Trends in temperature and precipitation extremes over Circum-Bohai-Sea region, China

Trends in temperature and precipitation extremes from 1961 to 2008 have been investigated over Circum-Bohai-Sea region, China using daily temperature and precipitation data of 63 meteorological stations. The results show that at most stations, there is a significant increase in the annual frequency of warm days and warm nights, as well as a significant decrease in the annual frequency of cold days, cold nights, frost days, and annual diurnal temperature range (DTR). Their regional averaged changes are 2.06 d/10yr, 3.95 d/10yr, −1.88 d/10yr, −4.27 d/10yr, −4.21 d/10yr and −0.20°C/10yr, respectively. Seasonal changes display similar patterns to the annual results, but there is a large seasonal difference. A significant warming trend is detected at both annual and seasonal scales, which is more contributed by changes of indices defined by daily minimum temperature than those defined by daily maximum temperature. For precipitation indices, the regional annual extreme precipitation displays a weak decrease in terms of magnitude and frequency, i.e. extreme precipitation days (RD95p), intensity (RINTEN), proportion (RPROP) and maximum consecutive wet days (CWD), but a slight increase in the maximum consecutive dry days (CDD), which are consistent with changes of annual total precipitation (PRCPTOT). Seasonally, PRCPTOT and RD95p both exhibit an increase in spring and a decrease in other seasons with the largest decrease in summer, but generally not significant. In summary, this study shows a pronounced warming tendency at the less rainy period over Circum-Bohai-Sea region, which may affect regional economic development and ecological protection to some extent.