Correlation structure of daily rainfall over Teesta catchment

Abstract

In many scientific studies, the r-estimates were widely used to know the spatial distribution of daily rainfall in various weather situations.  In this present paper, the  cross - correlation analysis has been performed to understand the  variability of daily rainfall during monsoon months over Teesta catchment. For the purpose of study, ten station's daily rainfall data for the period 1995-2000 has been utilized. The analysis of estimated cross-correlation field entirely for four months of monsoon suggested that the rainfall area during the monsoon months extends up to 60-80 km distance in north-south, northnortheast-southsouthwest and 50 km in the remaining directions. The pattern of daily rainfall can best be represented as intersection of two ellipses, one with major axis in the direction of northnortheast-southsouthwest (75° N-80° N/115° S-100° S) and another with major axis in northnorthwest-southsoutheast (110° N-120° N/70° S-60° S) direction and are  seen traversing in the directions of major uplands. It is also found that the estimated correlation coefficients decreased with distance in all the directions other than in the directions major axes of elliptical patterns of spatial distribution of correlation coefficients and became insignificant beyond 50 km. It is also seen that in hilly regions of the catchment, the moisture feed is blocked further in northnortheast direction (65° N) due to presence of uplands southsouthwest of it.