中文摘要：

AC-FTS（加拿大“大气化学实验”的傅里叶变换光谱仪）和Aura-MLS（美国Aura卫星的微波临边探测器）卫星CO观测资料的分析结果显示，南北半球极区大气平流层中部，于当地冬末春初季节存在明显的CO浓度垂直分布次峰值现象。应用观测密度较大、范围覆盖较广的Aura-MLS卫星资料，通过对冬春季节极区CO浓度的季节内变化进行分析后发现，冬季来自大气中间层富含CO的空气能够逐渐下沉并进入到平流层中部，在冬末春初时节，平流层上部的CO浓度快速下降，而平流层中部的CO浓度变化则较慢，从而使大气平流层中CO浓度呈现悬球状的空间分布结构，卫星观测廓线资料分析结果则呈现出次峰值现象。相应的同化气象数据MERRA的风场资料和Aura．MLS卫星观测OH资料分析结果表明，垂直输送的减弱、水平交换的加强和OH浓度的回升可能是导致平流层上部CO浓度快速减少的原因，而在平流层中部极低的OH浓度以及极弱的水平交换使CO保持较长的化学寿命，并使这一现象得以从晚冬维持到春季。

英文摘要：

Analysis of CO from spacebome ACE-FTS （Atmospheric Chemistry Experiment, Fourier Transform Spectrometer） and Aura-MLS （Aura satellite, Microwave Limb Sounder） satellite observations highlights the existence of a sub-peak in CO profiles from late winter to early spring in the polar regions of both the northern and southern hemispheres at the 10 hPa level （i.e., in the middle of the stratosphere）. Further analysis of Aura-MLS satellite data demonstrates that air from the mesosphere, which is rich in CO, descends into the stratosphere gradually in early winter. Moreover, while the CO concentration in the upper stratosphere decreases rapidly during late winter, CO concentration in the middle stratosphere changes very slowly. This results in the dramatic emergence of a suspended spherical structure inthe stratosphere, defined by high CO concentrations; the satellite observation shows such a sub-peak in the CO concentration profiles. Analysis of the MERRA （the Modem Era Retrospective-analysis for Research and Applications） assimilated data and OH concentrations from Aura-MLS satellite observations suggests that weakening of vertical transport from the mesosphere to stratosphere, enhancement of horizontal exchange, and recovery of the OH concentration may play important roles in reducing CO concentration in the upper stratosphere. However, CO in the middle stratosphere can survive for a relatively long time owing to both the isolation imposed by the transport barrier and the lower OH concentration in the polar regions, thus allowing the sub-peak to persist from late winter to spring.