Recent decadal variability of daily observed temperatures in Hindukush, Karakoram and Himalaya region in northern Pakistan

Spatiotemporal variability in the observed daily temperatures for a recent 30-year period (1986-2015) is examined from a total of 18 different weather stations in the Hindukush, Karakoram and Himalaya region in northern Pakistan (HKNP) by employing probability distribution functions (PDFs) on annual and seasonal basis. The region is a hub of glaciers and perennial snow cover which fulfills a large fraction of Pakistan's water demand for irrigation, power generation and for drinking purposes. The temperature-based PDFs show a significant mean decadal warming of 0.45 degrees C, 0.03 degrees C, and 0.25 degrees C, in the maximum (Tmax), minimum (Tmin) and mean temperature (Tmean) of the region, on annual basis, respectively. However, the observed river discharges-based PDFs of the region show a mean negative decadal shift of - 40.15m(3)/s on annual basis. The negative decadal shift in river discharge in warm climate is discussed in terms of percentile-based analysis which quantifies temperature changes for each percentile. The results revealed that the decadal changes in Tmin percentiles are more correlated with river discharge than decadal changes in Tmax and Tmean percentiles, on annual basis. The seasonal analysis showed a significant positive decadal shift of 1.93 degrees C for Tmax in spring season, whereas winter season showed a significant negative decadal shift of -0.56 degrees C in Tmin of the HKNP region, from first decade (1986-1995) to third decade (2006-2015), respectively. The rest of seasons (i.e., summer and autumn) displayed high variability in the Tmax, Tmin and Tmean in the HKNP region. A high observed (non-parametric) correlation between the observed cloud cover and temperatures of the region indicates that changes in regional cloud cover may influence the regional temperatures. This work highlights the importance of recent temperature variations in the HKNP and its connection with the downstream river discharge of the region in changing climate of northern Pakistan.