precip_snow(j),hsalt(j)qsalt(j)rhod(j)/tau_eqsalt_bs)
	425
[4916]	426	fluxbs_1(j)=rhod(j)ws1(j)cdragh(j)zeta_bs(AcoefQBS(j)-qsalt(j)) &
	427	/ (1.-rhod(j)ws1(j)cdragh(j)zeta_bsBcoefQBS(j)*dtime)
	428	fluxbs_1(j)=max(-maxerosion,fluxbs_1(j))
	429
	430	if (precip_snow(j) .gt. abs(fluxbs_1(j))) then
	431	ok_remaining_freshsnow(j)=.true.
	432	bsweight_fresh(j)=1.
	433	else
	434	ok_remaining_freshsnow(j)=.false.
	435	bsweight_fresh(j)=exp(-(abs(fluxbs_1(j))-precip_snow(j))/precip_snow(j))
	436	endif
	437	else
	438	ok_remaining_freshsnow(j)=.false.
	439	fluxbs_1(j)=0.
	440	bsweight_fresh(j)=0.
	441	endif
[4835]	442	enddo
	443
	444
	445	! we now compute the snow age of the overlying layer (snow surface after erosion of the fresh snow accumulated during the time step)
	446	! this is done through the routine albsno
[4916]	447	CALL albsno(klon,knon,dtime,agesno(:),alb_neig(:), precip_snow(:)+fluxbs_1(:))
[4835]	448
	449	! 2nd step:
[4529]	450	! computation of threshold friction velocity
	451	! which depends on surface snow density
[4672]	452	do j = 1, knon
[4916]	453	if (ok_remaining_freshsnow(j)) then
	454	fluxbs_2(j)=0.
	455	else
	456	! we start eroding the underlying layer
[4523]	457	! estimation of snow density
	458	! snow density increases with snow age and
[4672]	459	! increases even faster in case of sedimentation of blowing snow or rain
[4835]	460	tau_dens=max(tau_densmin_bs, tau_dens0_bs*exp(-abs(precip_bs(j))/pbst_bs - &
	461	abs(precip_rain(j))/prt_bs)*exp(-max(tsurf(j)-RTT,0.)))
	462	rhos(j)=rhofresh_bs+(rhohard_bs-rhofresh_bs)(1.-exp(-agesno(j)86400.0/tau_dens))
[4523]	463	! blowing snow flux formula used in MAR
[4835]	464	ustart(j)=ustart0(j)exp(max(rhoice_bs/rhofresh_bs-rhoice_bs/rhos(j),0.))exp(max(0.,rhos(j)-rhohard_bs))
	465	! we have multiplied by exp to prevent erosion when rhos>rhohard_bs
	466	! computation of qbs at the top of the saltation layer
	467	! default formulation from MAR model (Amory et al. 2021, Gallee et al. 2001)
[4916]	468	esalt=1./(c_esalt_bs*max(1.e-6,ustar(j)))
[4835]	469	hsalt(j)=0.08436(max(1.e-6,ustar(j))*1.27)
	470	qsalt(j)=(max(ustar(j)2-ustart(j)2,0.))/(RGhsalt(j))esalt
	471	! calculation of erosion (flux positive towards the surface here)
	472	! consistent with implicit resolution of turbulent mixing equation
	473	! Nemoto and Nishimura 2004 show that steady-state saltation is achieved within a time tau_eqsalt_bs of about 10s
	474	! we thus prevent snowerosion (snow particle transfer from the saltation layer to the first model level)
	475	! integrated over tau_eqsalt_bs to exceed the total mass of snow particle in the saltation layer
	476	! (rhoqsalthsalt)
	477	maxerosion=hsalt(j)qsalt(j)rhod(j)/tau_eqsalt_bs
[4916]	478	fluxbs_2(j)=rhod(j)ws1(j)cdragh(j)zeta_bs(AcoefQBS(j)-qsalt(j)) &
	479	/ (1.-rhod(j)ws1(j)cdragh(j)zeta_bsBcoefQBS(j)*dtime)
	480	fluxbs_2(j)=max(-maxerosion,fluxbs_2(j))
	481	endif
[4523]	482	enddo
	483
[4916]	484
	485
	486
	487	! final flux and outputs
[4835]	488	do j=1, knon
[4916]	489	! total flux is the erosion of fresh snow +
	490	! a fraction of the underlying snow (if all the fresh snow has been eroded)
	491	! the calculation of the fraction is quite delicate since we do not know
	492	! how much time was needed to erode the fresh snow. We assume that this time
	493	! is dtexp(-(abs(fluxbs1)-precipsnow)/precipsnow)=dtbsweight_fresh
	494
	495	fluxbs(j)=fluxbs_1(j)+fluxbs_2(j)*(1.-bsweight_fresh(j))
[4672]	496	i = knindex(j)
	497	zxustartlic(i) = ustart(j)
	498	zxrhoslic(i) = rhos(j)
[4835]	499	zxqsaltlic(i)=qsalt(j)
	500	enddo
[4523]	501
	502
[4916]	503	else ! not ok_bs
[4835]	504	! those lines are useful to calculate the snow age
	505	CALL albsno(klon,knon,dtime,agesno(:),alb_neig(:), precip_snow(:))
[4523]	506
[4835]	507	endif ! if ok_bs
[4523]	508
[4835]	509
	510
[4523]	511	!****************************************************************************************
[4672]	512	! Calculate snow amount
[4523]	513	!
