Precipitation trends in Sri Lanka since the 1870s and relationships to El Niño-southern oscillation

The last 130 years of fluctuations in precipitation associated with the Southwest Monsoon (summer monsoon), Northeast Monsoon (winter monsoon), First Intermonsoon, and Second Intermonsoon seasons have been analysed at 15 climate stations in Sri Lanka. Analyses of trends in the interannual seasonal series indicated statistically significant temporal changes in Southwest-Monsoon-related precipitation at five of the stations, with three stations showing enhanced rainfall (total of 100 mm/month over the entire time interval) and two stations a decrease in rainfall with time (total of 150 mm/month). In addition, one station experienced a decrease of both First and Second Intermonsoon rainfall over time (total of 80 mm/month). The stations showing loss of rainfall are confined to higher elevation areas and those exhibiting enhanced rainfall are located in the lowlands in the southwestern sector of Sri Lanka. None of the stations show any significant change in Northeast Monsoon precipitation through time. Most of the stations are shown to have received significantly greater amounts of Second Intermonsoon precipitation during El Niño years. The Second Intermonsoon rainfall is, on average, 70 mm/month greater during El Niño years. However, a few stations show increased Southwest Monsoon precipitation (May to September) during La Niña years. Two stations along the eastern and northern coastal areas receive, on average, between 14 and 20 mm/month more Southwest Monsoon rainfall during La Niña years than during El Niño years. Copyright © 2003 Royal Meteorological Society