Statistical Analysis of Trend and Change Point in Surface Air Temperature Time Series for Midnapore Weather Observatory, West Bengal, India

This research article aims to detect the short term as well as long term significant changes in the surface air temperature time series for Midnapore Weather observation station, West Bengal, India. The temperature time series data has been collected from Indian Meteorological station, Kolkata, for the period from 1941-2010. Fluctuations and trends of annual mean temperature, annual mean maximum temperature and annual mean minimum temperature time series were statistically examined. To identify the abrupt change in trend, the cumulative sum chart (CUSUM) and Bootstrapping were employed on the considered data set. The major change point in the annual mean temperature occurred around 2001 at level 1 (Confidence level 100%). On the other hand, the annual mean maximum temperature and annual mean minimum temperatures have level 1 change points in 2001 and 1969 respectively. The results show that, one can be 100% confident that the annual mean maximum temperature significantly changed between 1998 and 2001. Similarly, annual mean minimum temperature changed between 1963 and 1971 as a confidence level of 98%. Before the change in 2001, annual mean temperature was 27.11°C; while after the level 1 change the temperature becomes 25.1°C. The mean of annual maximum temperature for the period from 1941-2010 has been 34.017°C which reduced to 30.25°C for rest of the period in consideration. For the annual mean minimum temperature, the time series can be divided into two segment taking 1968 as the last point of the first segment for which the average value is 22.38°C, while the second segment, the average value is 18.077°C. The analysis has identified 13 abrupt change points in three temperature time series.