Observed changes in precipitation in China-Pakistan economic corridor during 1980-2016

Changes in precipitation have been widely considered as a critical indicator of climate change. This is of prime importance to assess the strength and magnitude of these changes on regional and local scale. To document the observed changes in precipitation over China-Pakistan Economic Corridor (CPEC), the current study was conducted with monthly precipitation data from 53 meteorological stations across the CPEC. The non-parametric Mann-Kendall (MK), Sen's Slope (SS) estimator, and Sequential Mann-Kendall (SQMK) tests were used to assess the trends in precipitation data during 1980 to 2016. The results indicated that winter and post-monsoon precipitation were decreased at the rates of -0.26 and -0.02 mm per year, respectively. Monsoon, pre-monsoon and annual precipitation increased at the rates of 0.14, 0.13, and 0.02 mm per year, respectively. The spatial distribution of trends for seasonal and annual precipitation over different sub-climatic regions indicated that the trend is dynamic and varies from station to station. The station with SS and MK tests for the winter precipitation data showed an increasing (decreasing) trends at 14 (39) stations and only 1 (7) are significant at 0.05 level, respectively. The pre-monsoon, monsoon, post-monsoon, and annual precipitation indicated a positive (negative) trends over 40 (13), 31 (22), and 35 (18), 28 (25) stations with 3 (1), 5 (2), 2, 6 (7) significant stations at significance level of 0.05, respectively. The maximum positive and negative trends were detected at Parachinar (1.82 mm/year) and Dir (similar to 1.86 mm/year) stations in pre-monsoon and winter precipitation, respectively. The mutations in temporal trends of seasonal and annual precipitation are very complex and dynamic during the study period. In winter, the rapid downward shifts were observed in 1984 and 1995. The mutations in pre-monsoon precipitation occurred after 1996s with a rapid upward/downward shift in 1997/2000. The monsoon precipitation shows a rapid decreasing shift since 1989 and an abrupt upward change in 2011. In post-monsoon precipitation, the rapid downward and upward changes were detected in 1989 and 1999, respectively. The mutations in annual precipitation were found in the first decade of the study period with a steep increase in 1982 and abrupt decrease in 1986. With respect to elevation dependency, the trend of long-term precipitation fluctuates and show a significant increasing trend in elevation zones of <= 500 m and >= 1500 m, while the trend decreases in 500-1000 m and 1000-1500 m elevation zones. Moreover, the winter, monsoon and annual precipitation shows negative correlation with elevation, while the pre-monsoon and post-monsoon precipitation show positive correlation with elevation. The findings of this study will help to address the problems of climate change and hydro-meteorological disasters in the regions. Further studies should focus on the climatic drivers of these changes in the regions.