Spatial variations and trends in the Indian monsoon rainfall

Abstract

Abstract The spatial and temporal variations of the monsoon rainfall over India have been studied using the subdivisional rainfall data for the years 1871–1988. North‐west India and north peninsular India are found to constitute two homogeneous regions. North‐east India does not constitute a single homogeneous region since the rainfall variations in Bihar and Bengal are somewhat different from those in Assam and the Sub‐Himalayan region. Trends in the monsoon rainfall in different subdivisions and in the whole of India also have been examined. In the monsoon rainfall, decreasing trends during late nineteenth century and again in the 1960s are observed. The latter trend was reversed in the early 1970s. These trends are seen prominently in central and western Indian subdivisions, however, there are major differences in the epochs of changes in the trends in different subdivisions. The decreasing trend observed in the 1960s is still continuing in the central north Indian divisions, while in the adjoining divisions, the reversal took place in the early 1970s.