Historical temporal variation in precipitation over Western Himalayan Region: 1857-2006

This study has examined the temporal variation in monthly, seasonal & annual precipitation over the Western Himalayan Region (WHR) and the influence of global teleconnections, like the North Atlantic Oscillation (NAO) and Southern Oscillation (SO) Indices on seasonal & annual precipitation. The Mann-Kendall non-parametric test is applied for trend detection and the Pettitt-Mann-Whitney test is used to detect possible shift. Maximum entropy spectral analysis is applied to find the periodicity in annual & seasonal precipitation. The study shows a non-significant decreasing trend in annual precipitation over WHR for the period 1857-2006. However, in seasonal precipitation, a significant decreasing trend is observed in monsoon and a significant increasing trend in post-monsoon season during the same period. The significant decrease in monsoon precipitation may be due to weakening of its teleconnection with NAO as well as SO Indices mainly during last three decades. It is observed that the probable change of year in annual & monsoon precipitation over WHR is 1979. The study also shows significant periodicities of 2.3-2.9 years and of 3.9-4.7 years in annual & seasonal precipitation over WHR.