This paper
aims to detect the short-term as well as long-term change point in the surface air
temperature time series for Asansol weather observation station, West Bengal, India.
Temperature data for the period from 1941 to 2010 of the said weather observatory
have been collected from Indian Meteorological Department, Kolkata. Variations and
trends of annual mean temperature, annual mean maximum temperature and annual minimum
temperature time series were examined. The cumulative sum charts (CUSUM) and bootstrapping
were used for the detection of abrupt changes in the time series data set. Statistically
significant abrupt changes and trends have been detected. The major change point
in the annual mean temperatures occurred around 1986 (0.57°C) at the period of 25
years in the long-term regional scale. On the other side, the annual mean maximum
and annual mean minimum temperatures have distinct change points at level 1. There
are abrupt changes in the year 1961 (Confidence interval 1961, 1963) for the annual
mean maximum and 1994 (Confidence interval 1993, 1996) for the annual mean minimum
temperatures at a confidence level of 100% and 98%, respectively. Before the change,
the annual mean maximum and annual mean minimum temperatures were 30.90°C and 23.99°C,
respectively, while after the change, the temperatures became 33.93°C and 24.84°C,
respectively. Over the entire period of consideration (1941-2010), 11 forward and
backward changes were found in total. Out of 11, there are 3 changes (1961, 1986
and 2001) in annual mean temperatures, 4 changes (1957, 1961, 1980 and 1994) in
annual mean maximum temperatures, and rest 4 changes (1968, 1981, 1994 and 2001)
are associated with annual mean minimum temperature data set.