Spatial and Temporal Patterns in Observed Extreme Precipitation Change Over Northern Part of the Korean Peninsula

AbstractThe present study aims to detect the variation of precipitation extreme events in the northern part of the Korean Peninsula during 1961–2020, as well as to investigate its possible causes, based on daily precipitation data from 37 representative stations. Nonparametric tests such as Mann‐Kendall and Kendall‐tau were used to detect statistical characteristics of changes in precipitation indices and climate variables. Findings are as follows: (a) the annual total precipitation manifested a clear shifting point in 1968, with a decreasing rate of about −37.7 mm/decade, conversely, daily precipitation intensity had a clear upward trend, and extreme precipitation events above 100 mm/day became more frequent. (b) There occurred significant upward trends of 8.9 mm/decade for intense rainfall (>95th percentile) and 6.3 mm/decade for extreme intense rainfall (>99th percentile). (c) The continuous wet (dry) days showed a decreasing (increasing) trend of about −0.2 days/decade (1.0 days/decade). The decrease rate of 5‐day max precipitation is five times as large as 1‐day max precipitation. (d) For June‐September, the strengthened West Pacific Subtropical High intensity and the variation of its ridge‐axis position, the southerly shift of the upper subtropical Jetstream and the weakening of lower moisture supplement may have suppressed the northerly move of the summer rain band and delayed the development of rainy season over the study area. (e) In view of the urbanization effect, the possible causes of the precipitation externalization were investigated, and it was found that the upward trends in daily precipitation intensity and 95th percentile intense precipitation in big cities are generally higher than rural regions.