关键词: 水汽输送, 干侵入, 动力垂直结构, 锋生过程, 雷达回波

Abstract: An extreme blizzard and gale weather process over Jilin province on February 21 to 22 in 2015 was diagnosed and analyzed using the conventional meteorological observation data,regional automatic station precipitation data and the NCEP (National Centers for Environmental Prediction) 1°×1° 6-hourly reanalysis data.The results show that a high-level cold eddy combining with eastern expansion of the ground Mongolia cyclone is a main factor influencing this blizzard weather event.Overlaying of temperature and pressure fields at 850 hPa in reverse phase is consistent with the typical gale weather situation over Jilin province.Corresponding snowfall process can be divided into two phases,namely,snowfall at warm and then cold areas.The first phase of snowfall is triggered by the low-level southerly jet with an abnormally abundant water vapor coming from Bohai and Yellow Sea.The dynamic conditions in this phase are relatively weak.In the second phase,the water vapor condition is weaker than in the first phase.It is mainly due to the westerly transport of water vapor converging at the Sea of Japan,which is controlled by the easterly and northerly jets in the north part of the low vortex.While its dynamic conditions are stronger than those of the first phase.During the heavy snowfall period,the dry intrusion and frontogenesis process are obvious,and the role of cold air is significant.When the heavy snowfall occurs,the echo intensity is general within 15-25 dBz,and the echo height is equal or less than 4 km.Meanwhile,the snowfall intensity in the cold area is closely related to the strengthening of shear line and the invasion of cold air.

Key words: Water vapor transportation, Dry intrusion, Vertical dynamic structure, Frontogenesis process, Radar echo