A strong precipitation event caused by the southwest vortex(SWV), which affected Sichuan Province and Chongqing municipality in Southwest China on 10–14 July 2012, is investigated. The SWV is examined using satellite observations from AIRS(Atmospheric Infrared Sounder), in situ measurements from the SWV intensive observation campaign, and MICAPS(Marine Interactive Computer-Aided Provisioning System) data. Analysis of this precipitation process revealed that:(1)heavy rain occurred during the development phase, and cloud water content increased significantly after the dissipation of the SWV;(2) the area with low outgoing longwave radiation values from AIRS correlated well with the SWV;(3) variation of the temperature of brightness blackbody(TBB) from AIRS reflected the evolution of the SWV, and the values of TBB reduced significantly during the SWV's development; and(4) strong temperature and water vapor inversions were noted during the development of the SWV. The moisture profile displayed large vertical variation during the SWV's puissant phase,with the moisture inversion occurring at low levels. The moisture content during the receding phase was significantly reduced compared with that during the developing and puissant phases. The vertical flux of vapor divergence explained the variation of the moisture profile. These results also indicate the potential for using AIRS products in studying severe weather over the Tibetan Plateau and its surroundings, where in situ measurements are sparse.
为进一步探讨高原低涡与高原大气的基本状况及其联系,通过对1981-2015年低涡频次及OLR、500 h Pa经纬向风场的统计,分析其气候变化及低频振荡特征,并初步探讨了低涡频次与其他三者低频信号之间的联系。结果表明:4-8月是低涡的频发时段;低涡频次呈逐年增加的趋势,存在显著的2 a、4 a变化周期和55 d、30 d低频振荡周期;在低涡频发期内,OLR平均值为212.2 W·m^(-2),存在显著的10~12 a变化周期和45 d、20 d低频振荡,滤波中心存在东进和西退的移动特征,在纬向上表现为向南移动,500 h Pa纬向风均值为3.56 m·s^(-1),其逐年及逐日变化均呈下降趋势,存在4 a、10 a的变化周期和75 d、45 d的低频振荡周期,30~60 d滤波信号中心以西退和北进为主要移动特征,60~90 d滤波信号中心向南移动特征明显,500 h Pa经向风以北风分量为主,其逐年及逐日变化均为减小趋势,存在4 a变化周期和10-20 d低频振荡;低涡频次与500 h Pa纬向风区域平均值在1996年发生突变;低涡频次与大气低频振荡存在密切联系,其与500 h Pa经向风呈负相关性,7-8月尤为显著,与OLR和500 h Pa纬向风在4月至7月中旬呈显著正相关,7月中旬至8月转为负相关,其中与OLR 30-60 d滤波信号呈高度负相关性;500 h Pa纬向风滤波信号中心的移动能较好的对应低涡频次空间分布的变化。
