Analysis of a Rare Extreme Snowstorms in Southern Henan
[Purposes]This paper aims to study the causes of a rare extreme snowstorm in southern Henan on January 4,2018.[Methods]Using various meteorological data such as conventional observations,Doppler radar products,FY-2F longwave radiation,and NCEP,the analysis was made by weather diag-nostic methods.[Findings]The results indicate that this severe snowstorm was caused by the combined action of a strong southwest jet at 700 hPa,a southeast wind jet at 850 hPa,a shear line in the middle and lower layers,and a strong northeast wind under the reflux situation of a high-altitude trough moving eastward.[Conclusions]The low-level southwest jet and southeast wind jet transport water vapor to the southern region of Henan,with a deep wet layer and a strong water vapor convergence center above the bliz-zard area,providing favorable water vapor conditions for severe blizzards;the coupling effect of high and low altitude jet streams,the wind field configuration of"south and north",and the upward movement of warm and humid airflow climbing along cold air are all conducive to the occurrence and development of ex-treme snowstorms;the southern part of Henan Province has been located between the two shear lines in the middle and lower layers for a long time,as well as in the rising zone of water vapor convergence.The cool-ing of strong cold air causes rain to quickly turn into snow,and the snowfall lasts for a long time and is of high intensity,which is an important reason for the concentration of heavy snowfall in southern Henan;the false phase temperature,high-energy tongue extension,and dense front zone have good indicative signifi-cance for the start and fall of heavy snowfall;OLR feature analysis shows a significant negative correlation between the average low value center of OLR at 3 hours and the maximum snowfall center at 3 hours.
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