Trends in temperature and precipitation extremes over Circum-Bohai-Sea region during 1961-2008

Key words: 
• temperature /
• precipitation /
• extreme /
• trend analysis /
• Circum-Bohai-Sea region

Abstract: Using daily temperature and precipitation data of 63 meteorological stations, trends in extreme temperature and precipitation during 1961-2008 were studied over Circum-Bohai-Sea region. The results showed that at most stations, there was a significant increase in the annual frequency of warm days and warm nights and a significant decrease in the annual frequency of cold days, cold nights, frost days, and annual diurnal temperature range (DTR). Their regional averaged changes were 2.06 days/decade, 3.95 days/decade, -1.88 days/decade, -4.27 days/decade, -4.21 days/decade and 0.20℃/decade respectively. The seasonal changes had similar trend patterns to the annual results, but there was a large seasonal difference. For cold days and cold nights, winter had the most significant changes. Whether at the annual or seasonal scales, a significant warming trend was detected from trends of six extreme temperature indices, which was contributed more by changes in the indices defined by daily minimum temperature than those defined by daily maximum temperature. For precipitation indices, the regional annual extreme precipitation displayed a weak decreasing trend in terms of magnitude and frequency (RD95p, RINTEN, RPROP and CWD) but a slight increasing trend in CDD, which was all consistent with the decrease of annual total precipitation (PRCPTOT). Seasonally, the total precipitation and RD95p all exhibited an increase in spring and a decrease in other seasons with the largest decrease occurring in summer, although their trends were generally non-significant. Overall, this study showed a tendency toward warmer and drier climate conditions over Circum-Bohai-Sea region, which would have great negative effects on regional economic development and ecological protection.