A Comparative Assessment of Temperature Data from Different Sources for Dehradun, Uttarakhand, India

A comparative study of extreme temperature parameters from different sources is carried out by examining standardized anomalies, trends, correlation, and equivalence of datasets. Maximum temperature (Tmax) and minimum temperature (Tmin) for Dehradun, from two different sources such as computed and gridded data from Climatic Research Unit (CRU) and observed data from India Meteorological Department (IMD) are used for 1901-2012. The CRU data are compared initially with IMD, by graphical assessment of standardized anomalies. Subsequently, change points are identified by using Cumulative Sum (CUSUM)-chart technique for trend analysis. The magnitude and significance of trends are determined by applying Sen's slope test, and on the basis of these, trends are compared. Further, correlation analysis is carried out and datasets are tested for equivalence by using Wilcoxon-Mann-Whitney test. The result shows that annual standardized anomalies of CRU data follow the pattern of annual standardized anomalies of IMD data. The CRU data exhibit similar trends and are well correlated with IMD dataset. Moreover, CRU anomaly data are identical with IMD anomaly data in the recent decades. High resolution gridded CRU data have open access and may be more useful due to its spatio-temporal continuity for land areas of the world.