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ARWpost and cloud fractions

PostPosted: Tue Jul 14, 2015 8:29 am
by tanksnr
Hi all,

Related to viewtopic.php?f=30&t=6939 but going a bit further.

I'm interested in using WRF's simulated cloud fraction (total column).

Two ways to do this is to use WRF's CLDFRA or ARWpost's CLFLO~HI.
I'm trying ARWpost first.

CLFLO~HI is calculated by calc_clfr routine using max RH within the predefined layer heights. Why is this? And why not use CLDFRA?
What exactly does the routine do, i.e. if I want to get total colum cloud fraction do I take average of LO, MI and HI? Or do I take the max (sounds more likely)?

Failing use of CLFLO~HI, is it a simple matter of getting ARWpost to output just CLDFRA, instead of having to output "all" fields into one file?

Re: ARWpost and cloud fractions

PostPosted: Thu Jul 16, 2015 5:45 am
by tanksnr
Ok I found a very insightful post regarding what ARWpost is doing: http://strc.comet.ucar.edu/library/lists/wrfems/2010-March/000481.html

I also found out what CLDFRA is: http://www.emc.ncep.noaa.gov/GFS/doc.php#clofrac

However it still doesn't answer the question as to why not use CLDFRA in calculating a cloud fraction in ARWpost (as is/was done in WRFpost). I cannot find code for WRFpost to see how to integrate the entire cloud fraction over total column.