Anthropogenic and volcanic point source SO<sub>2</sub> emissions derived from TROPOMI onboard Sentinel 5 Precursor: first results

Abstract

<p><strong>Abstract.</strong> The paper introduces the first TROPOMI-based sulfur dioxide (SO<sub>2</sub>) emissions estimates for point sources. A total of about 500 continuously emitting point sources releasing from about 10 kT y<sup>−1</sup> to more than 2000 kT y<sup>−1</sup> of SO<sub>2</sub> per year, previously identified from Ozone Monitoring Instrument (OMI) observations, were analysed using TROPOMI measurements for one full year, from April 2018 to March 2019. The annual emissions from these sources were estimated and compared to similar estimates from OMI and Ozone Mapping Profiling Suite (OMPS) measurements. Note that emissions from many of these 500 sources declined significantly since 2005 making their quantification more challenging. We were able to identify 278 sources where annual emissions are significant and can be reliably estimated from TROPOMI. The standard deviations of TROPOMI vertical column density data, about 1 Dobson Unit (DU, where 1 DU = 2.69 × 10<sup>16</sup> molecules/cm<sup>2</sup>) over tropics and 1.5 DU over high latitudes, are larger than those of OMI (0.6–1 DU) and OMPS (0.3–0.4 DU). Due to its very high spatial resolution, TROPOMI produces 12–20 times more observations over a certain area than OMI and 96 times more than OMPS. Despite higher uncertainties of individual TROPOMI observations, TROPOMI data averaged over a large area have roughly two-three times lower uncertainties compared to OMI and OMPS data. Similarly, TROPOMI annual emissions can be estimated with uncertainties that are 1.5–2 times lower than the uncertainties of annual emissions estimates from OMI. While there are area biases in TROPOMI data over some regions that have to be removed for emission calculations, the absolute magnitude of these are modest, typically within ±0.25 DU, it can be comparable to SO<sub>2</sub> values over large sources.</p>

Version 2 of the global catalogue of large anthropogenic and volcanic SO2 sources and emissions derived from satellite measurements

“…Typical standard deviations of the individual OMI VCDs over background areas are between 0.6 DU in the tropics and 1 DU at high latitudes. The same values for OMPS are 0.3-0.4 DU (Fioletov et al, 2020).…”

“…The instrument consists of UV-VIS-NIR spectrometers and SO 2 can be retrieved from the UV part of the measured spectra. The TROPOMI detector has 450 cross-track positions, however the first and last 20 of them were excluded from our analysis due to a relatively high noise level (Fioletov et al, 2020). The spatial resolution for the centre of the swath was originally 3.5 km × 7 km (along track) and it was reduced to 3.5 km × 5.5 km after August 6, 2019.…”

“…Satellite SO 2 measurements by the Ozone Mapping and Profiler Suite (OMPS) (Zhang et al, 2017) on the NASA-NOAA Suomi National Polar-orbiting Partnership (SNPP) spacecraft (Flynn et al, 2014;Seftor et al, 2014) and by the TROPOspheric Monitoring Instrument (TROPOMI) (Theys et al, 2017) on the ESA Copernicus Sentinel-5 Precursor (S-5P) spacecraft (Veefkind et al, 2012) became available starting in 2012 and 2018, respectively. Their measurements are suitable for SO 2 emissions estimates and can provide additional inputs for the SO 2 catalogue (Fioletov et al, 2020;Theys et al, 2021;Zhang et al, 2017). A newer European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5) reanalysis version (C3S, 2017) provides wind data with a higher spatial and temporal resolution than the ERA-Interim reanalysis (Dee et al, 2011) used in the original SO 2 catalogue.…”

The Airborne ROmanian Measurements of Aerosols and Trace gases (AROMAT) campaigns

“…VCDs detected above Turceni on 28 August 2015 are expectedly higher than for standard conditions, all the more so as the SO 2 VCDs in the area seem to have further decreased (D. Constantin, personnal communication). The first reported TROPOMI SO 2 measurements above the area pinpoint other power plants in Serbia, Bosnia-Herzegovina, and Bulgaria (Fioletov et al, 2020). For validation studies, it would be worth to install automatic SO 2 cameras around these plants, until they are equiped with FGD units.…”

Evaluation of the accuracy of the Sentinel-5 Precursor operational SO<sub>2</sub> products over China

“…但是欧洲业务SO 2 数据标志了更大范围的 污染, 与其他卫星数据和我国SO 2 大幅减 排的事实相悖 [11] . Fioletov等人 [23] 在计算 TROPOMI仪器响应函数v3.0.0 [19] 地表反射率 OMI月平均气候统计数据 [20] 云 哨兵5号二级云产品数据 [10] 反演波段 312~326 nm 310.5~326 nm SO 2 先验廓线 TM5模拟每日廓线 [15] GEOS-Chem模拟月平均廓线 [20] SO 2 吸收截面 203 K [21] 203, 223, 243, 273, 293 K [21] O 3 吸收截面 228, 243 K [22] 218, 228, 243, 295 K [22] 低阶多项式 5 无…”