Changing the rotation of the planet

[bethproedrou@gmail_com]

Hello everyone,
Is there a way to change the rotation rate of the planet in CESM 1.0.4? I would like to run a simulation using the F_2000_WACCM compset, where the Earth's rotation rate would be half of what it currently is.

Thank you in advace,
Beth

 

[rneale]

In models/csm_share/shr/shr_const_mod.F90 change the siderial day to half it's current value (currently SHR_CONST_SDAY    = 86164.0_R8)Rich

 

[bethproedrou@gmail_com]

Thank you very much Rich. Indeed it worked. Though now I am having a different problem. I am trying to make the Earth tidally locked. However the model crashes at approximately 15:00 UT (if the simulation runs for less than that the program finishes without a problem). In the error logs it says that the mixing ratio has been violated. I was wondering if anyone knows why. In the error logs it says that the mixing ratio has been violated. Which I guess is understandable. What I do not understand is why it takes so long for such an error to appear. And is there a way to avoid it? Perhaps slowly reduce the rotation of the planet? But how long would that take? Thank you in advance,Beth

 

[rneale]

Beth, the change in rotation maybe a shock to the system that leads to a crash. It might be useful to run with a shorter timestep (DTIME) to enable the climate to adjust back to equilibrium.

 

[bethproedrou@gmail_com]

Dr. Neale, thank you very much for the suggestion, I had not thought of that. Would you happen to know what is the shortest timestep that CESM supports? I do not remember it being mentioned anywhere in the Technical Note.

 

[bethproedrou@gmail_com]

I have tried reducing the timestep to 1 second but the model still crashes at around 22:00 UT. The error model that appears this time is:  BalanceCheck: soil balance error nstep =     36000 point =  1885 imbalance =    0.000001 W/m2forrtl: severe (174): SIGSEGV, segmentation fault occurredThe error appears for points 0 to 36000.

 

[rneale]

Beth, a further suggestion could be to increase the rotation more rate gradually to see if the model can tolerate even small changes, say 10% higher than the default first, rather than 100%

 

[bethproedrou@gmail_com]

It can. Actually I managed to fix the problem after all. One just needs to change the shr_const_mod.F90 file in several folders:cesm1_0_4/models/csm_share/shr/cesm1_0_4/models/lnd/clm/tools/mkgriddata/cesm1_0_4/models/lnd/clm/tools/mksurfdata/cesm1_0_4/models/lnd/clm/tools/interpinic/cesm1_0_4/models/lnd/clm/tools/mkdatadomain/ Also one needs to make sure that the timestep is changed in the $CASES/$CASE/Buildconf/cam.buildnml.csh. Otherwise inconsistencies arise.  

 

[bethproedrou@gmail_com]

Now I have a new problem. Even though the model did compile and run, it seems that the planet's rotation rate has not changed. The shortwave downward radiation is not stationary over one point of the planet (as it should be in the case of a tidally locked planet) but rather moves in the same speed and direction as when the amount of seconds per day were normal amount (86164). Does anyone know how I could fix this? I tried a few things but none of them worked so far. Thank you very much in advance,Beth

 

[agya0509@gmail_com]

Hello, I am trying to change rotation of an aquaplanet in CESM1_2_0 .but even after reducing the siderial day value to its half ,i am not getting the correct change.Please tell me if there is another way to do it .Thank you in advance  

 

[bethproedrou@gmail_com]

Apart from changing the siderial day you should also change:APTIME in apex_subs.F90. It controls how many degrees the earth is rotating. Beth

 

[agya0509@gmail_com]

Thank you so much. I ll do that.

 

[rajuphyamu@gmail_com]

I am running CESM CAM5.1 in aqua planet mode for double rotation and makes some changes in filesshr_const_mod.F90 by changing CDAY (43200) and SDAY (43082) apart from this i also changed APTIME in apex_subs.F90but the flux (diurnal behavior) at a point doesnt change.I am not getting why diurnal behavior is not changing.
I request you for any type of suggestions and helpThank You in advance