2004-2013年“雨城”雅安的降水日变化特征分析

Analysis of the diurnal variation features of precipitation in Ya'an as the rainy city,2004- 2013

利用2004-2013年逐小时降水自动观测数据分析了"雨城"雅安降水的日变化特征.结果表明:近10 a来雅安降水主要表现出单峰型分布特征,峰值出现在北京时间24:00,谷值出现在15:00,夜间降水占年总降水量的74.5%;降水出现频次也呈现单峰型分布,峰值出现在01:00,谷值出现在14:00,夜间降水次数占全年总次数的66%;23:00-02:00是雅安最易发生降水的时段,14:00-16:00则是最不易出现降水时段.降水量和降水出现频次日变化形势均表明,雅安一年四季都具有显著的夜雨特征.近10 a来,雅安6 h以上的长持续时间降水事件主要发生在17:00-04:00,产生的过程降水量占总降水量的80.4%,对雅安降水总量的贡献占有绝对优势;持续时间≥24 h的降水事件10 a累计次数达到74次,累积降水量达到2 166.8 mm,占总降水量的14%,是长持续时间降水事件中对总降水量贡献最大的,该类事件的影响值得关注.

Hourly precipitation data observed in Ya′an,which is located in the eastern part of the Tibetan Plateau and famous as the Rainy City,from 2004 to 2013 are used to investigate the diurnal variation features of precipi-tation.It is found that the diurnal pattern of precipitation in Ya′an shows a single peak,with the peak value at 24：00 and the valley value at 15：00,and the night precipitation accounts for 74.5%of the annual total.The di-urnal curve of precipitation frequency in Ya′an also shows a single peak,with the peak at 1：00 and the valley value at 14：00,and the number of precipitation appearing at night accounts for 66.0% of the total precipitation frequency.The hourly distribution of precipitation and precipitation frequency in Ya′an both show a remarkable feature of frequent night rain.From 2004 to 20 1 3 ,the occurrence number of short-term precipitation events is primarily,accounting for 60% of the total precipitation events,but the precipitation amount of the short-term precipitation events only accounts for 19.6%of total precipitation.The long duration precipitation events mainly occur in 17：00-4：00,with the precipitation amount accounting for 80.4%of the total precipitation.There were 74 precipitation events with precipitation duration more than 24 h from 2004 to 2013,with cumulative precipitation reaching 2 166.8 mm,accounting for 14%of the total precipitation,which is worthy of attention.