Hi community,
I am trying to use CRTM 2.4.0 to simulate IR BTs at 3.9 um. However, it seems that the sun glint effect is not simulated according to my results. My question is do I have to turn on any switch to allow CRTM to take into account sun glint effect?
Best,
Lijian
Hi @cxzydn, welcome to the forum!
Can you provide more details about your calculation, a description of what you are doing exactly and a minimal code example to reproduce the potential issue?
Hi Stegmann,
Thank you for your reply!
I tried to use ERA5 data to simulate clear sky GOES-16 ABI BTs. The fortran program I use is modified from an example program named Example5_clearsky.f90 from an old version of CRTM.
Here are some sample codes in the program:
127 Error_Status = CRTM_Init( (/Sensor_Id/), & ! Input… must be an array, hence the (/…/)
128 ChannelInfo , & ! Output
129 ! EmisCoeff_File=‘FASTEM5.MWwater.EmisCoeff.bin’, &
130 ! IRwaterCoeff_File=‘WuSmith.IRwater.EmisCoeff.bin’,&
131 File_Path=‘./CRTM_v2.3.0/Big_Endian/’)
181 READ(Unitin,,err=200,end=200)N_LAYERS,Lat,lon
182 READ(Unitin,)AZIMUTH_ANGLE,ZENITH_ANGLE,SOURCE_AZIMUTH_ANGLE,SOURCE_ZENITH_ANGLE
183 IF (SOURCE_AZIMUTH_ANGLE .lt. 0) SOURCE_AZIMUTH_ANGLE = SOURCE_AZIMUTH_ANGLE + 360.
184 READ(Unitin,*)Sur_Type,Sur_Temp,u10m,v10m
185 CALL CRTM_RTSolution_Create(RTSolution,N_LAYERS)
186 CALL CRTM_Atmosphere_Create( Atm, N_LAYERS, N_ABSORBERS, N_CLOUDS, N_AEROSOLS )
255 Atm(1)%Climatology = US_STANDARD_ATMOSPHERE
256 Atm(1)%Absorber_Id = (/ H2O_ID , O3_ID /)
257 Atm(1)%Absorber_Units = (/ MASS_MIXING_RATIO_UNITS, VOLUME_MIXING_RATIO_UNITS /)
258 READ(Unitin,)Atm(1)%Level_Pressure(0:N_LAYERS)
259 READ(Unitin,)Atm(1)%Pressure(1:N_LAYERS)
260 READ(Unitin,)Atm(1)%Temperature(1:N_LAYERS)
261 READ(Unitin,)Atm(1)%Absorber(1:N_LAYERS,1)
262 READ(Unitin,*)Atm(1)%Absorber(1:N_LAYERS,2)
292 CALL CRTM_Geometry_SetValue( Geometry, &
293 Longitude = Lon,&
294 Latitude = Lat,&
295 Sensor_Zenith_Angle = ZENITH_ANGLE, &
296 Sensor_Azimuth_Angle = AZIMUTH_ANGLE, &
297 Source_Zenith_Angle = SOURCE_ZENITH_ANGLE,&
298 Source_Azimuth_Angle = SOURCE_AZIMUTH_ANGLE )
299 ! ============================================================================
300 Error_Status = CRTM_Forward( Atm , &
301 Sfc , &
302 Geometry , &
303 ChannelInfo, &
304 RTSolution, &
305 Options = Opt )
The codes work well but the problem is the sun glint effect can not be simulated. I also checked the CRTM source codes and found this is likely related to the CRTM_BRDF_SfcOptics module. I wonder if there is any extra sun glint option in CRTM that i need to turn on? hope you could help me out.
Thank you, but we would need a fully working minimal example of your code and a description of what kind of output you are looking for, and what you are seeing instead.
Otherwise we cannot provide any help.
As a follow up and general question, is oceanic sun glint handled in visible wavelengths by CRTM?