Trend analysis of Climatic Research Unit temperature dataset for Gangotri glacier, India

Abstract

The absence of continuous long term meteorological dataset has led to limited knowledge of glaciers’ response to climate change over Himalayas. This study presents an open source long term temperature dataset Climatic Research Unit (CRU) available since 1901 to study trend analysis of temperature (Tmax, Tmin and Tmean) for Gangotri basin in Himalayas. The study first establishes close agreement between CRU time series data and observed temperature dataset available from National Institute of Hydrology (NIH), Roorkee for a period of 11 years from 2005 to 2015 using standard anomaly, Wilcoxon Signed-Rank (WSR) and correlation tests. The close agreement of CRU with NIH data validate the use of CRU time series to study variation in meteorological parameter for hilly terrain of Himalayas. The second part includes application of different statistical tests such as Mann-Kendall (MK), Sen’s slope and CUSUM technique on CRU data to detect existence of any possible trends and identification of change points in Tmax, Tmin and Tmean on long term scale. On annual scale, significant increasing trends for Tmean and Tmin were observed with no significant trend for Tmax. On seasonal and monthly scale, Tmax showed significant decreasing trend for monsoon season and increasing trend for winters while Tmin show significant increasing trend for all months (except May) and seasons. CUSUM technique identified 8 change points from 3 annual time series with 2 for Tmean (1974 and 1999), 3 each for Tmax (1941, 1975 and 1999) and Tmin (1941, 1965 and 1999) respectively. Overall, significant increase in Tmin with no significant trend for Tmax has been identified over the study area.