The -lon option prints the value of the grid point
closest to the specified longitude latitude. The latitude-longitude of the grid
point are also printed. If you use the verbose mode, the grid
coordinates (i,j) and the number of the element are also printed.
The -lon option can be repeated to save processing
-sh-2.05b$ wgrib2 eta.t00z.awphys18.grb2 -d 1 -s -lon 249 39 -lon 255 33
1:0:d=2003090300:MSLET:mean sea level:18 hour fcst:lon=249.035,lat=38.9912,val=101685:
-sh-3.00$ wgrib2 rtma.t12z.2dvaranl_ndfd.grb2.c2 -d 1 -v -lon -120 30
In the latter example, the verbose mode has been set and
the inventory includes both the value, location and its
grid coordinates; i.e., the 220037th element in the array and
its coordinates are (72,206). Note that these coordinates
are after the data has been converted into a WE:SN scan order.
Both the i, ix and iy start with a value of one.
-lon LONGITUDE LATITUDE
LONGITUDE = 0 .. 360
LATITUDE = -90 .. 90
If the verbosity is 0, the print out the longitude and
latitude of the nearest grid point as well as the grid value.
If the verbosity is 1 or higher, the prints out the longitude and
latitude of the nearest grid point, the index (i) to the data,
the grid coordinates (ix,iy) as well as the grid point value.
i = 1..number of grid points
ix = 1..nx
iy = 1..ny
$ wgrib2 test.grb2 -s -lon -90 20
1:0:d=2005090200:HGT:1000 mb:60 hour fcst:lon=270,lat=20,val=121.3
2:133907:d=2005090200:HGT:975 mb:60 hour fcst:lon=270,lat=20,val=344.4
3:263511:d=2005090200:HGT:950 mb:60 hour fcst:lon=270,lat=20,val=573
4:389058:d=2005090200:HGT:925 mb:60 hour fcst:lon=270,lat=20,val=806.5
You want extract the values for a 1000 different points.
So you call wgrib2 1000 times and complain that wgrib2 is slow.
Well decoding a jpeg2000 compressed file 1000 times does take time.
It's better to add a 1000 -lon options to the
command line and only decode the file once.
The number of -lon options on a
command line is limited by a compile-time option. Try
running wgrib2 -config and look for the line
"maximum number of arguments on command line:". The current
value is 5000 which allows you 5000 words on the command line. Each
-lon option takes 3 words, so that gives
you about 1600 -lon options you can run
on one line. Of course, limitations such as the maximum line
length or maximum number of continuations may stop you first.
See also: -lola
See also: -config