Analysis of Causes and Mesoscale Cloud Clusters of a Backflow Blizzard Process in Central Inner Mongolia.

Based on the conventional observation data, daily reanalysis data from NCAR/NCEP, and TBB data derived from FY-2G infrared cloud images in April 2018, a heavy snowfall weather process in central Inner Mongolia from April 4 to 6 in 2018 was analyzed. The results show that the low trough at 500 hPa, the southerly wind jet stream at 700 hPa, and the inverted trough on the ground were the main influencing systems causing this blizzard. The transportation of warm and humid air by the southerly wind jet stream at 700 hPa and intense water vapor convergence provided sufficient water vapor conditions for the blizzard, and the moist layer in the blizzard area was deep. The low-level MPV in the blizzard area was <0, and the atmosphere was in a conditional symmetric instability state. The coupling of the upper and lower-level jets induced strong ascending motion. With the invasion of cold air, a low-level cold pad was formed, so that the warm and humid air tilted upward. The secondary circulation updraft triggered by the wet Q vector system released the conditional symmetric instability energy, so that the sloping motion was more intense, and the heavy snowfall appeared. Meanwhile, there was a good correspondence relationship between the blizzard area and the large-value area of low-level wet Q vector divergence. The mesoscale cloud clusters continuously generating, merging, and moving eastward in Hetao area were the direct cause of this blizzard, and the TBB of the cloud clusters was ≤ -56 ℃. The blizzard happened in the the edge gradient and large-value area of TBB. [ABSTRACT FROM AUTHOR]