Spatiotemporal Analysis of Climatic Extremes over the Upper Indus Basin, Pakistan

The Hindukush-Karakoram-Himalayan (HKH) ranges and their massive cryosphere extend over the Upper Indus Basin (UIB) and are prone to incapacitated water supply due to the proclivity of globally increased temperature. Due to excessive carbon emissions, frequent incursions including extreme climatic events, are likely to happen sooner than expected on a regional scale due to recent climate change. The present study examined the variability of climatic extremes (18 indices) during 1971 to2018 over the UIB. The Mann-Kendall (MK) test and Sen's methods were applied for statistical analysis as the former deals with the magnitude of trends while the direction of observed trends was identified by the latter in climatological time-series data. The frequency and intensity of summer days (SU25 > 25 degrees C/year) at 13 out of 27 stations significantly increased, particularly in lower regions. The same warming proclivity was dominant in tropical nights (TR20 > 20 degrees C/year) at 20 stations including Astore, Bunji, Gilgit, Gupis, Murree and Skardu. Similarly, significant increases were observed in extremes of annual precipitation in western and high northern areas; however, significantly, the highest drops in R25 and R5day were exhibited in Chitral at the rates of 13 and 29 days, respectively. These findings tend to support the accelerated summer warming and a rather stable winter warming while stable winter warming showed that overall the UIB seems to be more sensitive towards warming.