Use of Indices on Daily Timescales to Study Changes in Extreme Precipitation Across Nepal Over 40 Years (1976–2015).

This paper presents a comprehensive picture of extreme precipitation across Nepal from 1976 to 2015 based on high‐quality daily precipitation observations from 28 precipitation stations spatially distributed across the country. We computed 11 extreme precipitation indices. The selected indices allow the analysis of extreme events (such as flood/inundation) related to heavy precipitation and evaluate the linkage with indications of agricultural production and drought (such as consecutive dry and wet days). Using a simple daily intensity index (SDII) and the number of days with daily precipitation ≥10 mm (R10), along with the total amount of annual precipitation (PRCPTOT), we summarized the distribution of the wet periods of the year at different locations. We divided the study period into two halves (T1: 1976–1995 and T2: 1996–2015) to examine the temporal mean, trends, and their shift. We emphasized the changes in those indices between these two periods across the country. Our results show that although the amount of precipitation (in terms of PRCPTOT and SDII) did not change significantly between the two periods (i.e., T1 and T2), there exists a clearly increasing trend of extreme precipitation indices in T2 compared to T1. In addition, the consecutive dry days show the rising tendency of elongated dry spells that can adversely affect plant/crop growth in the future. Our study recommends the need for effective management of both precipitation extremes (i.e., drier and wetter), for instance, by introducing irrigation facilities and flood mitigation measures. Plain Language Summary: We computed different precipitation indices using daily data from 28 precipitation stations spatially distributed across Nepal to obtain a clear picture of extreme precipitation from 1976 to 2015. We divided the study period into two halves of 20 years each. This study emphasizes the changes in magnitudes and trends of extreme precipitation between the two periods. Overall, we find that heavy precipitation indices increased significantly in the later period. Notably, dry spells (i.e., no rainfall) for consecutive days showed a remarkably increasing trend. Our results indicate the need for mitigation of this extreme precipitation to prevent both floods and drought. Key Points: We divide the study period (1976–2015) into two halves to analyze precipitation patterns and their shiftWe emphasize changes in the precipitation indices across the country between the two periodsWe find a clearly increasing trend of extreme precipitation indices in the recent period when compared to the earlier one [ABSTRACT FROM AUTHOR]