Year-in-advance Forecasting of the Indian Monsoon Rainfall

Abstract

The paper starts out by discussing factors which influence the Indian monsoon rainfall—including Northern Hemispheric temperature changes, long-period soli–lunar tides, and the tidelike phenomena associated with the wobble of the Earth relative to its spin-axis. When the effects of these factors on precipitation are quantified and integrated into a thermodynamical–statistical model, long-range climatic forecasts can be made that are better than chance or than predicting ‘normal’ up to two or more years in advance.Climatic changes have had profound effects on the peoples of India through the controlling influence of the monsoon on Indian agriculture. We now have a technological tool, never before available, that might lessen the impact of variations of the monsoon by forecasting these variations one to two years in advance. The two-years-in-advance 1982 monsoon rainfall forecast for June and July, using the same station models that produced the excellent 1981 forecast, indicates that there is a two-to-one chance that the 1982 Indian monsoon rainfall will be less, in general, in June and July, than it was in 1981. The question which we wish to ask the reader is: How can this new technology be used? For example, how can this type of information be used for planning and policy-making in order to ensure less uncertainty about food supplies in the future than in the past?This region cannot depend upon the monsoon to bring plentiful rain every year, and, therefore, it is essential that we should continue to improve our forecasting capability and that others learn to make optimum use of these forecasts.