Problem with points near 180 lon

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kwc780330
Posts: 1
Joined: November 21st, 2017, 1:11 pm
Registered HYSPLIT User: Yes

Problem with points near 180 lon

Post by kwc780330 » November 21st, 2017, 1:18 pm

Hello.

When my trajectories have points near 180 lon (or -180 lon), there are error messages. Here is one example:

Code: Select all

 WARNING main: source point off grid number         1217
 Position:   3.1300001      -180.00999
 Grid Loc:   480.98666       72.173332
 WARNING main: source point off grid number         1218
 Position:   3.1400001      -180.00999
 Grid Loc:   480.98666       72.186668
 WARNING main: source point off grid number         1219
 Position:   3.1400001      -180.00999
 Grid Loc:   480.98666       72.186668
 WARNING main: source point off grid number         1220
 Position:   3.1500001      -180.00999
When starting point has a longitude greater than 179 or so, I also get an error like this:

Code: Select all

 WARNING main: source point off grid number            1
 Position:   3.1400001       179.50000
 Grid Loc:   480.33334       72.186668
How can I fix this problem? I am currently using ARL files converted from ERA-interim 0.75 resolution reanalysis.

If it helps to know, my CFG_ARL files looks like this:

Code: Select all

Model Type:         ECMG
Grid Numb:            99
Vert Coord:            2
Pole Lat:               50.250
Pole Lon:              179.250
Ref Lat:                 0.750
Ref Lon:                 0.750
Grid Size:               0.000
Orientation:             0.000
Cone Angle:              0.000
Sync X Pt:               1.000
Sync Y Pt:               1.000
Sync Lat:              -50.250
Sync Lon:              180.000
Reserved:                0.000
Numb X pt:           480
Numb Y pt:           135
Numb Levels:          31
Level  0:           .00000  4 SHGT U10M V10M T02M
Level  1:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level  2:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level  3:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level  4:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level  5:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level  6:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level  7:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level  8:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level  9:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 10:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 11:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 12:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 13:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 14:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 15:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 16:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 17:           ******  0
Level 18:           ******  0
Level 19:           ******  0
Level 20:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 21:           ******  0
Level 22:           ******  0
Level 23:           ******  0
Level 24:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 25:           ******  0
Level 26:           ******  0
Level 27:           ******  0
Level 28:           ******  0
Level 29:           ******  6 HGTS TEMP UWND VWND WWND RELH
Level 30:           ******  0

barbara.stunder
Posts: 299
Joined: November 9th, 2012, 4:23 pm
Registered HYSPLIT User: Yes

Re: Problem with points near 180 lon

Post by barbara.stunder » November 27th, 2017, 11:09 am

The CFG_ARL file says that the grid point (1,1) is -50.25 deg latitude and 180.0 deg longitude. Is that what you want? Are you running api2arl? Our global lat-lon file has 1,1 at -180 longitude.

Two utility programs that are useful to check a meteorology file are:
chk_file (GUI Meteorology / Display Data / Check File)
showgrid (Meteorology / Display Data / Grid Domain)

Run these to verify the file looks fine.

alicec
Posts: 116
Joined: February 8th, 2016, 12:56 pm
Registered HYSPLIT User: Yes

Re: Problem with points near 180 lon

Post by alicec » November 27th, 2017, 11:53 am

That error is given when your trajectory goes off of your meteorological grid.
Try using the showgrid utility program to create a map of the domain of your meteorological file.
Also please give more information on how you are downloading and converting your ERA-INTERIM files.

I am not able to reproduce the problem with the ERA-INTERIM files that I have.
See my cfg-arl file below which is differing from yours in that the lower left corner of the lat-lon
grid starts at 0 longitude and goes around to 360. (Note that I can also run starting at 259.5 just fine).


Model Type: ECMG
Grid Numb: 99
Vert Coord: 2
Pole Lat: 90.000
Pole Lon: 359.250
Ref Lat: 0.750
Ref Lon: 0.750
Grid Size: 0.000
Orientation: 0.000
Cone Angle: 0.000
Sync X Pt: 1.000
Sync Y Pt: 1.000
Sync Lat: -90.000
Sync Lon: 0.000
Reserved: 0.000
Numb X pt: 480
Numb Y pt: 241
Numb Levels: 38

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