Using OCO-2 satellite data for investigating the variability of atmospheric CO₂ concentration in relationship with precipitation, relative humidity, and vegetation over Oman

Recognition of the carbon dioxide (CO₂) concentration variations over time is critical for tracing the future changes in climate both globally and regionally. In this study, a time series analysis of atmospheric CO₂ concentration and its relationship with precipitation, relative humidity (RH), and vegetation is investigated over Oman. The daily XCO₂ data from OCO-2 satellite was obtained from September 2014 to March 2019. The daily RH and precipitation data were also collected from the ground weather stations, and the Normalized Difference Vegetation Index was obtained from MODIS. Oman was studied in four distinct regions where the main emphasis was on the Monsoon Region in the far south. The CO₂ concentration time series indicated a significant upward trend over different regions for the study period, with annual cycles being the same for all regions except the Monsoon Region. This is indicative of RH, precipitation, and consequently vegetation cover impact on atmospheric CO₂ concentration, resulting in an overall lower annual growth in the Monsoon Region. Simple and multiple correlation analyses of CO₂ concentration with mentioned parameters were performed in zero to three-month lags over Oman. They showed high correlations mainly during the rainfall period in the Monsoon Region.