西安夏季和冬季城市热岛的多时间尺度变化特征

Multi-Time-Scale Characteristics of Urban Heat Island in Xi'an's Summer and Winter

基于自动气象站2008年逐时气温观测资料，建立了西安市夏季和冬季城市热岛强度时间序列，采用复Morlet小波变换的方法研究了城市热岛的时间尺度（变化周期）结构及其变化特征，并利用小波方差诊断了各热岛周期振荡的强度。结果表明，冬季城市热岛的尺度结构比较简单，存在24h和144～192h2个主热岛周期，夏季城市热岛的尺度结构较复杂，其主热岛周期为24h和96～120h。日变化和周变化是西安城市热岛的主要变化周期，强热岛主要出现在工作日，弱热岛主要出现在周末。此外，还讨论了引起城市热岛日变化和周变化的驱动因子及其形成机制。

Based on the hourly data of air temperature observed from automatic weather stations in Xi＇an,the time series of urban heat island （UHI） intensity in the summer and winter of year 2008 were set up. Complex Morlet wavelet transform was employed to analyze the time scale （variation period） structure and characteristics of UHI. And wavelet variance was used to diagnose the oscillation intensity of UHI periods. It was found that the time scale structure of UHI was simple in winter while complex in summer. The primary UHI periods were composed of 24 h and 144-192 h in winter and 24 h and 96-120 h in summer. Diurnal and weekly variations of UHI were the dominant UHI periods in Xi＇ an. For weekly periods,intensive UHI occurred on weekdays, while weak UHI on weekend. Moreover, the causes of the diurnal and weekly periods of UHI were also employed.