Atmospheric precipitation is a critical component of the terrestrial water cycle. For detecting and understanding the response of the water cycle to global warming at the regional scale, it is important to analyze the temporal and spatial variations in daily precipitation at the continental or subcontinental scale. In this study, daily precipitation data from the US National Climate Data Center (NCDC) and the China National Reference Climate and Basic Meteorological Stations for the period of 1951-2009 were used to analyze the long-term variations in precipitation over East Asia (25°N-55°N, 105°E-145°E). After basic quality control, 619 stations were chosen. Based on the percentile thresholds, the daily rainfall was classified into light, moderate, intense, and very intense. The regional average time series were obtained by the method of the area-weighted average for the grids. The spatial and temporal patterns of the long-term changes in all kinds of precipitation events were also analyzed.
The results showed that the average regional precipitation and precipitation intensity decreased during the last 59 years (1951-2009), whereas the rainy days exhibited no prominent trend. In most of northern China, eastern Mongolia, southern Russian-Far East, and most of Japan, the amount, frequency, and intensity of annual precipitation generally decreased. However, the southern part of Middle Siberia, the Korean Peninsula, and the Yangtze River basin witnessed increasing trends of the precipitation index series. The amount, frequency, and intensity of seasonal precipitation increased in winter and spring, and decreased in the summer and autumn except for the summer precipitation intensity. The annual seasonal precipitation variability in the last decade was gentler than the previous.
The regional average precipitation decreased in all categories in 1951-2009. The moderate precipitation decreased faster than the precipitation frequency, whereas the intense and very intense precipitation decreased slightly slower than the precipitation frequency. The moderate, intense, and very intense precipitation frequencies decreased during the last 59 years, and only the light precipitation frequency increased. Note that for the last 30 years (1980-2009), the overall precipitation intensity decreased, whereas the overall precipitation frequency increased for most areas in the study region. Most of the stations south of the 45°N latitude recorded increased annual precipitation; however, the daily precipitation intensity was less extreme.