Abstract:

The two difficult prediction processes i.e.cold- and non-cold-air snowstorms in the Dalian area from 2018 to 2019 were analyzed using the data from the automatic station, conventional meteorological observation, NCEP reanalysis, Radar, and 1 km×1 km grid products.The results indicate that the process of the cold-air snowstorm has northeast airflow and strong cold advection below 500 hPa.The wind speed above 1 km is higher than that below 1 km.The process of a non-cold-air snowstorm has wind shear from near the ground to 850 hPa, a convergence line on the ground, and an inversion layer above 850 hPa.The wind direction near the ground is south and southwest.Two processes belong to unstable snowfall and both have meso and small scale convergence lines on the ground.The unstable conditions of a cold-air snowstorm are established earlier and are more unstable than that of a non-cold-air snowstorm.The cold-air snowstorm area is located downstream of the meso and small scale convergence line uplift area, while the non-cold-air snowstorm area is located in the meso and small scale convergence line uplift area.When the dry and cold air from the northwest passes through the Bohai sea surface, the air-sea interaction makes the water vapor on the warm ocean surface evaporate and converge for a long time, which is the source of the water vapor of the cold-air snowstorm.The water vapor of the non-cold-air snowstorm mainly comes from the horizontal transportation of warm and humid air in the south, and the water vapor condition is established for a short time.The cold-air snowstorm affecting Dalian has the radar echo moving from northwest to southeast and a large area of strong echo.Inversely, the non-cold-air snowstorm has the radar echo moving from southwest to northeast and moves consistent with the moving direction of the echo.

Key words: The cold-air snowstorm, The non-cold-air snowstorm, Meso-scale, Grid products