Precipitation events should be characterized using data with high temporal resolution, such as hourly precipitation. Event-based evaluation can provide more information than the traditional equal-time-interval method by considering precipitation intermittency. This study focuses on the performance of hourly gauge observations and ERA5 products based on precipitation events in eastern China during 1979–2015. The annual frequency, duration, amount, and intensity of precipitation events are compared, and the statistics of precipitation events with different durations are also evaluated. Results show that ERA5 estimated more annual precipitation events and longer duration compared to the gauge observations, with relative deviation values of 48.75% and 49.22% at the national scale. Precipitation intensity and amount estimated by ERA5 based on precipitation events were less than those obtained from gauge observations, and the discrepancies in low-latitude regions were greater than those in high-latitude areas. The frequency of precipitation events decreased exponentially with duration for both ERA5 and gauge observations, but generally the value for the former was larger than for the latter. The statistics related to precipitation events showed smaller trends for ERA5 than for gauge observations, i.e., −0.13 h decade−1 and −0.17 mm decade−1 for the trends of duration and amount in ERA5, which contrasts with 0.03 h decade−1 and 0.14 mm decade−1 for gauge observations, respectively. These results can provide a reference for improving the parameterization scheme of the precipitation triggering mechanism in the process of model simulation.

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Precipitation plays a fundamental role in terrestrial modelling and is extremely vulnerable to climate change. It is particularly challenging to describe precipitation due to its intermittency and fluctuation at nearly all temporal and spatial scales. Precipitation variability represents the degree of unevenness in its distribution or its lack of uniformity over different scales. This study examined the seasonal variability of meteorological station precipitation observations during 1961–2018 over mainland China using entropy theory. The intensity disorder index (IDI) and apportionment disorder index (ADI) were used to characterize the distribution unevenness, including the number of precipitation days, and precipitation amounts. Six special regions were selected according to their geographical location and climate conditions to show the regional differences of the disorder indices. At the daily scale, the regional mean IDI was 0.4081 for the eastern Tibetan Plateau and the regional mean ADI was 0.9984 for north China, which were the largest value among the six regions investigated. The regional mean IDI was 0.1128 and the regional mean ADI was 0.4071 both for the Yangtze River Basin, which were the smallest value among the six regions investigated. Temporal variations of the DIs were also detected. The IDI have decreased not significantly in most regions, except increasing by 0.0223/decade and 0.0129/decade in southwest China during nighttime and daytime, respectively. The ADI decreased by −0.0191, −0.0275, −0.0229, and −0.0203/decade and passed the significant test at .05 level for northwest, northeast, north China, and eastern Tibetan Plateau at the daily scale, respectively. The results quantify the precipitation unevenness over mainland China, which can be treated as a reference for water resources management and land surface model evaluation.

Precipitation is spatially and temporally unevenly distributed. The unevenness of precipitation is crucial for climate change, as well as for water resource management, environmental risk reduction and industrial/agricultural production. In this study, gauge observations and eight reanalysis products are used to examine the unevenness of precipitation from 1979 to 2018 over China. The results show that all the reanalysis datasets can reproduce the spatial pattern of the annual number of wet days and precipitation intensity, as shown in the observations; however, most reanalyses overestimate the former and underestimate the latter. The mean cumulative fractions of the precipitation amount on the wettest 1, 5, and 10 days to annual total are approximately 9.3%, 29.8% and 45.1% in the gauge observations, and are 6.6%±0.8%, 22.1%±2.5% and 34.3%±3.5% in the reanalyses. The mean cumulative fractions of precipitation amount on the wettest 1, 5, and 10 days to annual total displays a small negative trend based on gauge observations over China (-0.06%/decade, -0.10%/decade and -0.10%/decade, respectively), but are positive and stronger in the eight current reanalyses (0.08% ± 0.08%/decade, 0.25%±0.08%/decade and 0.35%±0.10%/decade). The Japanese 55-year reanalysis is the best in quantifying the annual variability of the cumulative fractions of precipitation on the wettest 1, 5, and 10 days over China, while the ERA-Interim is the best in reflecting their trends. The reanalyses agree best with the observations in reflecting cumulative fractions of precipitation in the Yangtze River Basin and the worst in the Northwest China.