Analysis of the periods of maximum consecutive wet days in China

Using daily precipitation data from China during the period 1960-2005, the maximum number of consecutive rainy (or wet) days is investigated. Linear regression and the modified Mann-Kendall test are used to evaluate trends in the wet days. Results indicate (1) that four consecutive wet days occur more frequently; however, their (fractional) contribution to the total amount of precipitation is small. On the other hand, one wet day is prevalent in winter and its (factional) contribution is the largest. (2) In the northwest China, the number and the total precipitation of the maximum consecutive wet days are increasing annually as well as in winter, implying wetting tendency in northwest China and in winter. (3) Decreasing total precipitation is observed in the basins of the Yellow, Liaohe, and Haihe rivers. The number and the fractional precipitation contribution of the maximum consecutive wet days are also decreasing, pointing to a higher risk of droughts in these regions, and these regions are heavily populated with highly developed socioeconomy and are also the major agricultural areas. In this sense, negative impacts are evident because of increasing drought risk as a result of decreasing total precipitation. Besides, a higher risk of droughts can also be expected in southeast China in winter, but a lengthening of maximum consecutive wet days is not evident in China. Higher drought risk in southeast China may threat the water supply, for example, the water supply for Hong Kong and Macau. However, increasing fractional contribution of shorter consecutive wet days may imply intensifying precipitation in China.