A Study on Spatial and Temporal Distribution of Rainfall in Province Number 3, Nepal

Abstract

Daily observed precipitation data of 23 stations for the period of 1980-2015 is used in the study of spatial and temporal distribution of rainfall in Province 3 of Nepal. The study is basically focused on the study of space time variation and principal component analysis of rainfall. About 80.6% of annual rainfall is covered by monsoon rainfall so both spatial and temporal distribution of annual rainfall is proportionate with monsoon rainfall (JJAS). Highest rainfall pocket area is observed in northeastern part of Province in the periphery of Gumthang, Sindhupalchok with rainfall of 3828 mm while lowest rainfall is observed in Tamachit, Rasuwa with 720 mm. Temporally rainfall is high in 1999 with rain 2399.4 mm and low in 1992 with rain 1508 mm. July is highest rain month and November is lowest. Seasonally, increasing trend of rainfall is seen in Pre monsoon while decreasing trend is seen in Monsoon, Post monsoon and winter. On decadal rainfall analysis it is obtained highest rainfall in third decade (2000-2009) and lowest in last decade (2010-2015). Analysis of rainfall shows average annual rainfall in lowland is 1883.8 mm and highland is 1959.6 mm. The correlation coefficient between rainfall in highland and lowland is 0.79. In most of the La Nina year there is increased rainfall and El Nino year the rainfall is decreased. So, we can conclude that there is some influence of large scale atmospheric phenomena like ENSO. First component (PCA1) of Principal component analysis which covers largest information of space time variation of rainfall shows that pre monsoon precipitation pattern is highly concentrated in central part of the Province while monsoon is concentrated in southern part of the Province. Similarly, Post monsoon precipitation pattern is concentrated in central part of the Province while winter precipitation pattern is concentrated over both the central as well as southwestern part of the Province.