|Paper title||Quantification of local methane emissions over Middle East with TROPOMI|
|Form of presentation||Poster|
Methane (CH4) is the second most important greenhouse gas, of which more than 60 % CH4 is released through human activities. Satellite observations of CH4 provide an efficient way to analyze its variations and emissions. The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel 5 Precursor (S5-P) satellite measures CH4 at a high horizontal resolution of 7 × 7 km2, showing the capability of identifying and quantifying the sources at a local to regional scale. The Middle East is one of the strong CH4 hotspot regions in the world. However, it is difficult to estimate the emissions here because several sources are located near the coast or in places with complex topography, where the satellite observations are often of reduced quality. We use the WMF-DOAS XCH4 v1.5 product, which has good spatial coverage over the ocean and mountains, to better estimate the emissions in the Middle East.
The divergence method of Liu et al., (2021) has been proven to be a fast and efficient way to estimate CH4 emissions from satellite observations. We have improved our method by comparing the fluxes in different directions for better background corrections over areas with complicated topographies. The performance of the updated algorithm was tested by comparing the estimated emissions from a 1-month WRF-CMAQ model simulation with its known emission inventory over the Middle East. The CH4 emissions based on TROPOMI XCH4 are then derived on a 0.25° grid for 2019 and 2020. With the WMF-DOAS product, sources from oil/gas platforms over the Persian Gulf and sources on the west coast of Turkmenistan become clearly visible in the emission maps. Sources in the mountain areas of Iran are also identified by our updated divergence method. The locations of fossil fuel related NOX emissions usual overlap with CH4 emissions as can be seen in the CAMS bottom-up inventory. Therefore, we have compared our CH4 emission inventory with the emissions derived from TROPOMI observed NO2, in order to gain more insight into the source of the emissions, especially concerning the oil/gas industry in the region.