20000915: IDD grib data

>From: Shangyao Nong <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200009151644.e8FGinb06898

>Hi,
>
>I learned that AVN and MRF now have 1.25 degree resolution grib data now. Can
>I get such data from unidata?If I can, how will I need to change file pqact.co
> nf?
>
>Thanks.
>
>Shangyao
>

Shangyao,
AVN has been available on the IDD for ~6 years in the 1.25x1.25 
thinned grib octets (0Z and 12Z runs).

The pattern for this data is
HRS     ^H.[I-P].*

The I through P are the 8 octets, 4 in each hemisphere.

An example of decoding these data using the dcgrib decoder for GEMPAK is:
#
# Global AVN (Spectral) Thinned grids
# Grid octets I-P will be stitched together as a single global grid
#
HRS     ^H.[I-P].*
        PIPE    dcgrib
                -g /home/gempak/NAWIPS-5.4/gempak5.4/tables
                -q "lin,dlat=1.25,dlon=1.25"
                PACK data/gempak/hds/YYYYMMDDHH_thin.gem

The thinned grids can be thickend using dlat and dlon multiples as above.
If you wanted to store the data on a 2.5x5 degree grid for instance, you would 
use:
-q "lin,dlat=2.5,dlon=5.0"

AVN and MRF are also available on many other AWIPS grids through the IDD,
however, only the AVN is on the global 1.25x1.25 grid.

For other AVN and MRF pqact.conf examples, see:
http://www.unidata.ucar.edu/packages/gempak/tutorial/pqact/decoders.tbl

The above file is documented with each of the MRF and AVN projections available.

Steve Chiswell
Unidata User Support