Assessment of seasonal variations of carbon dioxide concentration in Iran using GOSAT data

Global warming and climate change have been identified as the most important challenges of the 21st century. Greenhouse Gases Observation Satellite (GOSAT) measures the concentrations of carbon dioxide (CO ₂) and methane (CH ₄) in the atmosphere column from the earth's surface to the upper atmosphere. In this research, GOSAT Thermal And Near Infrared Sensor for Carbon Observation – Fourier Transform Spectrometer (TANSO‐FTS) level 2 data and meteorological parameters were used in the assessment of changes in CO ₂ concentration (XCO ₂) from 2009 to 2015. We investigated the relationship between XCO ₂ and meteorological parameters (temperature and precipitation) obtained from weather stations and the Normalized Difference Vegetation Index (NDVI) in the year 2013 in Iran. The results reveal a steady increase in the mean atmospheric CO ₂ concentration, from 384.89 to 400.39 ppm. It was observed that the XCO ₂ varied significantly depending on the month, with the highest concentration of CO ₂ in April/May and the lowest concentration in August/September. The correlation between XCO ₂ and average monthly air temperature is negative, which means that a reduction in XCO ₂ with an increase in temperature is dependent on photosynthetic activities in the growing seasons. The highest and lowest correlation coefficient between the NDVI and XCO ₂ was obtained in the spring and in the fall, respectively. These findings are useful for recognizing factors that affect CO ₂ concentration in different seasons in arid and semi‐arid regions, and as an initial step toward sustainable management.