1951—2009年天津市主要极端气候指数变化趋势

利用1951—2009年天津市逐日气温和降水量资料,计算了极端气候指数,并研讨了其中11个主要指数的变化特征。结果表明：天津市暖日、冷夜具有基本相反的变化趋势,暖日显著增加,冷夜显著减少,且冷夜的变化幅度远大于暖日。持续暖期、霜日呈显著增加趋势,持续冷期呈显著减少趋势。降水指数中连续干日呈增加趋势,最大连续5 d降水量、日降水强度、强降水率和极强降水率及连续湿日均呈减少趋势,表明天津市干旱化倾向明显。与气温有关的极端指数大多在1993年前后出现突变,周期特征不明显。与降水有关的极端指数未现突变,但周期特征明显,大多出现10 a和4 a的周期。

Variation trends of main extreme climatic indices from 1951 to 2009 in Tianjin

Based on the daily temperature and precipitation data from 1951 to 2009 in Tianjin,a series of extreme climatic indices were calculated.Variation characters of 11 main extreme climatic indices were discussed.The results indicate that the variation trends of warm days and cold nights are contrary.Warm days increase and cold nights decrease significantly,and the variation amplitude of cold nights is larger than that of warm days from 1951 to 2009.Continuous warm stage and frost days increase,while continuous cold stage decreases significantly.Five extreme precipitation indices including continuous five days precipitation index,daily precipitation intensity index,strong precipitation rate,extreme strong precipitation rate and continuous humid days are in decreasing trends,while continuous arid days increase.It suggests that drought trend is obvious in Tianjin.The abrupt changes of extreme indices correlated with temperature occur around 1993,but their cycles are not significant.The abrupt changes of extreme indices associated with precipitation do not exist,while their cycles are significant and are usually 10 years and 4 years.