High Model Temperature Bias

[hannay]

Scientific validation of CESM consists of a multi-decadal model run of the given component set at the target resolution, followed by scientific review of the model output diagnostics. All scientifically supported component sets are also accompanied by diagnostic and model output data. If a comspet is not scientifically validated, it means we didn't go through thsi process. But it doesn't mean that you would get something incorrect. It just means that we didn't test this configuration. So you would have to do a run (long enough enough - the length depends which component you are looking at), then analyze the simulation to make sure it looks fine. You could compare with another run. For teh atmosphere, you would loke to cloud forcing, radiative fluxes, precipitation, TS, for instance. 

 

[rangel@lamce_coppe_ufrj_br]

Hello, I'm having the same issue (before your update), but I'm using CESM version 2.0.I'm using the BHIST compset, running from 1850 to 2005, and the RESTOM time series is showing considerably different values from the ones available at http://www.cesm.ucar.edu/models/cesm2/scientifically-validated-cesm2.html.Well, the resolution I'm using is not scientifc validated (f19_g17), but could it be the reason for those considerably differences? Or perhaps I'm missing something in the calculations?Here are the steps:1) read FSNT and FLNT from every 1872 CAM output files(from 1850-01-01 to 2005-01-01) and put each one into a 144x96x1872 variable.2) calculate the means: first over longitude, then latitude for each variable.3) RESTOM=FSNT(from step 2)-FLNT(from step 2)I plotted the time series and you can find it attached (b.e20.bhist.f19_g17.gsm.dsc.001.png) as well as NCAR's times series (b.e20.BHIST.f09_g17.20thC.297_05_surf.gif) for comparison. I don't know what I'm doing wrong ... Could you, please, give more details about:"I just realized I had to do a weighted spatial average and I got -0.02 W/m2."   ? Cheers,Rafael 

 

[rangel@lamce_coppe_ufrj_br]

Hello, I'm having the same issue (before your update), but I'm using CESM version 2.0.I'm using the BHIST compset, running from 1850 to 2005, and the RESTOM time series is showing considerably different values from the ones available at http://www.cesm.ucar.edu/models/cesm2/scientifically-validated-cesm2.html.Well, the resolution I'm using is not scientifc validated (f19_g17), but could it be the reason for those considerably differences? Or perhaps I'm missing something in the calculations?Here are the steps:1) read FSNT and FLNT from every 1872 CAM output files(from 1850-01-01 to 2005-01-01) and put each one into a 144x96x1872 variable.2) calculate the means: first over longitude, then latitude for each variable.3) RESTOM=FSNT(from step 2)-FLNT(from step 2)I plotted the time series and you can find it attached (b.e20.bhist.f19_g17.gsm.dsc.001.png) as well as NCAR's times series (b.e20.BHIST.f09_g17.20thC.297_05_surf.gif) for comparison. I don't know what I'm doing wrong ... Could you, please, give more details about:"I just realized I had to do a weighted spatial average and I got -0.02 W/m2."   ? Cheers,Rafael 

 

[hannay]

The gridboxes don't all have the same size. The gridbox have a larger area near the equator and a smaller area near the pole.
There should be a variable in the file gw that give you the weigh of each gridbox.

You need to do a weigthed average:

RESTOM [/i]= SUM[/b] [RESTOM[/i]*gw[/i]]/SUM[/b][gw[/i]]

There are function in ncl that allows you to do this:
https://www.ncl.ucar.edu/Document/Functions/Contributed/dim_avg_wgt_n_Wrap.shtml

 

[hannay]

The gridboxes don't all have the same size. The gridbox have a larger area near the equator and a smaller area near the pole.
There should be a variable in the file gw that give you the weigh of each gridbox.

You need to do a weigthed average:

RESTOM [/i]= SUM[/b] [RESTOM[/i]*gw[/i]]/SUM[/b][gw[/i]]

There are function in ncl that allows you to do this:
https://www.ncl.ucar.edu/Document/Functions/Contributed/dim_avg_wgt_n_Wrap.shtml

 

[rangel@lamce_coppe_ufrj_br]

Hi Cecile,thanks for you answer.I calculated it again, and the result for RESTOM (BHIST run with f19_g17 resolution and unsupported) is 0.0095. I think it is too small.What I did (Matlab code):1) Read FLNT and FSNT from 1872 monthly results;>> whos FSNT FLNT gw
  Name        Size                     Bytes  Class     Attributes

  FLNT      144x96x1872            103514112  single             
  FSNT      144x96x1872            103514112  single             
  gw         96x1                        768  double 2) Calculate restom:restom = FSNT-FLNT; 3) Preparing for the weighted average:gw_2D=repmat(gw,[1,144])';                                    %create a variable with the gw first column repeated 144 times
gw_3D = repmat(gw_2D,1,1,size(restom,3));            %create a variable with the previous 2D variable repeated 1872 times
restom_lat_weighted = restom.*gw_3D;                   %multiplies every latitude and time by gw 4) Averaging: a=mean(restom_lat,1);      %mean over the longitudes
 b=mean(a,2);                    %mean over latitudes
 c=mean(b,3);                     %mean over time
RESTOM=c/(sum(gw))       The result is: RESTOM=0.0095 What am I doing wrong? I checked the code and tried different ways of calculation, but always had the same result.Here: http://www.cesm.ucar.edu/working_groups/Atmosphere/metrics.html it says that restom for 1850 coupled should be close to zero, but 0.0095 is too close...

