Issue with GRIB data from new ECMWF data server?

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Issue with GRIB data from new ECMWF data server?

Postby Andrew.Klekociuk » November 13th, 2013, 3:18 am

Hi. I have been sucessfully using the PC version of HYSPLIT to convert ERA-Interim 1.5 degree gridded data downloaded from http://data-portal.ecmwf.int/data/d/interim_daily/ into the ARL format using the Meteorology>Convert to ARL>ECMWF ERA menu option. That's all nice!

However I am having trouble converting 0.75 degree resolution data dowloaded from the new server at http://apps.ecmwf.int/datasets/data/interim_full_daily/. Now that the higher resolution data is available, I want to see if this provides any advantages over the 1.5 degree data.

GRIB2ARL appears to do the conversion OK in the sense that no error messages are thrown up, but when I use the Check File option (under Meteorology>Display Data) I get error messages like the following:
*ERROR* metset: meteorological data time interval varies
Changed from 360 min to -1080 min
At day/hr 1 0

The listing in Working/checkfile.txt is not what I expect, with incorrect time stamps and fields zeroed from part way through the listing, presumably due to a problem associated with decoding time information from the GRIB files. Trajectory runs using the created ARL data get terminated at the point where the time information in the checkfile.txt listing goes awry. I've been careful to ensure that the 3 files required (invariant, surface and level) have consistent gridding. I've used the ECMWF GRIB-API to examine the files from the new server - they look to be in GRIB1 format, and I can't see an issue with the contents compared with the 1.5 degree data from the old server, except possibly from some extra padding.

I haven't yet used API2ARL to convert the data - I'm wondering if I have to do this (noting there is mention on the board of the ECMWF server moving to GRIB2 format) or if there is some other solution.

Has anyone had a similar issue? Thanks!
Andrew.Klekociuk
 
Posts: 2
Joined: November 13th, 2013, 2:42 am

Re: Issue with GRIB data from new ECMWF data server?

Postby Andrew.Klekociuk » November 13th, 2013, 8:16 pm

OK - I have made some progress.

The issue with data from the new server occurs when forecast fields are selected for the surface data. I can get the conversion to ARL format to work with data from the new server IF when requesting the data I don't select a forecast field (total precipitation) AND I explicitly select the time step as 0 (setting 'select step' to 'all' isn't appropriate even if you don't specify a forecast field such as precipitation).

So in summary, it appears that if you are interested in wet deposition (as I am), there is an issue for ARL conversion of data from the new server.

Another issue I discovered is that the ECMWF batch server (https://software.ecmwf.int/wiki/display ... s+in+batch) will not concatenate forecast and analysis fields - this is unlike the situation for the web interface where you can combine forecast and analysis fields in the one file.

Andrew
Andrew.Klekociuk
 
Posts: 2
Joined: November 13th, 2013, 2:42 am


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