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bas

Low, Middle and high clouds

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Hi everyone,

 

I want to calculate low, middle and high clouds from my WRF output. I have many cloud related fields in the wrfout file such as  cloud fraction, cloud water mixing ratio, RH, graupel mixing ratio, water vapor mixing ratio etc., but not sure how to calculate what i want.

 

Will greatly appreciate any help.

 

bas:)

 

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If you just want a binary representation of cloud forecast by the model, you just need to use the QCLOUD field. This is cloud water mixing ratio and it will be greater than zero only at grid points where clouds have been initiated by the microphysics scheme. Then you can flag these non-zero QCLOUD points as being within certain height ranges (say like 0=low, 1=middle, 2=high clouds).

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If you just want a binary representation of cloud forecast by the model, you just need to use the QCLOUD field. This is cloud water mixing ratio and it will be greater than zero only at grid points where clouds have been initiated by the microphysics scheme. Then you can flag these non-zero QCLOUD points as being within certain height ranges (say like 0=low, 1=middle, 2=high clouds).

Hi there; thanks for your help. The QCloud field does not show any clouds at any (low, middle and high) level and the entire field has 0 values, however when i use low middle and high clouds (clflo, clfmi and clfhi) from GrADS, i can see some middle level clouds at almost the same location as i  get from satellite imagery. GrADS calculates clflo, clfmi, and clfhi using RH and not qc field. I just can't understand why there is such a large  discrepency and which calc is should consider correct. I would appreciate if you could comment on this.

 

Since its a high res simulation (500 m) i am not using any cumulus parameterization. I used three different micro-physics schemes (WSM6, Lin et al. and Thompson) and getting the same results.

 

best, 

bas:)

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Hi there; thanks for your help. The QCloud field does not show any clouds at any (low, middle and high) level and the entire field has 0 values, however when i use low middle and high clouds (clflo, clfmi and clfhi) from GrADS, i can see some middle level clouds at almost the same location as i  get from satellite imagery. GrADS calculates clflo, clfmi, and clfhi using RH and not qc field. I just can't understand why there is such a large  discrepency and which calc is should consider correct. I would appreciate if you could comment on this.

 

Since its a high res simulation (500 m) i am not using any cumulus parameterization. I used three different micro-physics schemes (WSM6, Lin et al. and Thompson) and getting the same results.

 

best, 

bas:)

 

Is there precipitation during the model run period (if there "should be")? If the microphysics scheme is producing rain it must also be initiating cloud regions. Double check to see if there any non-zero QCLOUD regions with ncdump like

ncdump -v QCLOUD your_wrf_output.nc >& wrf_qcloud.txt

to put the QCLOUD field for the entire domain into the text file. You may have to append a '.nc' to the wrf output file. The text file will likely be pretty long but quickly scrolling through you should be able to see if any values are non-zero.

 

Also, what model source are using to initialize the WRF? If there is no RH field being input into the WRF the model won't produce any cloud or precip.

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