Climatic classification: the semi-arid tropics and its environment – a review

Abstract

This paper analyses the advantages and limitations in using the Troll, Hargreaves and modified Thornthwaite approaches for the demarcation of the semi-arid tropics. Data from India, Africa, Brazil, Australia and Thailand, were used for the comparison of these three methods. The modified Thornthwaite approach provided the most relevant agriculturally oriented demarcation of the semi-arid tropics. This method is not only simple, but uses input data that are available for a global network of stations, Using this method the semi-arid tropics includes major dryland or rainfed agricultural zones with annual rainfall varying from about 500 to 1,250 mm. Major dryland crops are pearl millet, sorghum, pigeonpea and groundnut. This paper also presents the brief description of climate, soils and farming systems of the semi-and tropics.