The regional and the seasonal variability of extreme precipitation trends in Pakistan

Abstract

The variability of spatial and temporal trends in extreme precipitation indices and the trend directions were studied for the meteorological seasons of 1950 to 2010. A daily precipitation dataset from 15 weather stations in Pakistan was used. Seven indices were chosen: total precipitation from events ≥ 90th, 95th, and 99th percentiles, the number of days with precipitation ≥ 90th, 95th, and 99th percentiles of daily precipitation amounts, and annual dry days. A study investigating temporal changes in the spatial extent of statistically significant extreme precipitation events was performed. Trends were calculated for each of the 30-year moving periods within the 1950–2010 time period using a simple linear regression technique and Kendall’s tau-based slope estimator. A distinct spatial differentiation appeared in the prevailing directional trends between the northern and southwestern parts of the study area. In all seasons, increasing trends in extreme precipitation dominated in northeastern Pakistan, whereas a reducing tendency towards extreme precipitation prevails in the southwestern part of the country.