Analysis of a High-Impact Cold Surge for Aviation over the Low Latitude Plateau

On February 19-22， 2022， Yunnan province， located on the low latitude plateau， experienced a large-scale cooling， rainfall and snow weather process， leading to the cancellation， delay， and return of multiple flights at eight airports.Focusing on this high-impact weather， this paper employs rain gauge data， ERA5 reanalysis data， and wind profile radar data to investigate the circulation causes， features of the cold front activity， and their impacts on aviation.The results show that： （1） This low-temperature rain and snow weather was a large-scale cold surge process that happened under the joint influence of a cold front and the southern branch trough.Before February 21， mainly affected by the cold front， the temperature dropped sharply with mild precipitation.The primary impact on aviation was aircraft turbulence caused by strong wind shear and unstable stratification.Subsequently， with the westward of the southern branch trough， precipitation increased， and the adverse weathers， such as airport snow cover， low-level clouds， thunderstorms， and wind shear， imposed a significant impact on flights.（2） The main body of the cold front regime was located below 700 hPa.When the cold surge out broke， the cold air leading by low-level easterly winds rushed westward with a nose-shaped forehead.The strength and thickness of the low-level easterly winds correspond well with those of the cold air mass； the warm westerly wind in front of the front climbs along the front， forming a inversion layer over the cold air mass.（3） When the front strongly developed and moved westward， the high value belts of the frontogenesis function at 800 hPa could well indicate the position and intensity of the front lines.The convergence of easterly behind the front and warm westerly before the front caused a significant updraft over the frontogenesis area.Meanwhile， the Richardson numbers （Ri） were small in the areas where the vertical temperature gradient was large below 650 hPa before the front and in the near-surface layer behind the front， suggesting the potential turbulence regions.（4） Wind profile radar data indicated that during the maintenance period of low-level easterly winds， the strengthening of westerly winds above 2 km had a certain indicative significance for precipitation.When the low-level easterly winds weakened and disappeared， the process ended.