Long-term changes in total and extreme precipitation over China and the United States and their links to oceanic-atmospheric features

摘要

We investigate the variations of total and extreme precipitations over China and the United States, focusing on long-term changes. We also explain the features of precipitation by changes in sea surface temperature (SST) and atmospheric circulation. Features of total precipitation and the ratio of extreme to total precipitation are different between China and the United States, and differences occur in both annual and seasonal means. Both total precipitation and precipitation ratio show large seasonal and regional variations over China, but change modestly over the United States Annually, China total precipitation changes insignificantly and the ratio shows only a slight positive trend. However, the US annual total precipitation increases significantly, although the ratio decreases moderately. In China, the ratio exhibits positive trends in all seasons and total precipitation shows small positive trends except a negative trend in fall. The US total precipitation increases remarkably in all seasons except winter when a slight decrease occurs, and the ratio decreases in winter and summer but increases in spring and fall. The change in China precipitation ratio has a strong link to SSTs around the Indian Ocean and the South and East China Seas, and the change in US total precipitation is associated with changes in the Indian Ocean and eastern Pacific SSTs. These relationships become weaker when the trend of total precipitation or precipitation ratio is removed, indicating an impact of SST on the long-term change in precipitation. The trends of US total precipitation and China precipitation ratio are also linked to the long-term changes in atmospheric circulation including the trade wind, the North Pacific anticyclone, and the circulation patterns over Asia. In most cases, the total and extreme precipitations are associated with similar SST and atmospheric patterns, except in China where the annual extreme precipitation is associated with SST and circulation features as is the precipitation ratio.