[gradsusr] [EXTERNAL] Negative Longitude of -360 in xdef of ctl file

Blankenship, Clay B. (MSFC-ST11)[USRA] clay.blankenship at nasa.gov
Thu Aug 13 10:41:24 EDT 2020


Try adding or subtracting 360 to the longitudes.  Sometimes I see 0 to 360, sometimes -180 to 180.  (-360 to 0 is new to me.)

_______________________________________________________
Clay Blankenship, USRA Atmospheric Scientist
NASA Short-term Prediction Research and Transition Center (SPoRT)
Marshall Space Flight Center, Huntsville, Alabama



From: gradsusr <gradsusr-bounces at gradsusr.org> on behalf of Raphael Ranieri <raphaelcr93 at hotmail.com>
Reply-To: GrADS Users Forum <gradsusr at gradsusr.org>
Date: Thursday, August 13, 2020 at 7:19 AM
To: "gradsusr at gradsusr.org" <gradsusr at gradsusr.org>
Subject: [EXTERNAL] [gradsusr] Negative Longitude of -360 in xdef of ctl file

Hello All,

I'm trying to use some files of a Brazillian institute of meteorology and I'm facing a problem with the longitude values.

They used grads to create a ctl file that can be accessed in this FTP from the institution:
http://ftp.cptec.inpe.br/modelos/tempo/BAM/TQ0666L064/recortes/regioes/2020/07/29/00/BAM_CO_2020072900.ctl

[cid:image001.png at 01D67155.DD331680]

Here we can see that they are using a linear mapping for xdef with a 0.18 step starting from a longitude of -360 degrees according to GrADs docs:
http://cola.gmu.edu/grads/gadoc/descriptorfile.html#XDEF


Since in our case we need the actual longitude and latitude of a point, when we try to read this file we receive longitudes of 360 for example, which do not correspond to any existing longitude.

We are not using Grads to open the file, we are using pygrib ... to use it in a python program.

Since this ctl file is generated by grads we tought you guys could help.

Do you know why the longitude is starting at -360?

Thanks in advance!

Raphael Ranieri
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