Persistence in daily and 5-day summer monsoon rainfall over India

Abstract

Persistence in daily rainfall occurrence during the peak summer monsoon months of July–August has been studied for 22 stations, widely spread over the country. The logarithmic, Markov chain order 1 and 2 and modified logarithmic models are fitted to the runs of wet and dry days to examine the nature of persistence and the fitness tested byX 2 tests. Markov chain order 2 (modified logarithmic model) fits to the runs of dry spells (wet spells) better than the other models. The logarithmic model is found to be a poor fit for both types of spells. Persistence in daily and 5-day precipitation amounts and in daily expected areal coverage of precipitation is examined by computing auto-correlation coefficients for various lags. Persistence in 5-day precipitation amount and in 5-day expected areal coverage of precipitation is also examined by constructing 3 × 3 contingency tables. All these results show that persistence is more prominently exhibited in certain parts of central and western India.