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RFE (Rainfall Estimate)

Continental Africa

RFE (Rainfall Estimate)

Dekadal Period

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Available Tools


The GeoWRSI is a geo-spatial, stand-alone implementation of the Water Requirements Satisfaction Index (GeoWRSI), as it is implemented by the USGS for the FEWSNET Activity. The program runs a crop-specific water balance model for a selected region in the world, using raster data inputs. The program produces a range of outputs which can either be used qualitatively to help assess and monitor crop conditions during the crop growing season, or can be regressed with yields to produce yield estimation models and yield estimates. Other tools are available to post-process the GeoWRSI outputs so that they can be used in yield estimation models.


The GeoCLIM is a spatial analysis tool designed for climatological analysis of historical rainfall and temperature data. The GeoCLIM provides non-scientists with an array of accessible analysis tools for climate-smart agricultural development. These user friendly tools can be used to obtain and analyze climate data, blend station data with satellite data to create more accurate datasets, analyze seasonal trends and/or historical climate data, create visual representations of climate data, create scripts (batch files) to quickly and efficiently analyze similar “batches” of climate data, view and/or edit shapefiles and raster files, and extract statistics from raster datasets to create time series.


The Early Warning eXplorer (EWX) software is an interactive web-based mapping tool that allows users to visualize continental-scale rainfall estimate (RFE), land surface temperature (LST) and normalized difference vegetation index (NDVI) data and anomalies at varied time steps and review time series analyses.

EWX Lite

The Early Warning eXplorer (EWX) Lite software is an interactive web-based mapping tool that allows users to visualize time series of rainfall, NDVI, evapotranspiration, land surface temperature and snow water volume, where applicable. The EWX Lite allows users to access the same time series database that drives the standard EWX without having to load raster imagery which can inhibit performance in areas with poor internet connectivity.

Product Documentation

Dekadal (10-day) Rainfall Estimate (RFE)

RFE data background:

As of January 1, 2001, RFE version 2.0 has been implemented by NOAA's Climate Prediction Center. Created by Ping-Ping Xie, this replaces RFE 1.0, the previous rainfall estimation algorithm that was operational from 1995 through 2000 (Herman et al., 1997). RFE 1.0 used an interpolation method to combine Meteosat and Global Telecommunication System (GTS) data, and included warm cloud information for the dekadal estimates. RFE 2.0 uses additional techniques to better estimate precipitation while continuing the use of cold cloud duration, or CCD (derived from cloud top temperature), and station rainfall data. Meteosat 7 geostationary satellite infrared data are acquired in 30-minute intervals, and areas depicting cloud top temperatures of less than 235K are used to estimate convective rainfall. WMO GTS data from ~1000 stations provide station rain gauge totals, and are taken to be the true rainfall within 15-km radii of each station. Two new satellite rainfall estimation instruments are incorporated into RFE 2.0, namely, the Special Sensor Microwave/Imager (SSM/I) on board Defense Meteorological Satellite Program satellites, and the Advanced Microwave Sounding Unit (AMSU) on board NOAA satellites. SSM/I estimates are acquired at 6-hour intervals, while AMSU rainfall estimates are available every 12 hours. RFE 2.0 obtains the final daily rainfall estimation using a two part merging process. All satellite data are first combined using the maximum likelihood estimation method, then GTS station data are used to remove bias. For more information on the FEWS RFE algorithm, please refer to the RFE 2.0 documents at   Note: Scroll to the bottom of the page.

The daily data are in geographic coordinates. The daily totals are summed to produce the dekadal totals and the dekadal totals are then projected to the coordinate system described below.

Dekadal RFE data characteristics:

Source: NOAA-CPC
Time step: 10-day (dekadal)
Resolution: 8km
Projection: Albers equal area conic
File Format: Windisp image, byte (8 bit); Generic BIL, "Integer" (16 bit).

Africa Continental Details:

     Coordinates for corners:

     Lower left lat : -42.243 deg
     Lower left lon : -23.490 deg
     Upper left lat : 43.711 deg
     Upper left lon : -24.600 deg
     Lower right lat : -42.242 deg
     Lower right lon : 63.414 deg
     Upper right lat : 43.712 deg
     Upper right lon : 64.523 deg

     Image size : 1152 rows x 1152 cols
     Center lat,lon : 1.000000, 20.000000
     Pixel size h x w : 8.000000 km x 8.000000 km
     Origin of latitudes : 1.000000 deg
     Central meridian : 20.000000 deg
     First std parallel : -19.000000 deg
     Second std parallel : 21.000000 deg
     Projection = ALBERS Conical Equal-area projection uses the clarke 1866 spheroid


Xie, P. and P. A. Arkin, 1997. A 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bulletin of the American Meteorological Society 78(11): 2539-58"