Variation Diagnosis and Regional Comparison of Different Intensity of Rainfalls and Their Contribution to Total Rainfall in China in the Context of Global Warming

Using the data of 545 meteorological stations in 1961-2015, according to the rainfall intensity classification standard issued by the China Meteorological Administration, the rainfall events were divided into six types: light rain, moderate rain, heavy rain, torrential rain, downpour and heavy downpour. The latter three were recorded as total torrential rain, and all the six were recorded as the total rainfall. In terms of the interannual rainfall and rainy days, the whole China was regarded as an object. Firstly, the annual rainfall and rainy day of different intensity of rainfalls of 545 stations in 1961-2015 were calculated. Then, the variation trend of rainfall and rainy days was calculated. Finally, the variation trend of contribution of different intensity of rainfalls and rainy days to total rainfall and rainy days were diagnosed. It obtained the following results. (i) The light rain in China was declining from 1961 to 2015, and the trend values of light rain and rainy days were -411.44 mm/yr and -136.99 d/yr, respectively. Heavy rain and total heavy rainfall showed an increasing trend, with rainfall and rainy day trends of 127.02 and 463.94 mm/yr and 7.93 and 4.24 d/yr, respectively. The total rainfall showed a “hockey” phenomenon of “first rise, then decline”, and the trend values of rainfall and rainy days were 204.29 mm/yr and -95.81 d/yr, respectively. Except the northern region, the rainfall in most parts of China was dominated by increasing trends and was moving towards extremes. (ii) In terms of rainfall contribution rate, the contribution of light rain to total rainfall showed a declining trend, and the trend values of rainfall and rainy day contribution were both -0.11%/yr. The contribution of other intensity rainfalls to total rainfall showed an increasing trend. The contribution of torrential rain to the total torrential rain showed a declining trend. The contribution trends of rainfall and rainy days were -0.06% and -0.03%/yr, respectively. The contribution of downpour and heavy downpour to total torrential rain showed an increasing trend, indicating the intensity of torrential rain in China is increasing. Although the contribution rate of different intensity of rainfalls to total rainfall was different in different areas of China, the contribution rate of heavy rainfall to total rainfall in most areas showed an increasing trend. (iii) Through comparing the rainfall and rainy days of six different intensity of rainfalls, it can be found that China's heavy rainfall events are increasing and the rainfall intensity is developing towards extremes.