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

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 Cambodia
The heart of the country is the alluvial plain drained by the Mekong river. The Dangrek Mountains form the frontier with Thailand and the Cardamom Mountains and the Elephant Range are in the southwest. About half the land is tropical forest. Cambodias climate is like the rest of Southeast Asia governed by the monsoons. In summer, moisture-laden air, the southwest monsoon, is drawn landward from the Indian Ocean. Heavy rainfall and high humidy prevails from mid-May to October. The flow is reversed during the winter. From November to March the drier and cooler winds from the northeast monsoon bring variable cloudiness and infrequent precipitation. During the rainy season, the Mekong river swells and backs into the Tonle Sap Basin. This may increase the lake almost threefold. The seasonal rise of the Mekong floods the soils around the lake and leaves rich silt when the waters recede.

Rainfall around the Tonle Sap Basin increases with elevation. It is heaviest in the mountains along the coast in the southwest. But this area of greatest rainfall drains mostly to the sea. Only a small quantity goes into the rivers flowing into the basin.

Rice and rubber are traditionally the principal exports of Cambodia. But most of the rubber plantations were out of operation with the onset of the civil war (1970). By the 1990s rubber and rice where again being exported. The fishing industry has also been revived, but some food shortages continue. By the mid 1990s timber had become the largest source of export income.

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