Identifying regional prolonged low temperature events in China

This study examined regional prolonged low temperature (PLT) events in China from the observational station data for the period 1960–2008 using the new criteria. The new definition of a site PLT event is that the daily minimum temperature does not exceed the 10th percentile threshold of the local daily minimum temperature climatology for at least 5 days at a station. The regional PLT event is defined as at least five adjacent stations exhibiting site PLT simultaneously for >5 d. Under the new definition, 552 regional PLT events were identified, and three indices: duration, extent, and intensity, as well as a comprehensive index (CI) were used to quantify the event severity. In addition, geographical patterns and temporal variations of regional PLT events were investigated using three event categories: strong, moderate, and weak. Spatially, strong events were mainly located in the north of Xinjiang and along the Yangtze River to the south of the Yangtze River; moderate events occurred in Xinjiang and south of the Yangtze River; and weak events occurred south of the Yellow River. The variation for the annual frequency of regional PLT events in China in the last 49 years showed a significant decreasing trend with a rate of −1.99 times per decade, and the significant transition decade was the 1980s.