grbf data vs grb2f data

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Cloudy
Posts: 25
Joined: Tue Mar 02, 2010 12:15 am

grbf data vs grb2f data

Post by Cloudy »

When I using data downloaded from http://nomad1.ncep.noaa.gov/cgi-bin/ftp2u_gfs_dir.sh the KIndex formula work fine, but when I try with data from http://nomads.ncep.noaa.gov/cgi-bin/filter_gfs_hd.pl no work.
The formula I use for KINDEX is:
make2D(getSliceAtLevel(T, 850)) - make2D(getSliceAtLevel(T, 500)) + make2D(getSliceAtLevel(TD,850)) - ( make2D(getSliceAtLevel(T,700)) - make2D(getSliceAtLevel(TD,700)) )-273.16
Any ideas?
Many thanks for help

Cloudy
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jayh
Posts: 415
Joined: Thu Jan 15, 2009 10:34 pm

Re: grbf data vs grb2f data

Post by jayh »

Hi Cloudy-

I did replicate your problem with the grib2 data. I believe it's because the level units in the grb2f file are in Pa, and not in hPa like the grbf file.

I made a KINDEX_grb2f formula like this:

make2D(getSliceAtLevel(T, 85000)) - make2D(getSliceAtLevel(T, 50000)) + make2D(getSliceAtLevel(TD,85000)) - ( make2D(getSliceAtLevel(T,70000)) - make2D(getSliceAtLevel(TD,70000)))-273.16

This formula works with the grb2f data. Try this and if you still encounter problems, let us know.

Thanks, Jay
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Cloudy
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Re: grbf data vs grb2f data

Post by Cloudy »

Hi Jay
Many thanks for your help. I did not know the difference between grbf and grb2f.
There are other differences in units between grbf and grb2f?
The formula works fine, thanks for your time. Cloudy

jayh wrote:Hi Cloudy-

I did replicate your problem with the grib2 data. I believe it's because the level units in the grb2f file are in Pa, and not in hPa like the grbf file.

I made a KINDEX_grb2f formula like this:

make2D(getSliceAtLevel(T, 85000)) - make2D(getSliceAtLevel(T, 50000)) + make2D(getSliceAtLevel(TD,85000)) - ( make2D(getSliceAtLevel(T,70000)) - make2D(getSliceAtLevel(TD,70000)))-273.16

This formula works with the grb2f data. Try this and if you still encounter problems, let us know.

Thanks, Jay
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jayh
Posts: 415
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Re: grbf data vs grb2f data

Post by jayh »

Hi Cloudy-

I would suspect there may be other differences. Looking at the Field Selector and comparing the grib1 and grib2 files, there are some differences in the parameters contained in the files. hPa vs Pa for pressure levels looks to be the biggest difference, but I would check any formula carefully for each file.

Thanks, Jay
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Cloudy
Posts: 25
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Re: grbf data vs grb2f data

Post by Cloudy »

Hi Jay
I will also inform if encounter some difference between grb2 and grb2f
Many thanks
Cloudy
jayh wrote:Hi Cloudy-

I would suspect there may be other differences. Looking at the Field Selector and comparing the grib1 and grib2 files, there are some differences in the parameters contained in the files. hPa vs Pa for pressure levels looks to be the biggest difference, but I would check any formula carefully for each file.

Thanks, Jay
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