乌鲁木齐1991-2010年降雨特征分析

 利用1991—2010年5—9月乌鲁木齐市气象站降水量资料,分析了乌鲁木齐近20 a降雨特征。结果表明,逐小时降水量和降水频次呈现较为一致的日变化特征,均以20时以后至翌日11时左右为高值区,在下午16时达最低值;1 h降水频次最多的是量级≤1.0 mm的降水,其次是1.1 mm≤R1≤3.0 mm,但1.1 mm≤R1≤3.0 mm量级的降水贡献率最高,其次是R1≤1.0 mm。不同量级降水过程均有较为明显的年际差异,小雨过程发生的频次最多,其次为中雨、大雨和暴雨过程。前半夜为小雨、中雨和大雨过程最易发生时段,下午为暴雨过程最易发生时段。小雨、中雨、大雨和暴雨过程发生最多的时段分别为7月中旬、5月中旬、5月中下旬、5月上中旬与7月中旬及8月下旬。短时性降水(1~3 h)主要集中在前半夜,持续4~6 h和7~9 h降水多集中在前半夜到后半夜,持续10~12 h及以上的降水多发生在下午至后半夜。20 a来雨日年际变化不明显,后10 a和前10 a相比,暴雨日数有所增加,而其他量级及总雨日均减少。

Rainfall Variation during 1991-2010 in Urumqi

Based on hourly precipitation data from May to September during 1991-2010 from Urumqi meteorological station,the features of rainfall change during recent 20 years were analyzed.Results showed that the diurnal variations of hourly precipitation and rainfall frequency were consistent.The peaks of hourly rainfall and rainfall frequency both occurred from 20:00 to 11:00,and the minimum value occurred at 16:00.The frequency of rainfall less than or equal to 1.0 mm\5h-1 was the most,which was followed by the frequency of rainfall great than or equal to 1.1 mm\5h-1 but less than or equal to 3.0 mm\5h-1.Nevertheless,the contribution of the latter was the biggest to precipitation.Different magnitudes of precipitation intensity had some different yearly change.The frequency of light rain was the most,the second were moderate rain and heavy rain,and the least was torrential rain.In a day,light rain,moderate rain and heavy rain occurred with the most frequency at the first half of the night,torrential rain at afternoon.During a year,light rain occurred with the most frequency in the middle of July,moderate rain in the middle of May,heavy rain in mid-to-late May,and torrential rain in early and middle of May,middle of July,and late August.The peaks of rainfall events with duration of 1-3 hours occurred at the first half of the night,that with duration of 4-6 hours and 7-9 hours often appeared at night,and that with 10-12 hours duration often appeared in the afternoon and after midnight.The inter-annual change of total rain days is these 20 years in Urumqi was not significant.Compare to during 1991-2000,the torrential rain days increased during 2001-2010,while the days of the other magnitudes decreased.