近52年湘西自治州暴雨时空分布特征分析

利用1959—2010年湘西自治州8县(市)气象站观测资料,采用统计分析法对近52年该州暴雨的年代际、月际和空间分布进行分析,揭示暴雨的时空分布特征。结果表明,湘西自治州暴雨期长,暴雨的平均初日是4月11日,平均终日是9月27日;暴雨年际变化明显,20世纪60年代、70年代中后期、90年代中后期分别出现3次峰值,80年代及2000年后变化较为平缓;暴雨最多的是1996年的62站次,最少的是1961年的7站次;2—11月均有暴雨发生,4月暴雨开始明显增多,主要集中于5—8月,其中以6月最多,7月次之,其他月份依次下降;暴雨具有明显的双峰态特点,按旬统计也大致可分5月下旬—6月中旬、6月下旬—7月中旬2个峰值,2个时段分别占全年暴雨和区域暴雨总数的39.9%和44.3%。暴雨中心和大暴雨中心基本保持一致,出现频次由东部向西南部递减,永顺、古丈、泸溪县是暴雨中心,凤凰暴雨出现频次是州内最少的。影响湘西自治州暴雨的主要天气系统是切变线、低空西南急流、高空槽、冷锋和西南涡。

Analysis on the Spatial and Temporal Distribution Characteristics of Rainstorm in Xiangxi Autonomous Prefecture in Recent 52 years

Using the observation data of 8 counties (city) meteorological observatories in Xiangxi Autonomous Prefecture during 1959-2010, the interdecadal, monthly and spatial distribution of rainstorm were analyzed by statistical analysis method ,the spatial and temporal distribution characteristics of rainstorm were revealed.The results showed that the rainstorm period was long,the the average first day of rainstorm was April 11th,the last day was September 27th.The interannual variation of rainstorm was obvious, the peak value appeared in 1960s,the middle and late period of 1970s,the middle and late 1990s respectively, and the change was relatively slow in 1980s and after 2000.There were rainstorm from February to November,the rainstorm began to increase significantly in April,mainly concentrated in May to August,with the most in July, followed by the second in June, followed by a decline in other months.Rainstorm had obvious bimodal characteristic,according to statistics by ten days can also be roughly divided two peak value(from late May to middle June,from late June to middle July),the two periods accounted for 39.9% and 44.3% of the total number of annual rainstorm and regional rainstorm,respectively.The rainstorm center and heavy rainstorm center was basically consistent,the frequency of occurrence was decreasing from the east to the southwest,Yongshun, Guzhang, Luxi county was the rainstorm center,the rainstorm frequency of Fenghuang was the smallest in the state.The main weather system affecting rainstorm in Xiangxi Autonomous Prefecture was shear line, southwest low-level jet,high-level trough, cold front and southwest vortex.