利用Morlet小波变换法分析了西安市近50年月平均气温距平和月降水量距平变化的多层次时间尺度结构,发现西安市气候变化除1年的自然周期变化和20~40年尺度范围的周期变化信号在全时间域中都强外,其它时间尺度的周期变化在时间域中分布很不均匀,具有很强的局部化特征。西安市月平均气温距平变化主要表现为随机振荡,无特征尺度,而月降水量距平变化则有显著的4~5月的时间尺度。西安市气候变化受地理条件的影响较大,与ENSO的关系不象我国沿海地区那么紧密。对于大时间尺度来说,西安市气候呈暖干和冷湿结构排列,而对于小时间尺度而言则呈现为复杂的冷暖和干湿结构。

In this paper, the abnormalities of monthly mean temperature and monthly precipitation in Xi'an for the last 50 years are analyzed by the Morlet wavelet transformation. It shows that the periodic variations are localized in time domain except 1-year natural period and 20~40 years long term variations. Because of the special geographic location, the relationships between the climate variation in Xi'an and ENSO are not strong. The combination of cold or warm and wet or dry climate states are different between long and short time scales. The climate change is regularity on long time scales while the climate variation is random and complicate on short time scales. The temperature variation is mainly random while the precipitation changes with a characteristic scale of 4~5 months.