	514	!****************************************************************************************
	515	IF (ok_bs) THEN
[4526]	516	precip_totsnow(:)=precip_snow(:)+precip_bs(:)
	517	evap_totsnow(:)=evap(:)-fluxbs(:) ! flux bs is positive towards the surface (snow erosion)
[4523]	518	ELSE
[4526]	519	precip_totsnow(:)=precip_snow(:)
	520	evap_totsnow(:)=evap(:)
[4523]	521	ENDIF
[4672]	522
	523
[4523]	524	CALL fonte_neige(knon, is_lic, knindex, dtime, &
	525	tsurf, precip_rain, precip_totsnow, &
	526	snow, qsol, tsurf_new, evap_totsnow)
[4672]	527
	528
[4523]	529	WHERE (snow(1 : knon) .LT. 0.0001) agesno(1 : knon) = 0.
	530	zfra(1:knon) = MAX(0.0,MIN(1.0,snow(1:knon)/(snow(1:knon)+10.0)))
	531
	532
[3792]	533	END IF ! landice_opt
	534
	535
[781]	536	!****************************************************************************************
	537	! Send run-off on land-ice to coupler if coupled ocean.
[3903]	538	! run_off_lic has been calculated in fonte_neige or surf_inlandsis
[4283]	539	! If landice_opt>=2, corresponding call is done from surf_land_orchidee
[781]	540	!****************************************************************************************
[4283]	541	IF (type_ocean=='couple' .AND. landice_opt .LT. 2) THEN
	542	! Compress fraction where run_off_lic is active (here all pctsrf(is_lic))
	543	run_off_lic_frac(:)=0.0
	544	DO j = 1, knon
	545	i = knindex(j)
	546	run_off_lic_frac(j) = pctsrf(i,is_lic)
	547	ENDDO
	548
	549	CALL cpl_send_landice_fields(itime, knon, knindex, run_off_lic, run_off_lic_frac)
[781]	550	ENDIF
[1865]	551
	552	! transfer runoff rate [kg/m2/s](!) to physiq for output
	553	runoff(1:knon)=run_off_lic(1:knon)/dtime
	554
[1403]	555	snow_o=0.
	556	zfra_o = 0.
	557	DO j = 1, knon
	558	i = knindex(j)
	559	snow_o(i) = snow(j)
	560	zfra_o(i) = zfra(j)
	561	ENDDO
	562
	563
[2227]	564	!albedo SB >>>
	565	select case(NSW)
	566	case(2)
	567	alb_dir(1:knon,1)=alb1(1:knon)
	568	alb_dir(1:knon,2)=alb2(1:knon)
	569	case(4)
	570	alb_dir(1:knon,1)=alb1(1:knon)
	571	alb_dir(1:knon,2)=alb2(1:knon)
	572	alb_dir(1:knon,3)=alb2(1:knon)
	573	alb_dir(1:knon,4)=alb2(1:knon)
	574	case(6)
	575	alb_dir(1:knon,1)=alb1(1:knon)
	576	alb_dir(1:knon,2)=alb1(1:knon)
	577	alb_dir(1:knon,3)=alb1(1:knon)
	578	alb_dir(1:knon,4)=alb2(1:knon)
	579	alb_dir(1:knon,5)=alb2(1:knon)
	580	alb_dir(1:knon,6)=alb2(1:knon)
[3900]	581
[3901]	582	IF ((landice_opt .EQ. 1) .AND. (iflag_albcalc .EQ. 2)) THEN
[3900]	583	alb_dir(1:knon,1)=alb6(1:knon,1)
	584	alb_dir(1:knon,2)=alb6(1:knon,2)
	585	alb_dir(1:knon,3)=alb6(1:knon,3)
	586	alb_dir(1:knon,4)=alb6(1:knon,4)
	587	alb_dir(1:knon,5)=alb6(1:knon,5)
	588	alb_dir(1:knon,6)=alb6(1:knon,6)
	589	ENDIF
	590
[2227]	591	end select
	592	alb_dif=alb_dir
	593	!albedo SB <<<
	594
	595
[781]	596	END SUBROUTINE surf_landice
	597	!
	598	!****************************************************************************************
	599	!
	600	END MODULE surf_landice_mod
	601
	602
	603

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