ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Analyses on the SpaceTime Distribution Characteristics and Their Influence Systems of Heavy Snow in Jiangxi
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Abstract:
Based on NCEP 2.5°×2.5°reanalyzed data and daily observation data, the characteristics of climatic situation and influencing systems of 50 regional heavy snow events in Jiangxi from 1980 to 2008 were summarized and analyzed. The results show that: The heavy snow events in Jiangxi had a period of about 5 years. Before the 1990s, heavy snow events happened often and had large variations. Afterwards, the interannual variations tended to occur less frequently. As to the spatial variation, the frequency of heavy snow was characterized by the distribution of gradually reducing from the northwest to the southeast. During heavy snow periods, the blocking high and the frontal zone in midlow latitudes were extremely powerful. The 80% heavy snow events were associated with blocking high, most of which were Baikal Lake blocking highs. While 70% of the events were associated with the south branch trough. Most heavy snow events were associated with shear lines at 700 hPa. And there was significant southwest jet with an over 16 m·s-1axis at the south of it. Normally, the snowing region was 1-3 degrees in latitudes south of a cold shear line or at the neighborhood of a warm shear line. If there was a shear line at 850 hPa simultaneously, the snow would be heavier. The 98% of the events were accompanied by inversion layers in the troposphere. The vertical distribution of temperature was characterized by <1 ℃ at 1000 hPa, ≤-2 ℃ at 925-850 hPa and ≤0 ℃ at 700 hPa. Mostly, the surface cold air was from the middle area where an extremely strong Mongolia cold high offered a favorable condition for snowfall.
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