<div dir="ltr"><div dir="ltr">Ivan,<br></div><div dir="ltr"><br></div><div>Not sure if it would account for the difference but when converting from K to C it should be -273.15.</div><div><br></div><div>So in your example:</div><div><br></div><div> 'd tmp2m-273.15' <br></div><div><br></div><div>Brian</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, 23 Aug 2020 at 17:01, <<a href="mailto:gradsusr-request@gradsusr.org">gradsusr-request@gradsusr.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Send gradsusr mailing list submissions to<br>
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Today's Topics:<br>
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1. GrADS and wgrib2 temperatures in disagreement (Ivan Toman)<br>
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Message: 1<br>
Date: Sun, 23 Aug 2020 12:01:51 +0200<br>
From: Ivan Toman <<a href="mailto:ivtoman@inet.hr" target="_blank">ivtoman@inet.hr</a>><br>
To: GrADS Users Forum <<a href="mailto:gradsusr@gradsusr.org" target="_blank">gradsusr@gradsusr.org</a>><br>
Subject: [gradsusr] GrADS and wgrib2 temperatures in disagreement<br>
Message-ID: <<a href="mailto:80efbf07-0e18-4a6f-b073-651ffe3f0cf4@inet.hr" target="_blank">80efbf07-0e18-4a6f-b073-651ffe3f0cf4@inet.hr</a>><br>
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<br>
Hello dear GrADS users,<br>
<br>
I have a problem. If I extract 2m temperature for a single lat/lon point <br>
using GrADS, it is in slight disagreement compared to same record <br>
obtained from grib2 file using wgrib2.<br>
<br>
The difference is usually around 1C but can be larger from time to time. <br>
I'm almost 100% sure I did not overlook anything obvious like selecting <br>
different time or diffrent lat/lon coordinates, but I leave something <br>
like that as a theoretical possibility if there is no better <br>
explanation. Below is an example how I extract temperatures using GrADS. <br>
Grib2 is WRF file, Lambert projection, and ctl/idx files are created <br>
using latest g2ctl and gribmap utilities. I note this because it might <br>
be that projection gets somehow skewed and that GrADS takes data from <br>
incorrect positions. Is that possible at all?<br>
<br>
It seems very important to add that wgrib2 method is in exact agreement <br>
to the tslist output from WRF, so for now I take that one as "correct" <br>
one and GrADS figures as "incorrect".<br>
<br>
Simple extraction method in GrADS:<br>
<br>
'set lat 45.822'<br>
'set lon 16.034'<br>
'set string 1 bl 3 0'<br>
'set t 13'<br>
'd tmp2m-273'<br>
ans = sublin(result,2)<br>
temp = subwrd(ans,4)<br>
<br>
<br>
Is this difference normal/expected? If it is, what's the reason for <br>
that? If not, is there anything else where I could search for user error?<br>
<br>
Thank you,<br>
<br>
Best regards,<br>
<br>
Ivan Toman<br>
<br>
<br>
<br>
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End of gradsusr Digest, Vol 126, Issue 20<br>
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</blockquote></div></div>