 

[rangel@lamce_coppe_ufrj_br]

Hi Cecile,thanks for you answer.I calculated it again, and the result for RESTOM (BHIST run with f19_g17 resolution and unsupported) is 0.0095. I think it is too small.What I did (Matlab code):1) Read FLNT and FSNT from 1872 monthly results;>> whos FSNT FLNT gw
  Name        Size                     Bytes  Class     Attributes

  FLNT      144x96x1872            103514112  single             
  FSNT      144x96x1872            103514112  single             
  gw         96x1                        768  double 2) Calculate restom:restom = FSNT-FLNT; 3) Preparing for the weighted average:gw_2D=repmat(gw,[1,144])';                                    %create a variable with the gw first column repeated 144 times
gw_3D = repmat(gw_2D,1,1,size(restom,3));            %create a variable with the previous 2D variable repeated 1872 times
restom_lat_weighted = restom.*gw_3D;                   %multiplies every latitude and time by gw 4) Averaging: a=mean(restom_lat,1);      %mean over the longitudes
 b=mean(a,2);                    %mean over latitudes
 c=mean(b,3);                     %mean over time
RESTOM=c/(sum(gw))       The result is: RESTOM=0.0095 What am I doing wrong? I checked the code and tried different ways of calculation, but always had the same result.Here: http://www.cesm.ucar.edu/working_groups/Atmosphere/metrics.html it says that restom for 1850 coupled should be close to zero, but 0.0095 is too close...

 

[hannay]

The order of magnitude for RESTOM is:RESTOM very close to zero in 1850RESTOM ~ 0.8 W/m2 at the end of the 20th century (from CERES-EBAF)These numbers are just guidance and  it will depend on how you tuned your model. You adjust RESTOM by tuning the model. For instance, in recent runs we have RESTOM = 0.4 W/m2 for the period 1991-2005http://webext.cgd.ucar.edu/B20TH/b.e20.BHIST.f09_g17.20thC.297_01/atm/b.e20.BHIST.f09_g17.20thC.297_01_yrs1991-2005-b.e20.BHIST.f09_g16.20thC.125.02_yrs1991-2005/set1/table_GLBL_ANN.asc I am not sure thsi answers your question. I am not sure what you mean by "0.0095 is too close..." 

 

[hannay]

The order of magnitude for RESTOM is:RESTOM very close to zero in 1850RESTOM ~ 0.8 W/m2 at the end of the 20th century (from CERES-EBAF)These numbers are just guidance and  it will depend on how you tuned your model. You adjust RESTOM by tuning the model. For instance, in recent runs we have RESTOM = 0.4 W/m2 for the period 1991-2005http://webext.cgd.ucar.edu/B20TH/b.e20.BHIST.f09_g17.20thC.297_01/atm/b.e20.BHIST.f09_g17.20thC.297_01_yrs1991-2005-b.e20.BHIST.f09_g16.20thC.125.02_yrs1991-2005/set1/table_GLBL_ANN.asc I am not sure thsi answers your question. I am not sure what you mean by "0.0095 is too close..." 

 

[hannay]

Also  beware RESTOM has large year-to-year variations. This is becasue this is the difference of 2 large numbers very close to each other. You can plot the timeseries of RESTOM to have a sense of the variability.

 

[hannay]

Also  beware RESTOM has large year-to-year variations. This is becasue this is the difference of 2 large numbers very close to each other. You can plot the timeseries of RESTOM to have a sense of the variability.

 

[Wenhui Tang]

1) Firstly I was wondering what radiation variables from CAM5 are used to compute the radiative balance. Is is something like FSNTOA+FSNIRTOA = RESTOM or is it calculated using other variables? In CAM5: RESTOM = FSNT - FLNT
2) Is the method any different because I will be tuning a current year time period (2001-2010) instead of pre-industrial (1850)? The difference would be that you are not in radiative equilibrium for current time
1850 => RESTOM = 0 W/m2
2000 => RESTOM will be positive (in CERES_EBAF it is close to 0.8 W/m2)
3) I also did some checking on the LWCF and SWCF from my simulations compared against CERES data. It appears that on global average the SWCF from my simulations is around 5.0 W m-2 greater (more negative) than CERES and the LWCF is about 2.0 W m-2 smaller. Based on that is there any parameters to tune that make the SWCF less negative and increase the LWCF? increasing rhminl will allow you to decrease SWCF (less negative) without affecting too much LWCF, but 5 W/m2 is a lot so it depends where your rhminl is nowDecreasing Dcs might help tooFOR SWCF: are you comparing to CERES or CERES-EBAF ? 4) Lastly, is there an acceptable range of values with which to adjust the parameters that you suggested to be physically realistic?rhminl is not an observable. This is the threshold from low-level cloud and it is used in the model as a tuning parameter. Personally, I have pushed it up to 0.93.Dcs = [90-500] is probably a reasonable range (these values are coming from Andrew Gettelman). Dcs is the effective diameter at which we autoconvert to precipitation for ice crystals. So it could be refined based on observations.

Hello, I'm new to CESM. I have been studying radiation recently, and I have some confusion. I would like to ask you for advice. Is long wave cloud radiation(LWCF) upward or downward or net? Is it positive down or positive up? The same question applies to shortwave cloud radiation (SWCF). I would appreciate it if you could answer my questions.