Trends in temperature, diurnal temperature range and sunshine duration in Northeast India

Trends in maximum (T-max), minimum (T-min) and mean (T-mean) temperatures; diurnal temperature range (DTR = T-max - T-min); and sunshine duration at eight sites in Northeast (NE) India were investigated. Three sites observed decreasing trends in DTR corresponding to annual, seasonal (pre-monsoon and monsoon) and monthly (September) time scales. On the other hand, DTR increases were also observed at other three sites in monsoon and post-monsoon seasons as well as in the months of June, October and December. The sites showing DTR decreases (increases) witnessed either increasing trends in T-min (T-max) or decreasing trends in T-max (T-min), with T-max (T-min) showing either no trend or increasing at a smaller rate than T-min (T-max). Temperature remained practically trendless in winter and pre-monsoon seasons over NE India. However, temperature increases were observed in monsoon and post-monsoon seasons. Decreasing trends in sunshine duration were observed mainly on annual, seasonal (winter and pre-monsoon) and monthly (January, February and March) time scales. Concomitant decreases in sunshine duration may be one of the potential causes of the observed DTR decreases over NE India. Copyright (C) 2010 Royal Meteorological Society