Numerical Classification of the Climate of South and Southeast Asia

Thornthwaite's classification method. The result indicated that the number of climatic types classified on the basis of thermal efficiency, humidity, and seasonal distribution of water surplus or deficiency amounted to 42 for the regions concerned, so that a delineation of climatic regions corresponding to each type was highly difficult. Only a small-scale map with many inclusions could be produced with respect to humidity climatic types, taking seasonal distribution of water surplus or deficiency somewhat into consideration. Besides the difficulty in mapping, problems inherent to the method were also discussed; use of a parameter, i. e., potential evapotranspiration, is the essential feature of Thornthwaite's method, but there is no guarantee for the validity of the parameter when calculated for the tropical climate, as Thornthwaite himself admitted. Recently we examined the applicability of a numerical taxonomic method to the climatic classification of ]apan,2) with an intention to establish climatic regions of the country as a basis of classification of alluvial soils. As noted in this study the numerical method gave readily mappable climatic regions with a fairly good internal coherence, while Thornthwaite's method adopted for the purpose of comparison presented the same difficulty as stated above. In the present paper applicability of the numerical taxonomic method to a classi­ fication of the climate of South and Southeast Asia is tested. Here our intention is again to set up climatic regions as a basis for considering classification of alluvial soils in the rice-growing South and Southeast Asia.