摘要
利用观测资料对2013年7月7-11日（简称＂7·7＂）发生于四川盆地西部的极端暴雨及局地对流条件进行分析,结果表明：（1）这次持续性暴雨由对流性降水和稳定性降水组成,前期对流明显,小时雨量大,中尺度对流系统云顶亮温低,有冷云区,PPI速度图上有逆风区,45 dBZ以上的强回波厚;中后期稳定性降水明显,小时雨量小,但持续时间长,云顶亮温较高,无冷云区,且回波强度在20-40 dBZ左右,PPI速度图上存在＂牛眼＂结构,暴雨区低层东北风强。（2）对流性与稳定性降水的转换条件与CAPE变化和垂直风切变有关,降水增强（减弱）期,有（无）CAPE值,低层风速小（大）但中高层风速大（大）,垂直风切变较强（弱）。（3）在低空南风较弱和东北风偏强的背景下,地面气旋性流场引起的辐合不仅为暴雨提供水汽,而且中尺度辐合线亦为降水发生提供了抬升机制,尤其是在热力条件和低空水汽输送不利的层结稳定阶段,地面气旋流场显得更加重要。
Using a variety of observational data to analyze the extreme precipitation characteristics of the western Sichuan Basin occurred on July 7th to July 11 th,2013 and local convective conditions of the heavy rain,the results showed that：（1）the continuous heavy rain includes two stages of convection and stratification stability,at early stage,convective precipitation is obvious and hour precipitation is strong,the cloud top temperature of mesoscale convective system（ MCS） is low and exists cold cloud area,PPI velocity of Chengdu radar displays that there is inverse velocity region,echo thickness of values of≥45dBz was large. In the late period,stratification stability precipitation is obvious and hour precipitation is small,but the long duration,the cloud top temperature is higher,no cold cloud area and echo intensity is around 20- 40 dBz,also the existence of＂bull＇s eye＂structure of Chengdu radar PPI velocity map shows that the low northeast wind is remarkable in heavy rain area.（2） the physical factors about convective precipitation converting to stratification stability precipitation mainly had relations with CAPE variation and vertical wind shear,at precipitation strengthened（weakened） period,there is（no） CAPE value and low wind speed is small（large）,but upper-wind speed is high（high）,the vertical wind shear is significant（not significant）.（3） Under the background of weaker the low-level south wind and strong northeast wind,the convergence caused by ground cyclonic flow field not only provide water supply for the heavy rain storm,but also provides the uplift mechanism of mesoscale convergence line the trigger for precipitation,especially at poor low-moisture transport and stable stratification stage,flow cyclone near the ground becomes more and more important,so the ground cyclone flow field plays an important role in the heavy storm.
出处
《高原山地气象研究》
2014年第3期10-16,共7页
Plateau and Mountain Meteorology Research
基金
2014年预报员专项(CMAYBY-60)
四川省气象局青年基金(川气课题2012-青年-01)
四川省气象局高原气象观测与应用创新团队
关键词
四川盆地
极端暴雨
地面气旋性流场
垂直风切变
Sichuan Basin
the extreme heavy rain
the ground cyclone flow field
vertical wind shear
