Analysis of the Spatiotemporal Distribution Pattern of Mid-Tropospheric CO 2 and Its Driving Forces over Central Asia During 2003–2011

Carbon dioxide (CO2), the major anthropogenic greenhouse gas, plays a critical role in climate change. Using Atmospheric Infrared Sounder (AIRS) CO2 retrievals and auxiliary datasets, this study investigated the spatiotemporal characteristics of mid-tropospheric CO2 and its driving factors over Central Asia during 2003–2011. Pixel-based linear trend analysis, empirical orthogonal function (EOF), singular value decomposition (SVD), and correlation analysis were applied. The results show that mid-tropospheric CO2 exhibited a distinct low-high-low spatial pattern from north to south across Central Asia. Low-CO2 centers were mainly associated with vegetation and terrain, whereas high-CO2 centers were related to land surface type, atmospheric circulation, and topography. Mid-tropospheric CO2 increased at an average rate of 2.1 ppm yr−1 during the study period. Pronounced seasonal fluctuations were also observed, primarily driven by seasonal variations in carbon exchange between terrestrial ecosystems and the atmosphere. In addition, the response of mid-tropospheric CO2 to seasonal carbon exchange showed an approximately four-month lag. These findings provide a regional perspective on the distribution, trend, and seasonal dynamics of mid-tropospheric CO2 over Central Asia and improve understanding of CO2 variability in arid inland regions influenced by long-range atmospheric transport.