近百年重庆主城区汛期降水及其集中期的变化特征

VARIATION CHARACTERISTIC OF PRECIPITATION AND CONCENTRATION PERIOD IN THE FLOOD SEASON IN CHONGQING URBAN AREA DURING THE PAST 100 YEARS

利用一种改进的定义汛期降水集中期的方法对重庆主城区近百余年汛期降水集中期进行了划分,并分析了集中期的重心日、雨量及其与汛期降水总量的关系。结果表明:近百余年重庆主城区汛期降水量线性变化趋势不明显,阶段变化显著。百余年来发生过两次突变,分别发生于1914年和1925年,分别突变为增加和减少趋势。3a左右的周期为汛期降水的主要周期。6月为降水集中期重心日发生最多的月份,8月出现相对较少,4月上半月和10月均没有出现过。近百余年重庆主城区降水集中期雨量及其占汛期降水总量的比例表现为线性增加的趋势,它们的阶段性变化比较一致,尤其是21世纪以来近10a显著偏多。集中期雨量与汛期降水之间存在很好的相关关系,但是在某些特殊年份上也存在差异。15d滑动统计方法划分的集中期雨量作为一种极端气候事件,具有较强描述灾害事件的能力,但其极端特殊性可能会表现在某些特殊年份或年际间的变化中,充分认识其规律,能为诊断和预测业务提供更为可靠的参考依据。

The precipitation concentration period(PCP) of the urban area of Chongqing are divided by an advanced method to define the PCP.The relationships between the precipitation concentration period day(PCPD),the precipitation concentration period rainfall(PCPR),and total rainfall of the flood season were analyzed.The result showed that during the past 100 years,in the urban area of Chongqing,the linear trend of the rainfall during the flood season wasn't change obviously while the phase changed a lot.The total rainfall of the flood season had two sudden changes during the past 100 years,one increasing trend in 1914 and one reducing trend in 1925.The main cycle period of the total rainfall in the flood season was around 3-year.The PCPD were most happened in June and relatively less in August,but it hadn't appeared in the first half of April and the whole October.The PCPR and its proportion of the total rainfall in the flood season showed a linear increasing trend in the recent 100 years,when the phase trend were basically the same,especially in the recent ten years,they were significantly above normal.The PCPR and total rainfall of the flood season were obviously related,but there were differences in particular years.As an extreme climate event,the PCPR with 15-day running statistical method had a stronger ability in describing extreme disaster event in the flood season,but its extreme specificity might show in the changes of some particular years and annual changes.It could provide more reliable basis for diagnosis and prediction of flood season by fully understand its laws.