Quantifying CH4 emissions in hard coal mines from TROPOMI and IASI observations using the wind-assigned anomaly method

Overview & Synopsis

Intensive coal mining activities in the Upper Silesian Coal Basin (USCB) in southern Poland are resulting in large amounts of methane (CH 4 ) emissions. Annual CH 4 emissions reached 448 kt according to the European Pollutant Release and Transfer Register (E-PRTR, 2017). As a CH 4 emission hotspot in Europe, it is of importance to investigate its emission sources and make accurate emission estimates. In this study, we use satellite-based total column-averaged dry-air mole fraction of CH 4 (XCH 4 ) from the TROPOspheric Monitoring Instrument (TROPOMI) and tropospheric XCH 4 (TXCH 4 ) from the Infrared Atmospheric Sounding Interferometer (IASI). In addition, the high-resolution model forecasts, XCH 4 and TXCH 4 , from the Copernicus Atmosphere Monitoring Service (CAMS) are used to estimate the CH 4 emission rate averaged over 3 years (November 2017-December 2020) in the USCB region (49.3-50.8 • N and 18-20 • E). The wind-assigned anomaly method is first validated using the CAMS forecast data (XCH 4 and TXCH 4 ), showing a good agreement with the CAMS GLOBal ANThropogenic emission (CAMS-GLOB-ANT) inventory. It indicates that the wind-assigned method works well. This wind-assigned method is further applied to the TROPOMI XCH 4 and TROPOMI + IASI TXCH 4 by using the Carbon dioxide and Methane (CoMet) inventory derived for the year 2018. The calculated averaged total CH 4 emissions over the USCB region is about 496 kt yr -1 (5.9 × 10 26 molec. s -1 ) for TROPOMI XCH 4 and 437 kt yr -1 (5.2 × 10 26 molec. s -1 ) for TROPOMI + IASI TXCH 4 . These values are very close to the ones given in the E-PRTR inventory (448 kt yr -1 ) and the ones in the CoMet inventory (555 kt yr -1 ), and are thus in agreement with these inventories. The similar estimates of XCH 4 and TXCH 4 also imply that for a strong source, the dynamically induced variations of the CH 4 mixing ratio in the upper troposphere and lower stratosphere region are of secondary importance. Uncertainties from different error sources (background removal and noise in the data, vertical wind shear, wind field segmentation, and angle of the emission cone) are approximately 14.8 % for TROPOMI XCH 4 and 11.4 % for TROPOMI + IASI TXCH 4 . These results suggest that our wind-assigned method is quite robust and might also serve as a simple method to estimate CH 4 or CO 2 emissions for other regions.