Correlation functions of rainfall field and their application in network design in the tropics

The study examines the correlation function of tropical monsoon rainfall on monthly, seasonal and annual time scales and obtains the relationship between this function and the distance. The area selected for study is Vidarbha with a fairly dense network of rain gauges. Vidarbha is a meteorological sub-division of the state of Maharashtra in India. Utilizing the relationship between the correlation function of the rainfall field and the distance, the errors of optimum interpolation of rainfall at a point have been computed by applying the method of optimum interpolation by Gandin (1970). Relationships between the errors of interpolation and distance have been evaluated and from this the maximum spacing allowed between rain gauges for a specified tolerable error in interpolation has been estimated for each of the periods

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

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 Indi