In this paper we derive climatic clusters of the Indian region using data on monthly mean profiles of the precipitation, the moisture index (defined as the ratio of precipitation and potential evapotranspiration) and of the minimum temperature. The delineation of regions over which the patterns of profiles of important climatic factors such as precipitation are similar is necessary for the determination of meteorological zones over which prediction can be made as well as for understanding the distribution of vegetation cover. The latter has been the major aim of the studies of climatic classification. In the traditional approach to this problem, the meteorological stations in the region are assigned to predetermined categories such as arid, semi-arid etc. on the basis of the values of the climatic factors (or of the bulk parameters derived therefrom) characterizing these stations.
Here the variation of the climatic patterns over the Indian region has been analysed to obtain climatic clusters, which represent natural grouping of the patterns and hence of the meteorological stations at which they occur, as well as the climatic boundaries separating these clusters. This analysis is facilitated by an initial reduction of dimensionality in the description of the patterns achieved by using principal component analysis. Sixteen clusters of the mean monthly profiles of the moisture index have been obtained. It is found that there is a close correspondence between these clusters and the distribution of the vegetation types in the country.