crash from increased surface albedo

[micah_wilhelm@env_ethz_ch]

I'm trying to increase the surface albedo over all land surface by 0.05 in a standard AMIP compset (f.e104.F_AMIP_CN.f19_f19).I made the following modification in the SurfaceAlbedo.F90 subroutine TwoStream:          ! Flux reflected by vegetation! MW          albi(p,ib) = h7 + h8 + 0.05! MWI do the same modification with direct albedo.However, this crashes after several years of running. I'm really sure why though. My supervisor did the same simulation with COSMO-CLM2 (CLM on a regional domain).My error in the ccsm.log file:
 BalanceCheck: soil balance error nstep =      8290 point =  2907 imbalance =   -0.000001 W/m2
 QNEG4 WARNING from TPHYSAC  Max possible LH flx exceeded at    1 points. , Worst excess =  -1.7578E-07, lchnk = 792, i =    1, same as indices lat =  76, lon =  99
 urban net longwave radiation error: no convergence
 clm model is stopping

I was thinking that maybe it makes some grid cells > 1 for instance if the snow fraction is high and hence already close to 1 before my adjustment. In fact I would not like to affect the snowcover at all (only the combine soil and vegitation albedos). I tried to scale the increase by the fraction of snow cover, but this crashes after 3 times steps: albi(p,ib) = albi(p,ib) + 0.05*(1._r8-frac_sno(p))

The problem still remains that I increase albedo over lakes and wetlands and glaciers, I would prefer not to, but I don't know how :( 

 

[slevis]

Dear Micah,I'm not certain without investigating more carefully, but I suspect the following:You introduced your change too late in the algorithm and an albedo without your change is being used by the model, so your change leads to an inconsistency and an energy imbalance. Maybe I'm wrong but, if not, try tracing the clm albedo calculation back to earlier in the algorithm to avoid such inconsistency.Sam Levis

 

[zp_xie@foxmail_com]

HiHave you sloved your problem?  And would you like to give me some tips to change the albedo correctily in the SurfaceAlbedo.F90 or other places.Thanks very much !Xie