Long Term Trends in Mean Annual Surface, Mean Annual Maximum and Mean Annual Minimum Air Temperatures for Kolkata during 1941-2010

Abstract

This study examines the changes in annual mean (minimum and maximum) temperatures for Kolkata weather observatory during 1941-2010. The analysis focus on the air temperature time series records at Alipore station (Kolkata) of Indian Meteorological Department (IMD). Variation and trend in annual mean temperature, annual mean maximum temperature and annual mean minimum temperature time series were statistically examined using CUSUM chart and bootstrapping techniques to identify the abrupt change in the considered data set. The major change (level 1) in the annual mean temperature occurred around 2001 with a rise of 1.417 °C. The numbers of change points in annual mean maximum and annual mean minimum temperature time series are detected at different levels but not at the level 1. Over the period under consideration (1941-2010), 4 forward and backward abrupt changes (1961, 1963, 1971 and 1991) are noticed in annual mean maximum temperatures, while 6 changes (1961,1964,1967,1974,1985 and 2003) are associated with the annual mean minimum temperature data set.