Observed diurnal temperature range variations and its association with observed cloud cover in northern Pakistan

Spatio-temporal variability in the observed diurnal temperature range (DTR) for the recent 30-year period (1986-2015) is examined from a total of 18 weather stations in Hindukush Karakoram Himalaya region of northern Pakistan (HKNP). The daily maximum and minimum temperature data are used to compute the regional DTR, whereas observed total cloud cover (TCC) is used to assess its possible relationship with regional DTR, both on seasonal and annual basis. The regional mean DTR is 13.27 degrees C on annual basis, with a maximum in autumn (14.63 degrees C) and minimum in winter (11.81 degrees C). On annual basis, the regional DTR has increased significantly at a rate of .34 degrees C/decade, during the 30-year study period at p .05, based on Mann-Kendall test. On seasonal basis, the DTR displays an increasing trend in all four seasons with largest significant increase in the winter season at a rate of .32 degrees C/decade. The DTR is positively correlated with maximum temperature of the region on seasonal and annual basis. Strong negative correlation is found between the DTR and observed TCC in all seasons, indicating that variability in TCC has an impact on the variation of DTR in this region. The statistically significant increasing DTR trend along with statistically significant decreasing trend of TCC in spring season suggests an early melt of snow and ice covers in the region, consequently changing the hydrological cycle of the region that demands a better water resource management in the HKNP.