Based on NCEP 1°×1°daily reanalysis data and conventional surface observation data,the potential vortex theory was used to analyze a strong cold air activity process of Karamay during May 15-16,2019.The...Based on NCEP 1°×1°daily reanalysis data and conventional surface observation data,the potential vortex theory was used to analyze a strong cold air activity process of Karamay during May 15-16,2019.The results showed that the weather had obviously baroclinic characteristic.A strong cold tongue extended straight to Central Asia from the high latitude area,and the cold air was strong and deep.The driving effect of cold trough could accelerate it to move southward.The Aral Sea low vortex obstructed the warm air in the north in high latitude area,and the southwest air flow in the front of the vortex conducted to the transportation of water vapor to Central Asia.Compared with the climate average field of 1981-2010,the northwest flow at 500 hPa in May of 2019 was aggressive,which had frequently influenced Xinjiang by cold air from the north high latitude regions.The east flow of the bottom layer not only input cold air to Karamay,but also formed the windward slope effect with the terrain.Moreover,it increased the vertical wind shear and induced the upward movement.The center of high potential vorticity with high latitude fell southward,and the center of low potential vorticity in Central Asia moved eastward rapidly.They combined and then moved toward Xinjiang,which made the strong cold air erupt rapidly.When the right side of the moved axis of the high potential vorticity center and the strong west flow superposed over the Karamay area,the center of the strong rainfall area appeared 6 h later.展开更多
文摘Based on NCEP 1°×1°daily reanalysis data and conventional surface observation data,the potential vortex theory was used to analyze a strong cold air activity process of Karamay during May 15-16,2019.The results showed that the weather had obviously baroclinic characteristic.A strong cold tongue extended straight to Central Asia from the high latitude area,and the cold air was strong and deep.The driving effect of cold trough could accelerate it to move southward.The Aral Sea low vortex obstructed the warm air in the north in high latitude area,and the southwest air flow in the front of the vortex conducted to the transportation of water vapor to Central Asia.Compared with the climate average field of 1981-2010,the northwest flow at 500 hPa in May of 2019 was aggressive,which had frequently influenced Xinjiang by cold air from the north high latitude regions.The east flow of the bottom layer not only input cold air to Karamay,but also formed the windward slope effect with the terrain.Moreover,it increased the vertical wind shear and induced the upward movement.The center of high potential vorticity with high latitude fell southward,and the center of low potential vorticity in Central Asia moved eastward rapidly.They combined and then moved toward Xinjiang,which made the strong cold air erupt rapidly.When the right side of the moved axis of the high potential vorticity center and the strong west flow superposed over the Karamay area,the center of the strong rainfall area appeared 6 h later.
