中国上空平流层准零风层的特征分析

Analysis of the Characteristics of the Stratospheric Quasi-zero Wind Layer Over China

利用ECMWF提供的ERA-40再分析风场资料首次分析了中国上空平流层准零风层的特点及其随季节和地理位置的变化特征.结果表明,准零风层一般处于18～25 km高度范围内,零风线所在的高度随时间和地理位置的不同稍有变化.根据准零风层随纬度的变化特征,中国上空可以分成三个区域:低纬地区(5°N～20°N)、中低纬过渡区域(20°N～32.5°N)和中高纬地区(32.5°N～55°N).低纬地区一般在冬季和初春有准零风层结构存在;中高纬地区一般在春末和夏季存在准零风层结构;而中低纬过渡区域是否有准零风层结构存在还与准两年震荡(QBO)有关,在QBO东风相位时,过渡区域呈现的特性偏向于中纬特性,在QBO西风相位时,过渡区域呈现的特性偏向于低纬特性.准零风层随经度变化非常小,零风线所在高度随经度的变化幅度一般不超过2 km,过渡区域的变化幅度相对大些.

The characteristics of the stratospheric quasi-zero wind layer and its seasonal and geographic variation features over China are obtained by using the ERA-40 reanalyzed wind data which are provided by ECMWF. Results show that quasi-zero wind layer generally exists at the height range of 18-25 km and some variation of the height of the zero wind line would happen when the time or location change. According to the latitudinal variation of the quasi-zero wind layer, the atmosphere over China could be divided into three parts to discuss its features： low-latitude area （5°N-20°N）, transition area （20°N-32.5°N）, middle- and high-latitude area （32.5°N-55°N）. The quasi-zero wind layer may exist in winter and at the beginning of spring in low-latitude area. In middle- and high- latitude area, the quasi-zero wind layer may be found at the end of spring and in summer. The quasi-zero wind layer in transition area relates to the equatorial quasi-biennial oscillation （QBO）. During the easterly phase of QBO, the characteristics of the transition area are similar to that of the middle-latitude area, while during the westerly phase of QBO, its characteristics are similar to that of the low-latitude area. The quasi-zero wind layer varies little with the longitude. The longitudinal variation of the height of zero wind line may not exceed 2 km. However, this variation is relatively larger in the transition area.