Changes in Unevenness of Wet‐Day Precipitation Over China During 1961–2020
Jingya Han, Chiyuan Miao, Qingyun Duan, Jingwen Wu, Jiaojiao Gou, Haiyan Zheng
Abstract
Abstract Precipitation falls unevenly in space and time, which has significant consequences for human society and natural ecosystems. Based on 2,134 gauged observations during 1961–2020 and historical simulations of 14 models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6), we analyze precipitation unevenness over China in terms of the spatiotemporal distribution of wet days (>1 mm) and wet‐day precipitation amount throughout the year. We also explore precipitation extremes related to the unevenness. Spatially, precipitation shows medium unevenness in China. Temporally, the unevenness in distribution of wet days increases from southeast (generally humid) to northwest (generally arid). This temporal unevenness weakened in large parts of western China during 1991–2020 relative to 1961–1990. As for precipitation amount, the distribution of precipitation that falls on wet days is more uneven in water‐limited regions compared with humid regions. Associated with this unevenness, between 1961 and 2020, the top 50% of annual precipitation fell in approximately the 12 wettest days, and the maximum 1‐day precipitation for the year contributed 10% on average to annual precipitation. The period 1991–2020 shows overall greater unevenness in eastern China and less unevenness in western China relative to the first 30 years. Multimodel ensemble means of CMIP6 simulations agree with the basic spatial pattern of observations, while underestimating the magnitude of temporal unevenness of precipitation. If these regional differences in precipitation unevenness were to persist over time, this would likely create some new challenges for water resource management in these areas, e.g., flash drought.