摘要
利用ncep 1°×1°再分析资料和地面加密自动站资料,采用动力诊断分析方法,对2008年9月22～26日发生在四川盆地西北部连续性暴雨的形成机制进行探讨。分析表明:连续性暴雨天气过程前期(对流性降水阶段),湿位涡正负区叠置的形式有利于低层气旋式辐合发展,强降水出现在对流层中下部MPV1<0和低层MPV2>0的范围内,而MPV1负值中心和MPV2正值中心及其包围的密集区,是暴雨产生的警戒区。后期(稳定性降水阶段),对流层高层MPV2负值位涡舌的向下伸展,有利于中低层大气斜压性增强,使垂直涡度发展,降水维持。湿螺旋度垂直分布能很好地反映暴雨发生时大气的动力特征,暴雨区上空低层正涡度、水汽辐合旋转上升与高层负涡度、辐散相配合,是触发暴雨的有利动力机制。强降水发生时段,湿螺旋度有显著增加,这对于降水发生的预报要优于z螺旋度。
Using NCEP global 1 °×1 ° final-analysis data and the ground encryption unattended station material,the forms mechanism of the continuity storm in the northwest side of subtropical high is discussed with dynamic method.The results show that： It is advantage to the development of the rain storm that plus positive zone just over minus one in early period The negative value center of MPV1 and plus center of MPV2 and the surrounding compact district,is an alert area which the rainstorm produces.In later period,the negative value of MPV2 in upper air of the troposphere extended downward to the surface layer,it is advantage to enhance the barocliny of atmosphere and the vertical vorticity development,the precipitation maintained.The moisture helicity can reflect the dynamic character of weather when the rainstorm occurred,and divergence of negative vorticity on higher level matched convergence of positive vorticity and vapor rotate rising on lower leve1 is a dynamic mechanism to trigger heavy rain.Moisture helicity was superior to z-helicity for the precipitation forecast because it＇s increasing obviously at the time of strong precipitation.
出处
《高原山地气象研究》
2012年第1期61-66,共6页
Plateau and Mountain Meteorology Research
基金
中国气象局预报员专项(CMAYBY2011-044)
四川省气象局2011年青年基金项目(2011-01)
关键词
副高
台风
机制
湿位涡
湿螺旋度
subtropical High
typhoon
mechanism
moist potential vorticity
moisture helicity
