1971—2011年辽宁寒潮时空分布特征

Spatial and temporal distributions of cold wave from 1971 to 2011 in Liaoning province

利用1971—2011年辽宁省58个常规观测站日最低气温资料,分析辽宁寒潮时空分布特征。结果表明:1971—2011年辽宁寒潮年平均发生频次空间分布存在两个大值中心,一个位于辽宁东北部地区,另一个位于辽西建平地区;11月大范围强寒潮出现最多。近41 a辽宁区域性寒潮呈不显著下降趋势,在20世纪70年代出现最多;区域性寒潮在10月中旬至翌年5月上旬均可出现,12月上旬至翌年2月下旬是区域性寒潮集中出现时段,出现最多的为1月;区域性寒潮出现次数存在20、13、8 a和4 a的变化周期。影响辽宁区域性寒潮的主要天气形势有小槽发展型、横槽型和低槽东移型。寒潮物理量预报指标主要有:寒潮前至少有一日升温过程;500 hPa冷中心温度≤-40℃;地面冷高压主体中心气压为1050 hPa以上,分裂小高压中心气压为1030 hPa以上;500 hPa和850 hPa急流普遍为24 m·s-1和12 m·s-1以上;850 hPa辽宁附近等温线密集程度≥5条/10纬度;风向与等温线夹角基本大于60°。

Based on diurnal minimum temperature data at 58 meteorological stations in Liaoning province from 1971 to 2011,the spatial and temporal characteristics of cold wave were analyzed.The results indicate that there are two centers of large values for annual mean frequency of cold wave.One center is located in the northeast Liaoning province,and another is in Jianping of western Liaoning province.The most widespread strong cold wave events occur in November.Regional cold wave mainly occurs in 1970s,which is in an insignificantly decreasing trend in recent 41 years.Cold wave often appears from middle ten days of October and early ten days of May of next year, and it concentrates between early ten days of December and last ten days of February of next year,especially in January.There are a 20-year,13-year,8-year and 4-year cycles for regional cold wave.Weather patterns affecting regional cold wave include a small trough type,a horizontal trough type and an east moving type of low trough. The indexes forecasting regional cold wave are as follows：there is an increasing temperature process at least one day before regional cold wave happens;temperature of 500 hPa cold centre is less than or equal to -40 ℃;the central value of high pressure system is above 1050 hPa,and pressure is more than 1030 hPa in the center of split-ting smaller high pressure;jet stream is greater than or equal to 24 m·s-1 at 500 hPa and 12 m·s-1 at 850 hPa;iso-therm density at 850 hPa around Liaoning province is above 5 strips /10 latitude,and angle between wind direction and isotherms is greater than 60°.