The precipitation change in Eastern Forest Regions of China in recent 50 years

The Eastern Forest Region is of importance for its economic timber forest and water and soil conservation in China. It provides basic information and response to climate change by analysis on the precipitation change of the Eastern Forest Region. In this study, the missing daily precipitation data was interpolated by spatial correlation and stepwise regression methods, and the Standard Normal Homogeneity Test (SNHT) was used to examine the homogeneity of the data serial with the interpolated value(s) on all individual discontinuous points among the entire annual data serial, to obtain the interpolated value of any missed data by passing the STHT test. Finally, the full precipitation data set with a full annual series of 853 Observation Stations in the Region was completely obtained. Based upon that precipitation data set from 1961 to 2010, the long-term change trend of the annual precipitation, numbers of precipitation days, seasonal precipitation and extreme precipitation were analyzed. The results revealed that the annual precipitation increased insignificantly with a tendency of 5.58 mm/10a, but with an obvious decadal fluctuation; however, the spatial distribution of precipitation is not uniform, with decreasing trends in northern part, but increasing trends in the southern part of the Eastern Forest Region. Annual number of precipitation days had a significance reduce; showing a consistent decreasing trend in many stations in the Eastern Forest Region. The proportion of the annual amount of light rain (0.1–9.9 mm/d) and moderate rain (10.0–24.9 mm/d) to the annual precipitation and the annual number of the light rain and moderate rain days were significantly decreasing in recent 50 years. Both the percentage of annual extreme precipitation and percentage of annual extreme precipitation days had a significant tendency of increase, both intensity and frequency of extreme precipitation events have contributed to the rising of the extreme precipitation amount, extreme precipitation events which were tending to become frequencies and intensified, it might have increased the risk of severe floods in the Eastern Forest Region. In the recent 50 years, the trends of amount and days of the rainstorms (50.0–99.9 mm/d) and the heavy rainstorms (⩾100 mm/d) in the region increased significantly, with the values 5.59 mm/10a, 0.07d/10a and 4.27 mm/10a, 0.03d/10a respectively. The Mann-Kendall abrupt change test was conducted on the two different intensity rains, and the results showed the amount and days of both rainstorms and heavy rainstorms exhibited an abrupt change, the amount and days had significant increasing shift. While the remarkable increase of both the amount and days of the rainstorms presented since the middle 1980s, the heavy rainstorms since 1990s. The basic characteristics of seasonal precipitation in the Eastern Forest Region during the recent 50 years are investigated. For the seasonal precipitation in June to August and December to next February had an increasing tendency, with linear trends of 11.22 mm/10a and 5.91 mm/10a, respectively; while the decreasing tendencies in March to May and September to November in the Region, with linear trends of −2.59 mm/10a and −8.96 mm/10a, respectively.