Spatiotemporal Investigation of Near-Surface CO₂ and Its Affecting Factors Over Asia

In this work, we extracted the near-surface CO ₂ concentration from the Greenhouse gases Observing SATellite (GOSAT) and the National Oceanic and Atmospheric Administration (NOAA) CarbonTracker model datasets for a temporal period of eight years from 2010 to 2017 to study the spatiotemporal distribution of near-surface CO ₂ and the factors affecting it over five regions of Asia, including Central Asia, East Asia, South Asia, Southeast Asia, and West Asia. The near-surface CO ₂ datasets from both satellite and model were first validated against the ground-based CO ₂ observations obtained from the World Data Center for Greenhouse Gases (WDCGG) stations located in Asia to confirm their applicability, and the results showed a good agreement between the datasets with significant correlations. The results from the time-series analyses showed a gradual increase in the near-surface CO ₂ with significant monthly and seasonal variations over all the regions. To study the factors affecting the spatial distribution of near-surface CO ₂ , we investigated the relationship of near-surface CO ₂ with the anthropogenic CO ₂ emissions, terrestrial ecosystem, and winds. The results showed that, over Asia, the anthropogenic CO ₂ emissions and winds primarily controlled the spatial distribution of near-surface CO ₂ . However, in the areas where anthropogenic emissions were lower, the terrestrial ecosystem and winds affected the near-surface CO ₂ distribution. To study the factors controlling the temporal distribution of near-surface CO ₂ , the relationship of near-surface CO ₂ with vegetation, precipitation, and relative humidity was investigated. The results showed an inverse relationship between near-surface CO ₂ and normalized difference vegetation index (NDVI), precipitation, and relative humidity over monsoon-influenced regions, i.e., East Asia, South Asia, and Southeast Asia. However, a positive relation of near-surface CO ₂ was observed with precipitation and relative humidity over arid and semiarid regions, i.e., Central Asia and West Asia. The results were also verified by determining the correlations among these variables.