近40年南阳市降水量及降水类型分布特征

Distribution characteristics of precipitation amount and type of Nanyang city in recent 40 years

统计1970—2009年南阳市气象站降水数据,分析了近40年南阳市降水量随时间的变化特征及降水类型的分布特征,研究结果表明:(1)近40年南阳市的月均降水量呈单峰变化趋势,7月份月均降水量最大,占年均降水量的25%.(2)近40年来,南阳市年降水量呈波动增加趋势,其年均值为765.2 mm,以24.9 mm/10a的速度增加.(3)近40年南阳市雨季年降水量呈波动增加趋势,其年均降水量为556.1 mm,占年均总降水量的72.9%;雨季和旱季年降水距平百分率波动不大,降水量年际间较稳定.(4)2000—2009年南阳市大雨、暴雨和大暴雨事件发生的次数分别占近40年来其总发生次数的22.2%、34.9%和33.3%,自2000年以后,南阳市大雨次数逐渐减少,而暴雨、大暴雨次数逐渐增加,增加了年降水量的不确定性.

Variation characteristics of precipitation amount and types were analyzed based on measured precipitation data during 1970—2009,which came from Nanyang meteorological stations belonging to the National Meteorological Center that is subordinate to the China Meteorological Administration. The results showed that：（ 1）The variation trend of mean monthly precipitation expressed unimodal curve,and the amount in July was the maximum accounted for 25% of the annual average amount in the study period.（ 2） The annual mean precipitation was 765. 2 mm during the study period,which increased by 24. 9 mm /10 a with the increment of annual series.（ 3） Annual precipitation in rainy season increased with the increment of annual series,which had a mean valve of 556. 1 mm accounted for 72. 9% of total annual precipitation. The difference was not significant between rainy season and dry season by consideration of precipitation anomaly percentage.（ 4） The proportions of heavy rain events,rainstorm events and downpour events account for total precipitation events were 22. 2%,34. 9%and 33. 3% respectively during 2000—2009. The numbers of heavy rain decreased but the numbers of rainstorm and downpour increased since 2000.