A snowstorm event caused by an explosive cyclone happened in the eastern region of Heilongjiang prov-ince on November 25,2013.Based on various conventional observation data and the NCEP reanalysis data,devel-opment of cyclone and characteristics of snowstorm were diagnosed and analyzed.The results show that the cy-clone located in right rear side of north branch jet exit region and left front side of south branch jet entrance region is always in front of the development trough with evacuation structure and under the strong upper level divergence, and these are favorable to development of explosive cyclone.The different scales secondary circulations result from coupling of upper and lower jets.The coupling of high-low jet induces high divergence area overlaying on the top of low convergence area,consequently leading to intense ascending movement,strengthening cyclone strength and intensity of snowfall.Track of explosive cyclone is mainly located in the sea,so water vapor of the cyclone is a-bundant.Low level jet flows in eastern side of the cyclone,which strengthens water vapor transported northward and enhances snowfall in the eastern region of Heilongjiang province.Appearance of water vapor convergence cen-ter under 850 hPa suggests that snowfall intensity will increase,and it is corresponding with strong snowfall.Snow-fall intensity decreases when thickness of vapor saturation region decreases to lower layer of troposphere.Snowfall has a good relationship with frontogenesis of frontal area in upper level,while the influence time and location of strong frontal zone in lower level which moves through the eastern region of Heilongjiang province from south to north have corresponding relationships with snowstorm.Frontal area leans northward with the heights.Warm frontal zone in upper level moves away,and snowstorm intensity reduces;frontal zone moves out,and snowfall is over.
Explosive cycloneHeavy snowstormCirculation characteristicsJet streamFrontal zone
国家科技期刊平台
NSTL
维普
万方数据
