Identification and analysis of recent temporal temperature trends for Dehradun, Uttarakhand, India

Maximum and minimum temperatures (Tmax and Tmin) are indicators of changes in climate. In this study, observed and gridded Tmax and Tmin data of Dehradun are analyzed for the period 1901–2014. Observed data obtained from India Meteorological Department and National Institute of Hydrology, whereas gridded data from Climatic Research Unit (CRU) were used. Efficacy of elevation-corrected CRU data was checked by cross validation using data of various stations at different elevations. In both the observed and gridded data, major change points were detected using Cumulative Sum chart. For Tmax, change points occur in the years 1974 and 1997, while, for Tmin, in 1959 and 1986. Statistical significance of trends was tested in three sub-periods based on change points using Mann–Kendall (MK) test, Sen’s slope estimator, and linear regression (LR) method. It has been found that both the Tmax and Tmin have a sequence of rising, falling, and rising trends in sub-periods. Out of three different methods used for trend tests, MK and SS have indicated similar results, while LR method has also shown similar results for most of the cases. Root-mean-square error for actual and anomaly time series of CRU data was found to be within one standard deviation of observed data which indicates that the CRU data are very close to the observed data. The trends exhibited by CRU data were also found to be similar to the observed data. Thus, CRU temperature data may be quite useful for various studies in the regions of scarcity of observational data.