20040916: downloading FNEXRAD data by ldm

>From: address@hidden
>Organization: GMU
>Keywords: 200409170126.i8H1QrnJ013028 LDM IDD ldmd.conf pqact.conf ldm-mcidas

Ying,

>I can successfully get NIDS data using LDM, but they are partitioned into
>different areas.

That is correct.  The data in the IDD 'NNEXRAD' datastream are products
from individual NEXRADs.

>How to get the data for the U.S in one image? like the composite
>radar image from FNEXRAD.

You have put your finger on what you need to do:  request the data
products in the FNEXRAD datastream.  Here is an example request line
for the FNEXRAD data:

request FNEXRAD ".*"    the_same_IDD_host_feeding_you_NNEXRAD

>The product can be:
>1 km US National Base Reflectivity
>2 km US National 1-hour Precipitation Totals 
>4 km US National Storm Total Precipitation 
>6 km US National Base Reflectivity   

The 6 km national base reflectivity, 1 km regional base reflectivity,
and 10 km RCM (Radar Coded Message) data are available in the FNEXRAD
feed in two formats:  as grib messages and as PNG-compressed images in
McIDAS AREA format.

The 1 km national base reflectivity, 2 km 1-hour precip totals, and 4
km storm total precip products are available as a PNG-compressed image
in GINI format.

>the lines in my pqact.conf is currently as:
>NEXRAD ^SDUS[2357]. .... ([0-3][0-9])([0-2][0-9])([0-6][0-9]).*/p(...)(...)
>      FILE    -close  data/gempak/nexrad/NIDS/\5/\4/\4_(\1:yyyy)(\1:mm)\1_\2\3
>
>What is the script to get FNEXRAD?

Since the data are in a different datastream, you will need actions for
FNEXRAD data in your pqact.conf file.  Exactly what these actions will
look like will depend on how you want to receive the data.  For
instance, GEMPAK can use the PNG-compressed image files directly; it
does not need the images to be uncompressed first.  McIDAS, on the
other hand, will need the images uncompressed before they can be used.

If you are using GEMPAK, there is still have a choice you need to
make:  whether you want to use the data in grib format, or if you want
to access the data in image format.

So, the question is exactly what is your goal?

The following example pqact.conf actions can be used to use ldm-mcidas
decoders to decode all of the image data in the FNEXRAD datastream:

#########################################################################
# 
# FNEXRAD section
#           

# NEXRCOMP 6 km National BREF mosaic
FNEXRAD ^pnga2area Q5 (RL) (.*) (.*) (.*) (.*) (........) (....)
        PIPE    -close
        pnga2area -vl logs/ldm-mcidas.log
        data/gempak/nexrad/NEXRCOMP/6KN0R-NAT/\4_\6_\7

# NEXRCOMP 1 km Regional BREF mosaic
FNEXRAD ^pnga2area Q5 (RO) (.*) (.*) (.*) (.*) (........) (....)
        PIPE    -close
        pnga2area -vl logs/ldm-mcidas.log
        data/gempak/nexrad/NEXRCOMP/1KN0R-FLT/\4_\6_\7

# NEXRCOMP 10 km National RCM mosaic
FNEXRAD ^pnga2area Q5 (RN) (.*) (.*) (.*) (.*) (........) (....)
        PIPE    -close
        decoders/pnga2area -vl logs/ldm-mcidas.log
        data/gempak/nexrad/NEXRCOMP/10KRCM-NAT/\4_\6_\7

# NEXRAD Level III radar composites in PNG-compressed GINI format
FNEXRAD ^rad/NEXRCOMP/(...)/(...)_(........)_(....)
        PIPE    -close
        pngg2gini -vl logs/ldm-mcidas.log
        data/gempak/nexrad/NEXRCOMP/\1/\2/\2_\3_\4

If you want to use the data in compressed format, or in grib format
(for those being sent as grib messages), you will need different
pqact.conf actions.

Another thing to remember:  if you use the actions above, you will need
to worry about adding actions to your crontab that will scour the data
directories in which the images are being decoded.

>Thanks! 

No worries.

Cheers,

Tom Yoksas
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