常州雷暴的气候特点及多普勒雷达回波特征

利用常州基本观测站1952-2007年长序列的雷暴观测资料和多普勒雷达回波资料,采用数理统计和小波变换方法,对常州雷暴的变化规律、周期特征以及雷达回波特征进行了分析.结果表明:(1)雷暴日数年代际间差异显著.(2)雷暴年际变化很大,最大值为最小值的5.9倍;雷暴日数总体呈显著减少的趋势.(3)夏季为雷暴高发季节,占总雷暴日数的66.8%.(4)月际变化差异大,雷暴集中出现在4-9月,其中7、8月为雷暴高发月.(5)从日分布来看,傍晚出现次数最多,其次为下午,上午出现最少.(6)常州年雷暴日数分布主要表现为12a(年代际)震荡周期贯穿在整个56年里;1952-2004年存在着非常明显7a左右的次周期特征;1968-2007年还存在3～4a的小周期特征.(7)常州雷暴的雷达回波基本反射率因子一般在30～65dBz之间,回波顶高为6～17km.(9)常州雷暴雷达回波移向主要有五类:西南东北向、东南西北向、西北东南向、旋转、局地生成.另外对常州雷雨大风和冰雹进行了统计分析,发现:7月为雷雨大风最高发月;5月和7月为冰雹最高发月.

Climatic Characteristics of Thunderstorms in Changzhou Within 56 Years and Radar Echo Characters

By using the long series observational data of thunderstorms in Changzhou from 1952 to 2007 and Doppler radar data, the variation, periodic char acteristics and echo characters of thunderstorms are studied by means of mathema t ical statistics and the wavelet analysis. The results show that the interdec adal thunder storm variability is great, and the annual number of thunderstorm day has a decr easing tr end. The interannual variation in thunderstorm day number is comparatively larg e with the maxi mum being 5.9 times the minimum. The obvious seasonal variation of thunderstorms can also be detected, and the period of April to Sep tember is more frequent months for th understorms and their occurrence in July and August is the most, and over 66.8% thunder storms occur in summer season. From the diurnal distribution, the highest number i s in the evening, followed by the afternoon, at least in the morning. The result s from wav elet analysis show that the annual number of thunderstorm days in Chan gzh ou has a period of about 12 years within nearly 56 years and there is a perio d of about 7 y ears from 1952 to 2004.In addition, there is still three to four years of small cycle charact eristics from 1968 to 2007. It is found that the radar basic reflectivity of thu nderstor ms in Changzhou is from 30 to 65dBz and the echo top high is between 6 to 17km and the thunderstorm radar echoes are in five major shifts: the southwest to nor the ast, the southeast to northwest, the northwest to southeast, the rotation, and the local gen eration.The strong wind and hail storm in Changzhou are analyzed using statistic al analysis methods. It is found that the thunderstorm winds occurring in July ran k on top and the hail occurs the most in May and July.