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GHT 500mb

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francescomaicu

Member
Dear WRF supporters,
Since I'm running WRF4.2 forced with GDAS data, I want to extract the Geopotential height of the 500mb from the input data to compare with the modeled one.
In the grib files HGT (not GHT) is calculated on 41 levels,
Code: 
12:3828097:d=2020091500:HGT Geopotential Height [gpm]:0.4 mb:anl:
16:6108583:d=2020091500:HGT Geopotential Height [gpm]:1 mb:anl:
22:8801582:d=2020091500:HGT Geopotential Height [gpm]:2 mb:anl:
28:11472164:d=2020091500:HGT Geopotential Height [gpm]:3 mb:anl:
34:14279082:d=2020091500:HGT Geopotential Height [gpm]:5 mb:anl:
40:17083272:d=2020091500:HGT Geopotential Height [gpm]:7 mb:anl:
46:19602944:d=2020091500:HGT Geopotential Height [gpm]:10 mb:anl:
53:22800206:d=2020091500:HGT Geopotential Height [gpm]:15 mb:anl:
57:25115304:d=2020091500:HGT Geopotential Height [gpm]:20 mb:anl:
64:28537495:d=2020091500:HGT Geopotential Height [gpm]:30 mb:anl:
71:33015866:d=2020091500:HGT Geopotential Height [gpm]:40 mb:anl:
75:35831433:d=2020091500:HGT Geopotential Height [gpm]:50 mb:anl:
88:41728732:d=2020091500:HGT Geopotential Height [gpm]:70 mb:anl:
95:46572296:d=2020091500:HGT Geopotential Height [gpm]:100 mb:anl:
110:54334473:d=2020091500:HGT Geopotential Height [gpm]:150 mb:anl:
125:61819049:d=2020091500:HGT Geopotential Height [gpm]:200 mb:anl:
140:69091051:d=2020091500:HGT Geopotential Height [gpm]:250 mb:anl:
155:76951631:d=2020091500:HGT Geopotential Height [gpm]:300 mb:anl:
170:85030075:d=2020091500:HGT Geopotential Height [gpm]:350 mb:anl:
185:92791893:d=2020091500:HGT Geopotential Height [gpm]:400 mb:anl:
200:100594266:d=2020091500:HGT Geopotential Height [gpm]:450 mb:anl:
214:107159330:d=2020091500:HGT Geopotential Height [gpm]:500 mb:anl:
229:114949462:d=2020091500:HGT Geopotential Height [gpm]:550 mb:anl:
243:122494241:d=2020091500:HGT Geopotential Height [gpm]:600 mb:anl:
257:130046047:d=2020091500:HGT Geopotential Height [gpm]:650 mb:anl:
271:137615885:d=2020091500:HGT Geopotential Height [gpm]:700 mb:anl:
286:146226885:d=2020091500:HGT Geopotential Height [gpm]:750 mb:anl:
300:153966060:d=2020091500:HGT Geopotential Height [gpm]:800 mb:anl:
314:161878224:d=2020091500:HGT Geopotential Height [gpm]:850 mb:anl:
329:171229811:d=2020091500:HGT Geopotential Height [gpm]:900 mb:anl:
343:179428139:d=2020091500:HGT Geopotential Height [gpm]:925 mb:anl:
357:187480920:d=2020091500:HGT Geopotential Height [gpm]:950 mb:anl:
372:195479235:d=2020091500:HGT Geopotential Height [gpm]:975 mb:anl:
401:211187644:d=2020091500:HGT Geopotential Height [gpm]:1000 mb:anl:
403:212974397:d=2020091500:HGT Geopotential Height [gpm]:surface:anl:
444:232723185:d=2020091500:HGT Geopotential Height [gpm]:tropopause:anl:
451:239210725:d=2020091500:HGT Geopotential Height [gpm]:max wind:anl:
480:264357652:d=2020091500:HGT Geopotential Height [gpm]:0C isotherm:anl:
482:266204803:d=2020091500:HGT Geopotential Height [gpm]:highest tropospheric freezing level:anl:
511:286486864:d=2020091500:HGT Geopotential Height [gpm]:PV=2e-06 (Km^2/kg/s) surface:anl:
517:290663132:d=2020091500:HGT Geopotential Height [gpm]:PV=-2e-06 (Km^2/kg/s) surface:anl:
as reported here
https://rda.ucar.edu/datasets/ds083.3/index.html#metadata/detailed.html?_do=y
Click to expand...
I want to extract the GHT from the metgrid files because it is already interpolated on the model grid.
The command
Code: 
ncdump -h met_em_d01*****
output states that
Code: 
num_metgrid_levels = 34
float GHT(Time, num_metgrid_levels, south_north, west_east)
So the question is: the 34 levels start from 1000mb to 0.4 mb?
If yes, to extract the GHT500mb I issue the command:
Code: 
ncks -v GHT -d num_metgrid_levels, 12  met_em_d01***** -o out.nc
I'm not sure that 12 (the 13th element of the dimension num_metgrid_levels) is the right level because I find values in the range 4800-5500m.
Thank you
 
Hi,
in met_em file, the first level is always the surface level, and the data then goes up from 1000, 950, 925, 900, 875, ...
You should extract data at level 13, which corresponds to 500 hPa
 
Dear ming,
very helpful, Thank you very much.
So, I will issue the following command:
Code: 
ncks -v GHT -d num_metgrid_levels, 13  met_em_d01***** -o out.nc
 
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