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How to get cloud fracrtion from wrfout outputs over regions with different elevations?


New member
Hello, everyone!
I tried to get cloud fraction over regions with different elevations (e.g. the Tibetan Plateau, the Sichuan Basin). The low, middle and high clouds can be obtained by the funtion of "wrf_user_getvar(cfrac)" in NCL. The default criterion of low, middle and high clouds is height. However, when compared with the ERA5 reanalysis, the spatial distribution of the three kinds of clouds was unreasonable. Here I just present the low clouds in Figure 1. I thought the terrain height should be added to the "height", but it seems hard to add it in the code (Figure 2). Then, I used the "pressure" to acquire the cloud fraction and the distribution was also unreasonable (Figure 3). I wonder how to get the three kinds of cloud fraction over regions with varing elevations from wrfout data?
Thanks for any help!


For clarification purposes, are you interested in how to do this, specifically with NCL (or some type of post-processing)? Or are you asking if there are model settings that can be modified to give you the results you expect?
Hi, kwerner!
I thought the above results from the wrfout data were not correct and I'm interested in how to get the proper distribution of cloud fraction from wrfout outputs. I'm not working on the improvement of cloud simulation in WRF.
Maybe the result from the ERA5 is not real and I just utilize the ERA5 as a comparison.
Thanks for the clarification. I spoke to our physics specialist about this. They said there must be a different definition in ERA5 because normally low/mid/high come from pressure levels. So the Tibetan Plateau would not show low clouds because the surface is above that threshold. You'll need to find the ERA5 definitions. Are they defined above ground level instead? That would explain the differences.