Temporal characteristics of pan evaporation trends under the humid conditions of northeast India

This paper analyses the temporal characteristics of pan evaporation (E-pan) trends by using Mann-Kendall non parametric test and a parametric test under the humid conditions for eleven sites of northeast India. Decreasing E-pan trends have been observed mainly in pre monsoon and monsoon seasons. On examining total rainfall's relationship with E-pan it is observed that almost all sites do not show a concurrent decrease in Epan and an increase in rainfall. Trend analysis of other meteorological parameters indicates decreases in sunshine duration and wind speed in different seasons over most of the sites and an increase in relative humidity over four sites in winter and pre monsoon seasons. The likely causative meteorological parameters of E-pan changes by stepwise regression are also identified. The findings of this study suggest that mainly two parameters i.e. sunshine duration followed by wind speed strongly influenced E-pan changes at various sites from different regions in different seasons. (C) 2008 Elsevier B.V. All rights reserved.