中层大气静力稳定性减弱趋势——历史火箭探空数据分析

大气静力稳定性参数Brunt-Vaisala频率反映了以温度垂直梯度为代表的大气整体结构的特征. 全球增暖背景下, 学术界对中层大气静力稳定性的响应形式还相当缺乏了解. 利用历史火箭探空资料, 考察了1962–1991年期间从赤道到北半球中纬度地区中层大气静力稳定性(Brunt-Vaisala频率的平方, N²)的长期趋势. 结果表明, 对于选取的6个典型站点, 在平流 层上部到中间层中部区域(48–60 km), 所有站点大气静力稳定性一致呈现显著减弱的长期趋势. 48–60 km整层平均N²长期趋势统计结果表明, 在两个热带站点, N²长期趋势一致, 每十年减小0.11×10^-4 s^-2; 随着纬度增加, 在从22°N (Barking Sand 站)向38°N (Wallops Island 站)过渡的区间内, N²趋势从-0.16×10^-4 s^-2/decade增强到-0.22×10^-4 s^-2/decade.

Decreasing trend of the middle atmospheric static stability in historical data from rocketsonde network

Brunt-Vaisala frequency squared (N²) measures the static stability of the atmosphere, and reflects the general structure of the atmosphere in term of vertical temperature gradient. For middle atmosphere the response of the middle atmospheric structure to the global warming still lacks investigation currently. The historical data from rocket sounding network in 1962-1991 are used to investigate the long-term trend of N² in the middle atmosphere. For six stations spanning from the tropical latitudes to the northern mid-latitudes, our estimates show that, in the upper stratosphere and middle mesosphere, i. e., 48-60 km high, the significant decreasing of static stability is observed in an N² anomalies averaged over 48-60 km range. For two tropical stations, long-term trend in N² exhibits a similar magnitude, i.e., -0.11×10^-4 s^-2/decade; it is also observed that the trend increases with latitude, with trend estimates from -0.16×10^-4 s^-2/decade at 22°N (Barking Sand station) to -0.22×10^-4 s^-2/decade at 38°N (Wallops Island station).