Description of CPC/Famine Early Warning System Daily Estimates

Original documentation can be found in the ARC2_readme.txt file at

For more documentation, see: Africa Rainfall Climatology Version 2 PDF Document and the following web page:

The following information is excerpted from the "readme" file referred to above:

# This is the readme file for the Africa Rainfall Climatology (ARC) available
#  on the Climate Prediction Center's ftp server.
# Modified:  March, 2012


This data is a result of a project to create a satellite-estimated precipitation
climatology over the Africa domain.  This climatology has been created to 
compliment the daily operational rainfall estimate product (RFE) in order to generate
anomaly fields over Africa over various timescales.  

In contrast to the operational daily rainfall estimate (RFE), where inputs include
SSMI, AMSUB, half-hourly GPI, and GTS data, the climatology method (ARC)
uses only 3-hourly GPI and GTS data, exclusively.  This is due to the absence of
microwave-derved estimates over a long-term historical record, and the large amount of data 
which makes up the operational half-hourly GPI input.  As such, the ARC algorithm itself 
has been slightly modified in order to maintain a homogeneous and stable climate data record. 

GTS rain gauge data used in both static and daily-updating climatology products
is of the same source, though inputs used to create GPI estimates differ slightly
in source.  For creation of the climatological GPI, 3-hourly Meteosat data was
obtained directly from Eumetsat's archived data group, while daily-updating products
use 3-hourly data pulled from NOAA's Meteosat data feed.

Data resolution and specifications of the ARC dataset are identical to that of the RFE.
Files consist of binary-formated grids at a 0.1 degree resolution 
and one day's temporal domain is from 0600 GMT through 0600 GMT.  
Spatial extent of all estimates spans 20.0W-55.0E and 40.0S-40.0N.

As of March, 2012. The ARC dataset has been extended back to 1983 and is labeled as ARC2. 
The former ARC dataset (ARC1) from 1995-present is listed under:

This data will eventually be removed. Please see following .pdf and weblink for ARC documentation:


For - 
NAMING CONVENTION:  "daily_clim.bin.YYYYMMDD.gz"
  (where: YYYY is 4-digit year, MM is 2-digit month, DD is 2-digit day)

For - 
  (where: YYYY is 4-digit year, MM is 2-digit month, DD is 2-digit day, K is dekad)

Data files are written in binary data format and consist of one record (one array)
of floating point rainfall estimates in mm (after unzipping).  Each array equals 
751*801 elements, pertaining to 751 pixels in the x direction, and 801 pixels in 
the y direction.  After reshaping to a 0.1 degree grid, this will yield a spatial 
domain spanning -40S to 40N in latitude, and -20W to 55E in longitude encompassing the 
Africa continent.  Missing data is denoted as -999.0.

Sample fortran programs are also provided in the respective ARC directories to convert
binary data to ascii (.txt) format.  The format of the ascii output will list each gridded 
rainfall estimate. 

This document will be updated as the need arises.  For questions or comments, or to 
report errors and/or inconsistencies with this data, please contact: or 301-763-8000 ext 7513.