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Rainfall Variability Analysis of rainfall variability and drought in the 1961-2002 period
Burkina Faso

Global analysis  Annual rainfall | National rainfall index | Global rainfall pattern
Case studies  Burkina Faso | Cambodia | Nepal | Tanzania
Downloads  Images (IDA) | Images (GeoTiff) | Movies (AVI) | Windisp | Quantum GIS

In order to apply the methodology used on the global scale with higher spatial and temporal resolution in the period 1983 to 2002 dekad rainfall grids at a spatial resolution of approx 0.1 degree are computed. Concerning Burkina Faso, 133 rainfall stations have been available for the selected time horizon. In this case interpolation techniques can be applied directly on rainfall station data. The interpolation has been performed with inverse distance and regression methods provided within SEDI (AMS).

For Tanzania, Cambodia and Nepal available stata data was insufficient. So, the generation of the rainfall grids has been achieved through a "downscaling" procedure of global NOAA rainfall grids having a monthly resolution and a spatial resolution of 0.5 degrees. Within this procedure for each of the three countries a "virtual" grid of rainfall stations is constructed with a densitiy and distribution of grid points comparable to the station data in Burkina Faso. After the extraction of the rainfall data for each grid point from the global NOAA rainfall grids, inverse distance and regression methods (SEDI) are used again in order to generate the desired spatial resolution. In coherence with Burkina Faso, most interpolation has been carried-out using the inverse distance technique. Finally, the monthly rainfall grids are converted to dekadal grids using a utility by R. Gommes.

The rainfall maps and the maps presenting the rainfall index for agroecological zones and the first administrative level concerning Burkina Faso and Tanzania are in Hammer-Aitoff projection and all maps concerning Cambodia and Nepal are in Goodes Homolsine projection.

Climatological facts about Burkina Faso
Burkina Faso rank among the driest and most variable countries in Africa. In the north the climate is the Sahelian type. To the south it becomes increasingly affected by the mechanism of the west African Monsoon, which is caused by the differential heating of land and ocean. The southwest summer monsoon flows as a shallow humid layer of surface air, overlain by the primary northeast trade wind, which blows from the Sahara and the Sahel as a deep stream of dry, often dusty air, gernerally known as the harmattan. This mechanism accounts for the relative stability of the countries in the Gulf of Guinea. The monsoon rain belt moves north and reaches the Sahel Belt in May. In September, the season ends, when the rain moves to the south again.

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