湖南汛期降水异常的时空分布特征研究

SPACE-TIME CHARACTERISTICS OF PRECIPITATION ANOMALY DURING THE RAINING SEASON IN HUNAN

利用湖南19个测站23年(1959～2001年)4-9月的降水量资料,用EOF、REOF、小波分析对湖南汛期降水的特征场分布、分区特征、周期性和突变性等时空分布特征进行了诊断研究。研究结果表明:EOF分析得到的前三个典型场可以很好的反映湖南汛期降水空间分布的异常结构,即具有整体一致的空间结构,南北相反的空间结构,中部和周围地区相反变化的空间结构。旋转后的前6个空间模态可以较好地代表湖南汛期降水的6个异常敏感区:湘北、湘中、湘南、湘东南、湘西、湘东北。利用小波分析方法研究湖南汛期降水的周期性及其突变性发现,湖南汛期降水存在着明显的3年、7年和23年的特征时间尺度和周期性振荡;并且在今后相当长的一段时间内,湖南汛期的降水将逐年减少,并将转入干旱时期。

With EOF, REOF, wavelet analysis, the space-time characteristics of precipitation anomaly during the raining season in Hunan are studied by using the precipitation data from April to September during the period 1959-2001 from 19 observational stations. The results show: (1) The most typical pattern of precipitation is the dry-wet consistence. Other typical patterns show the dry-wet difference, for example, wet (or dry) in north and dry (or wet) in south partem , wet (or dry) in center and dry (or wet) in circumference pattern. (2) The first six rotated loading vector fields represent six principal precipitation anomaly areas: North Hunan, Middle part of Hunan, South Hunan, Southeast Hunan, West Hunan, Northeast Hunan. (3) By using the wavelet analysis on the periodicity and the mutation of precipitation during the raining season in Hunan, we find that there are 3-year, 7-year and 23-year time scales and main periods of precipitation during the raining season, and the precipitation during the raining season in Hunan will decrease gradually and switch to a dry period in the near future.