西北区西部夏半年强降水分布与变化特征

Distribution and Change Feature of Intense Precipitation in the West Part of Northwestern China during Summer Half Years

利用国家气象信息中心西北区西部104个测站1961—2007年5-10月逐日降水量资料,分析了近47年该区夏半年强降水的时空分布特征与变化趋势。结果表明:(1)西北区西部强降水日数东多西少。最多出现在半湿润的青海高原东缘,次多出现在半干旱区的天山和祁连山区,位于干旱和极端干旱区的南、北疆盆地边缘及柴达木盆地西部,很少或从未出现过强降水日。(2)更干旱的该区西部比青海高原似更易出现强降水极大值,特别是位于峡谷、山口及冷空气通道的巴仑台、乌鲁木齐、阿合奇、若羌及阿左旗等地。(3)该区强降水日出现的最早时间呈"东、西两头早,中间晚"的格局,而最迟时间则反之。(4)该区强降水日出现频数虽呈增长态势(特别是中天山地区),但增长趋势并不显著。

Utilizing the daily precipitation data of 104 stations in the west part of Northwestern China （W-NWC） from May to October during 1961 to 2007, the temporal and spatial distribution and change tendency of intense rainfall during summer half year of nearly 47 years are analyzed. The results show that： （1） Intense rainfall frequency is more in the east of W--NWC than that in the west. The most in- tense rainfall days occurs in the east of Qinghai plateau which belongs to sub-humid areas, and the second one occurs in Tianshan Mountains and Qilian Mountains which belongs to semiarid region, and it rarely oc- curs and even has never occurred in the arid and extreme arid regions including the edge of South and North Xinjiang Basin and the west of Qaidam Basin. （2） It seems to be easier for maximum precipitation to ap- pear in the west of W--NWC where is more arid than Qinghai Plateau, especially in Balguntay, Urumqi, Akqi, Charkhlik and Alxa Left Banner. （3） The earliest date occurred intense rainfall day presents that it is earlier in the east of W--NWC and the west and later in the middle, while the latest one is opposite. （4） Intense rainfall frequency in this region （especially Tianshan Mountains） has a growing trend, but increas- ing intensity is not obvious.