Climatic classification of semi-arid tropics in relation to farming systems research

The International Crops Research Institute for the Semi-Arid Tropics has a mandate to increase and stabilize the agricultural production of these areas. The region is characterised by a highly variablelow seasonal rainfall. A number of generalized climatic classification approaches have been reviewed; of these, the approach suggested by Troll to distinguish climates is important. The dry semi-arid tropics need to be mapped on the basis of the large volume of rainfall and evaporation data that is currently available. This paper points out that agroclimatic classification of the semi-arid tropics aims at addressing specific problems like risk to crops/cropping patterns, likelihood of intra- and inter-seasonal droughts, and adequacy of soil moisture in the seeding zone for dry seeding. The selection of criteria for each classification should be based on empirically derived parameter