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STAR Satellite Rainfall Estimates

Compressed Digital Data In GrADS Format

The real time, 4 Km by 4 Km resolution rainfall rate estimation data on digital format are available from the NOAA/NESDIS/ORA anonymous FTP address. The file names have the form A20053141600.Z : a one letter identifier, followed by the four-digit year, three digit Julian day, and four digits for the hour and the minutes in UTC. The time given is the end of the time range; a 6-hour estimate at 1815 UTC shows the total estimated rainfall from 1215 to 1815 UTC There are two sets of files available: one for South America, and one for Mexico, Central America, and the Caribbean. The first letter of the name defines the sector and time span of image:

GrADS File Naming Conventions: File Prefixes
Data Product South America File Prefix Central America File Prefix
1 hour estimates A K
3 hour estimates B L
6 hour estimates C M
24 hour (12-12) D N
24 hour (0-0) N/A Z

The files are available, under normal conditions, approximately 30 minutes after the image time and are produced twice an hour. The files are compressed and have an original size of 8.768.268 bytes (South America) or 3.905.952 (Central). They can be uncompressed using the Unix command "uncompress *.Z".

You can schedule your machine to automatically grab the files using an anonymous ftp call to ftp.star.nesdis.noaa.gov. The files are in the directory /pub/smcd/emb/f_f/hydroest/grads, in subdirectories southamerica and centralamerica. The 24-hour totals are kept online for about a year; the shorter times are restricted to the latest 24 files.

The files were generated from images remaped to Mercator projection. The top left corner has lat/lon = 13:00:00/82:00:00 and the lower right corner has lat/lon = -45:00:00/30:00:00. I have used the GrADS-1.7Beta6 version to display the data and below is an example of the GRADS control files (autosa.ctl) needed to display the images:

GrADS Control Files For Image Display
South American Version Central American Version
DSET A20053141609
UNDEF -1.0
TITLE Rain Rate Estimates (mm)
XDEF 1359 LINEAR 278 0.0382513
YDEF 1613 LINEAR -45 0.0359477
ZDEF 01 LEVELS 1
TDEF 1 LINEAR 16:09Z10NOV2005 1hr
VARS 1
rr 0 99 Goes Data
ENDVARS
DSET K20053141609
UNDEF -1.0
TITLE Rain Rate Estimates (mm)
XDEF 1464 LINEAR 245 0.0382513
YDEF 667 LINEAR 6 0.0359477
ZDEF 01 LEVELS 1
TDEF 1 LINEAR 16:09Z10NOV2005 1hr
VARS 1
rr 0 99 Goes Data
ENDVARS

In the South American listing, 1359 is the number of columns and 1613 is the number of lines. 278 is the longitude of the left side (82 W, counted from east to west); -45 is the latitude of the bottom edge. 0.0382513 and 0.0359477 are the degree step size on the east-west and north-south directions respectively. To display the images in GRADS format use the the program below:

'open autosa.ctl'
'set gxout shaded'
'd rr'
'run cbar.gs'

Note:

This is an experimental product and has neither been calibrated or validated for South America or Central America and its use is at the user's own discretion.