黄土高原一次疑似龙卷天气的中尺度特征OACSTPCD

The mesoscale characteristics of a severe convective weather event that occurred in Yulin on August 4th,2013 were analyzed using conventional observation data,including radiosonde and ground observations,as well as minute-resolution data from automatic meteorological stations and Doppler radar.The results show that this event was likely a tornado event triggered by a supercell.Considering the larger-scale circulation patterns,a northwesterly airflow in the middle troposphere led to strong dry-cold advection.Additionally,a southwesterly jet and a shear line in the lower layers contributed to a structure with dry-cold conditions at the top and wet-warm conditions at the bottom.In terms of the environmental conditions,prior to and during the formation of the supercell,the convective available potential energy(CAPE),lifting condensation level(LCL),and vertical wind shear met the necessary thermal instability and dynamic criteria for the development of a tornado event.The radar echoes exhibited a distinct hook-shaped pattern along with a strong mesocyclone.Moreover,the presence of positive and negative velocity pairs with echoes exceeding 60 dBZ indicated the echo pattern typically associated with a tornado.Before and after the formation of the supercell,several tornado vortex signatures(TVS)were detected as they moved through the Yulin area in a north-to-south direction.At the surface,meteorological conditions underwent significant changes,including a decrease in atmospheric pressure at the ground level and the rapid strengthening and rotation of winds at the 10-meter level.These changes corresponded to the observed characteristics of an ongoing tornado event,suggesting a high probability of a tornado occurrence.