Abstract:

Using the conventional meteorological observational data and 1°×1° reanalysis data from the NCEP (National Centers for Environmental Prediction), the weather situation and physical quantity diagnosis and analysis of the extreme blizzard process in Liaoning province from 6 to 9, November, 2021 were carried out.The results show that the extreme blizzard process is mainly affected by the Northeast cold vortex and strong cyclone, the maximum snowfall is 80.8 mm, and the maximum snow depth measured at 20 stations exceeds 30 cm.The main cause of extreme blizzard is the long duration of strong water vapor transport and water vapor convergence, with the maximum values of 18 g·hPa^-1·s^-1·cm^-1 and -7×10^-5 g·hPa^-1·cm^-2·s^-1, respectively.The strong ascending motion produced by abnormally strong convergence at the low level and divergence at the high level, with a central value of -3.0 Pa·s^-1, is indicative of an extreme blizzard forecast.The baroclinic forcing and strong horizontal frontogenesis at 850 hPa are important mechanisms for the occurrence and development of this extreme snowfall event.The configuration of the moist potential vortex, with MPV1>0 and MPV2 < 0 indicates that the increase of cyclonic vorticity and symmetric instability provides favorable conditions for the occurrence of the blizzard process.

Key words: Northeast cold vortex, Water vapor convergence, Upward motion, Baroclinicity, Moist potential vortex