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LWup passed from CLM to CAM disagreement

E

eaton

CSEG and Liaisons
Yes, I am seeing the large differences at cell locations which are all land just as you've pointed out.  I didn't expect this and don't have an explanation.  The code will need to be traced from where the values are set in CLM through the coupler layer to come to a resolution.  I'll venture a guess that perhaps the LWup output from CLM is not exactly what's being passed to the coupler.  Otherwise it would appear that the coupler is doing something unexpected.
 
C

ckuo@lbl_gov

Member
Hello Eaton,The lwup differences over land also occurs for f09_g16, f19_g16 grids for CESM1.2.2, and CESM1.0.6 with T31_g37 grid.  All tested with compset B1850C5CN.From CLM, 'eflx_lwrad_out' is the variable output to history fields as 'LWup' and also passed to the coupler through 'index_l2x_Fall_lwup'.  From the cesm1_2_2/models/atm/cam/src/cpl_*/atm_comp_*.F90 codes:  cam_in%lwup = index_x2a_Faxx_lwup.Is there any reason that there would be large differences occuring over land during the merge of lwup (land, ocean, ice) in the coupler?Thanks,Kuo 
 
C

ckuo@lbl_gov

Member
Hello Eaton,The lwup differences over land also occurs for f09_g16, f19_g16 grids for CESM1.2.2, and CESM1.0.6 with T31_g37 grid.  All tested with compset B1850C5CN.From CLM, 'eflx_lwrad_out' is the variable output to history fields as 'LWup' and also passed to the coupler through 'index_l2x_Fall_lwup'.  From the cesm1_2_2/models/atm/cam/src/cpl_*/atm_comp_*.F90 codes:  cam_in%lwup = index_x2a_Faxx_lwup.Is there any reason that there would be large differences occuring over land during the merge of lwup (land, ocean, ice) in the coupler?Thanks,Kuo 
 
C

ckuo@lbl_gov

Member
Hello Eaton,The lwup differences over land also occurs for f09_g16, f19_g16 grids for CESM1.2.2, and CESM1.0.6 with T31_g37 grid.  All tested with compset B1850C5CN.From CLM, 'eflx_lwrad_out' is the variable output to history fields as 'LWup' and also passed to the coupler through 'index_l2x_Fall_lwup'.  From the cesm1_2_2/models/atm/cam/src/cpl_*/atm_comp_*.F90 codes:  cam_in%lwup = index_x2a_Faxx_lwup.Is there any reason that there would be large differences occuring over land during the merge of lwup (land, ocean, ice) in the coupler?Thanks,Kuo 
 
C

ckuo@lbl_gov

Member
Hello Eaton,The lwup differences over land also occurs for f09_g16, f19_g16 grids for CESM1.2.2, and CESM1.0.6 with T31_g37 grid.  All tested with compset B1850C5CN.From CLM, 'eflx_lwrad_out' is the variable output to history fields as 'LWup' and also passed to the coupler through 'index_l2x_Fall_lwup'.  From the cesm1_2_2/models/atm/cam/src/cpl_*/atm_comp_*.F90 codes:  cam_in%lwup = index_x2a_Faxx_lwup.Is there any reason that there would be large differences occuring over land during the merge of lwup (land, ocean, ice) in the coupler?Thanks,Kuo 
 
C

ckuo@lbl_gov

Member
Solution!2 steps were required:1. iradlw=1 & iradlw=1 in user_nl_cam, so that CAM runs every timestep.  It is defaulted to run every hour.  This was confusing because the coupler is defaulted to couple CAM and CLM every half an hour (ATM_NCPL=48)2. comparson made between CLM(timestep_j) = CAM(timestep_j+1)
 
C

ckuo@lbl_gov

Member
Solution!2 steps were required:1. iradlw=1 & iradlw=1 in user_nl_cam, so that CAM runs every timestep.  It is defaulted to run every hour.  This was confusing because the coupler is defaulted to couple CAM and CLM every half an hour (ATM_NCPL=48)2. comparson made between CLM(timestep_j) = CAM(timestep_j+1)
 
C

ckuo@lbl_gov

Member
Solution!2 steps were required:1. iradlw=1 & iradlw=1 in user_nl_cam, so that CAM runs every timestep.  It is defaulted to run every hour.  This was confusing because the coupler is defaulted to couple CAM and CLM every half an hour (ATM_NCPL=48)2. comparson made between CLM(timestep_j) = CAM(timestep_j+1)
 
C

ckuo@lbl_gov

Member
Solution!2 steps were required:1. iradlw=1 & iradlw=1 in user_nl_cam, so that CAM runs every timestep.  It is defaulted to run every hour.  This was confusing because the coupler is defaulted to couple CAM and CLM every half an hour (ATM_NCPL=48)2. comparson made between CLM(timestep_j) = CAM(timestep_j+1)
 
E

eaton

CSEG and Liaisons
Thanks for the information.  I'm not surprised that comparing different timesteps was required.  There is a flag that is passed through the coupler that tells the surface components when CAM is about to do a radiation calculation and that they should calculate the surface albedos and pass them back to CAM.  Then on the subsequent timestep CAM has the albedos it needs to do its radiation calculation.  This is a complicated part of the model coupling which I'm not very familiar with.  Glad you were able to sort this out. 
 
E

eaton

CSEG and Liaisons
Thanks for the information.  I'm not surprised that comparing different timesteps was required.  There is a flag that is passed through the coupler that tells the surface components when CAM is about to do a radiation calculation and that they should calculate the surface albedos and pass them back to CAM.  Then on the subsequent timestep CAM has the albedos it needs to do its radiation calculation.  This is a complicated part of the model coupling which I'm not very familiar with.  Glad you were able to sort this out. 
 
E

eaton

CSEG and Liaisons
Thanks for the information.  I'm not surprised that comparing different timesteps was required.  There is a flag that is passed through the coupler that tells the surface components when CAM is about to do a radiation calculation and that they should calculate the surface albedos and pass them back to CAM.  Then on the subsequent timestep CAM has the albedos it needs to do its radiation calculation.  This is a complicated part of the model coupling which I'm not very familiar with.  Glad you were able to sort this out. 
 
E

eaton

CSEG and Liaisons
Thanks for the information.  I'm not surprised that comparing different timesteps was required.  There is a flag that is passed through the coupler that tells the surface components when CAM is about to do a radiation calculation and that they should calculate the surface albedos and pass them back to CAM.  Then on the subsequent timestep CAM has the albedos it needs to do its radiation calculation.  This is a complicated part of the model coupling which I'm not very familiar with.  Glad you were able to sort this out. 
 
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