1961—2013年南雄降水和旱涝的变化特征分析

根据南雄市气象观测站1961—2013年降水资料,采用线性趋势分析、Z指数等方法,研究了南雄市近53年降水和旱涝的变化特征。结果表明,南雄市年平均降水量为1 524.7 mm,69%集中在汛期(4—9月),其中,前汛期(4—6月)占44%,年降水量以每年1.21 mm的速率呈弱的减少趋势,20世纪70、80、90年代降水偏多,20世纪60年代、21世纪初降水偏少。春、夏、冬3个季节的降水量变化趋势不明显,但秋季降水量却以每年1.52 mm的速率显著下降。年暴雨日平均3 d左右,6月最多,为0.6 d。53年间,旱年出现的频率22.6%,涝年出现的频率18.9%;正常年份出现频率58.5%。

Analysis of the Variation Characteristics of Precipitation and Drought/Flood of Nanxiong City in 1961-2013

Based on the precipitation observations of a meteorological station in Nanxiong City from 1961 to 2013 and with the methods of linear trend analysis and Z index, this paper studies the variation characteristics of precipitation and drought/flood of Nanxiong City in the 53 years. The result is shown as follows. The annual mean rainfall of the city is 1 524.7 mm, with 69% of it concentrated in its annual flood seasons （ April to September） and 44% of it measured in the annually first flood season （ April to June）. The annual rainfall has been decreasing by a rate of 1.21 mm/a and it rained more in the 1970s, 1980s and 1990s than in the 1960s and 2000s. The variation of rainfall is not significant in the three seasons of spring, summer and winter but it drops substantially in autumn by a rate of 1.52 mm/a. The annual number of torrential rain days is around 3 d with June being the maximum month, 0. 6 d. Drought years appear with a frequency of 22. 6% while flood years with a frequency of 18.9%, with the normal years having a frequency of 58.5%.