Using non-commercial satellite data to investigate methane emissions in the northeastern provinces and the Iran-Turkmenistan border

Atmospheric methane, as the second most important greenhouse gas after carbon dioxide, plays a significant role in intensifying the greenhouse effect and climate change. In this study, spatial, seasonal, and altitudinal variations of methane concentration and flux in the Khorasan region and the border areas of Iran and Turkmenistan were analyzed using Sentinel-5, AIRS, and MethaneSAT satellite data. The main objective of this study is to analyze the temporal and spatial patterns of methane emissions and to quantify atmospheric methane concentrations derived from satellite observations in the study area. Analysis of the 2023 data showed that the lowest standard deviation of methane concentrations occurred in summer, with a value of 9.5 ppb, whereas the highest standard deviation, approximately 12 ppb, was observed in autumn. In addition, the average methane concentrations in winter, spring, summer, and autumn were estimated at 1883, 1879, 1907, and 1899 ppb, respectively. Furthermore, a comparison between the spatial distribution of seasonal mean atmospheric methane concentrations and seasonal mean wind speed and direction maps showed that higher methane concentrations are associated with weaker wind fields in certain areas. Based on linear regression of annual mean methane values obtained from the AIRS sensor at 500 hPa, methane concentration is increasing at an average rate of 6.55 ppb per year in the region. Finally, analysis of methane flux data from the MethaneSAT satellite indicated that elevated methane fluxes in the Sarakhs area, along the Iran–Turkmenistan border, and near major gas transmission lines suggest significant leakage and warrant further investigation.