中亚低涡背景下新疆阿克苏地区一次强对流天气形成的干侵入机制

摘要

利用风云卫星资料、地面自动站资料、NECP/NCAR (0.25°×0.25°)再分析资料,对2017午6月7日一次中亚低涡背景下新疆阿克苏地区强对流过程的于侵入特征进行分析.结果表明:(1)此次强对流天气发生在稳定的“两脊一槽”环流形势下,产生于中亚低涡底部西北气流中.强对流过程伴随着α-中尺度对流云团的发展和低层α-中尺度涡旋的活动,强对流天气发生在α-中尺度对流云团TBB梯度最大处和低层生命史较短的α-中尺度涡旋配合切变线活动期间.(2)干侵入增强了大气的位势不稳定,为对流发展储备充沛对流有效位能,为α-中尺度对流云团和α-中尺度涡旋的发生、发展提供有利的环境条件.(3)应用湿位涡对于侵入过程诊断分析发现,低层湿位涡的垂直分量(MPV1)负值带(湿位涡的水平分量(MPV2)正值带)的分布和移动代表了低层对流(斜压)不稳定区和辐合区的分布和移动,强对流发生在MPVI负值中心(MPV2正值中心)附近.中低层负的MPVI、正的MPV2有利于低层气旋式涡旋发展,涡旋演变为切变线,将水汽和熊量向上输送,产生强对流天气.%Based on TBB of FY-2G satellite,automatic weather stations' observations and NCEP/NCAR reanalysis data with 0.25 ° ×0.25° spatial resolution,the dry intrusion during a severe convective weather process under the background of Central Asian vortex in Xinjiang Aksu area was studied.The results are as follows:(1) The severe convective weather occurred under the circulation situation of stable "two ridge one trough",and it produced in the northwest air flow which was located in the bottom of Central Asia vortex.Strong convective weather coupled with development of meso-α scale convective cloud clusters and the meso-α scale vortex in low level,and it occurred in the area of maximum gradient of TBB and during the period of short life history meso-α scale vortex and the shear line activity.(2) Dry intrusion enhanced the potential instability of the atmosphere and reserved abundant CAPE for development of the convection and provided favorable environmental conditions for development of the meso-α scale convective cloud clusters and meso-α scale vortex.(3) By diagnostic analysis of moist potential vorticity for dry intrusion,the distribution and movement of the negative values band of the vertical component of moist potential vorticity (MPV1) (the positive values band of the horizontal component of moist potential vorticity (MPV2)) represented the distribution and movement of the convective (oblique pressure) instability region and convergence zone in low level.The strong convection occurred near the negative center of MPV1 (the positive center of MPV2),and negative MPV1 and positive MPV2 were conducive to the development of cyclonic vortex in low level,and cyclonic vortex evolved into a shear line,which transported water vapor and energy upward for strong convective weather.