Trend In Summer Precipitation Research Articles

Trends in Total Precipitation and Frequency of Daily Precipitation Extremes over China

Abstract Based on a newly developed daily precipitation dataset of 740 stations in China and more robust trend detection techniques, trends in annual and seasonal total precipitation and in extreme daily precipitation, defined as those larger than its 95th percentile for the year, summer, and winter half years, have been assessed for the period 1951–2000. Possible links between changes in total precipitation and frequency of extremes have also been explored. The results indicate that there is little trend in total precipitation for China as a whole, but there are distinctive regional and seasonal patterns of trends. Annual total precipitation has significantly decreased over southern northeast China, north China, and over the Sichuan Basin but significantly increased in western China, the Yangtze River valley, and the southeastern coast. In western China, precipitation increase has been observed for both cold and warm seasons. However, trends differ from one season to another in eastern China. Spring precipitation has increased in southern northeast China and north China but decreased significantly in the midreach of the Yangzte River. The summer precipitation trend is very similar to that of annual totals. Autumn precipitation has generally decreased throughout eastern China. In winter, precipitation has significantly decreased over the northern part of eastern China but increased in the south. The number of rain days has significantly decreased throughout most parts of China with northwest China being an exception. Meanwhile, precipitation intensity has significantly increased. This suggests that the precipitation increase in western China is due to the increase in both precipitation frequency and intensity. In eastern China, the impact of reduced number of rain days seems to be more dominant in the north while the influence of enhanced intensity prevails in the south. Over regions with increasing precipitation trends, there have been much higher than normal frequency of precipitation extreme events. For example, significant increases in extreme precipitation have been found in western China, in the mid–lower reaches of the Yangtze River, and in parts of the southwest and south China coastal area. A significant decrease in extremes is observed in north China and the Sichuan Basin. Trends in the number of extremes and total precipitation from nonextreme events are generally in phase. An exception is southwest China where an increase of extreme events is associated with a decrease in total nonextreme precipitation.

Consistency of recent European summer precipitation trends and extremes with future regional climate projections

Summer climate over Europe in recent decades has been characterized by a drying trend and by the occurrence of especially devastating drought and flood events, such as in the summers of 2002 and 2003. We compare these trends with results from regional climate model simulations of future climate over Europe under increased greenhouse gas concentrations (GHG). We find that the projected changes in mean summer precipitation and large‐scale circulations are remarkably consistent with the observed changes in recent decades. Although we cannot directly attribute the observed changes to an anthropogenic GHG forcing, this result suggests that the observed drying trend over most of Europe might continue in the future. Our experiments additionally indicate substantial changes in the intensity and persistence of summer drought and flood. We identify the Central Mediterranean and Central/Western Europe to be especially vulnerable to increases in both summer drought and flood.