 |
| | | | | Rainfall Variability | |
| |
|
|
| Burkina Faso
|
 |
|
|
|
|
|
|
|
Burkina Faso |
|
|
|
|
|
|
|
|
|
|
Data
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.
|
|
|
