华南地区1961-2014年夏季长周期旱涝急转特征

根据华南地区110个气象站1961-2014年5-8月逐月降水资料,计算夏季长周期旱涝急转指数(LDFAI),经与降水量和灾情比对,LDFAI能反映出华南夏季的旱涝急转特征.采用旋转经验正交函数,趋势系数计算,线性倾向计算,T检验,M-K检测等方法,对华南地区夏季LDFAI的时空变化特征进行了研究.结果表明:① 从整体上看,华南区域平均的LDFAI趋势变化不明显,但其强度呈显著的阶段性变化特征,存在2个偏强时期和1个偏弱时期.② 从区域变化特征上可以分为5个主要空间区域,通过对各空间区域代表站的资料进行分析,1区(粤北和桂东北)和2区(粤西和桂东南)夏季LDFAI呈下降趋势,且1区下降趋势显著并在1988年发生了显著下降的突变;3区(粤东)和5区(海南岛)LDFAI呈显著上升趋势,且3区在1980年发生了显著上升的突变;4区(桂西)LDFAI呈现阶段性变化特征.③ 从年代际特征看,1区和2区LDFAI随年代下降,相应5-6月降水随年代增多.3区和4区LDFAI在1990s和2000s为较大值,该时段7-8月降水明显偏多.5区LDFAI随年代上升,相应7-8月降水随年代增多.

Features of long-cycle drought-flood abrupt alternation in South China during summer in 1961-2014

In this study, summer long-cycle drought-flood abrupt alternation index (LDFAI) is calculated based on the monthly precipitation data from May to August obtained from 110 weather stations in South China from 1961 to 2014. LDFAI, which compares the precipitation amounts under different disaster conditions, can reflect the features of drought-flood abrupt alternation in South China in summer. The spatial-temporal change of summer LDFAI in South China have been studied by rotated empirical orthogonal function analysis, trend coefficient estimation, linear trend analysis, t-test, and Mann-Kendall test. Results show the following: (1) the overall change trend of the average LDFAI in South China was not remarkable, whereas the LDFAI intensity exhibited significant periodic changes, including two strong periods and a weak period. (2) The summer LDFAI can be divided into five main spatial regions. The analysis of the data from the representative stations in different spatial regions showed that the summer LDFAI values in Region 1 (North Guangdong and Northeast Guangxi) and Region 2 (West Guangdong and Southeast Guangxi) demonstrated downward trends. The decline in Region 1 was significant, and an abrupt decline occurred in 1988. The summer LDFAI values in Region 3 (East Guangdong) and Region 5 (Hainan Island) showed significant upward trends. An abrupt rise occurred in Region 3 in 1980. The LDFAI in Region 4 (West Guangxi) exhibited periodic change features. (3) As regards the interdecadal change features of the LDFAI for the study period, the LDFAI values in Region 1 and Region 2 declined, whereas the amount of precipitation in May and June increased over the years. In the 1990s and 2000s, The LDFAI values in Region 3 and Region 4 were high, and the precipitation amount in July and August were higher than that in other months. In Region 5, the LDFAI increased, and the precipitation in July and August increased over the years as well.