A scientific algorithm to simultaneously retrieve carbon monoxide and methane from TROPOMI onboard Sentinel-5 Precursor

Abstract

Carbon monoxide (CO) is an important atmospheric constituent affecting air quality and methane (CH 4 ) is the second most important greenhouse gas contributing to human-induced climate change. Detailed and continuous observations of these gases are necessary to better assess their impact on climate and atmospheric pollution. While surface and airborne measurements are able to accurately determine atmospheric abundances on local scales, global coverage can only be achieved using satellite instruments. 5The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor satellite, which was successfully launched in October 2017, is a spaceborne nadir viewing imaging spectrometer measuring solar radiation reflected by the Earth in a push-broom configuration. It has a wide swath on the terrestrial surface and covers wavelength bands between the ultraviolet (UV) and the shortwave infrared (SWIR) combining a high spatial resolution with daily global coverage. These characteristics enable the determination of both gases with unprecedented level of detail on a global scale introducing new 10 areas of application.Abundances of the atmospheric column-averaged dry air mole fractions XCO and XCH 4 are simultaneously retrieved from TROPOMI's radiance measurements in the 2.3 µm spectral range of the SWIR part of the solar spectrum using the scientific retrieval algorithm Weighting Function Modified DOAS (WFM-DOAS). We introduce the algorithm in detail, including expected error characteristics based on synthetic data, a machine learning-based quality filter and a shallow learning calibration procedure applied in the post-processing of the XCH 4 data. The quality of the results based on real TROPOMI data is assessed 5 by validation with ground-based Fourier Transform Spectrometer (FTS) measurements providing realistic error estimates of the satellite data: The XCO data set is characterised by a random error of 5.1 ppb (5.7%) and a systematic error of 1.9 ppb (2.1%); the XCH 4 data set exhibits a random error of 14.0 ppb (0.8%) and a systematic error of 4.4 ppb (0.2%). The natural XCO and XCH 4 variations are well captured by the satellite retrievals, which is demonstrated by a high correlation to the reference data (R = 0.97 for XCO and R = 0.91 for XCH 4 based on daily averages). 10We also present selected results from mission start until end of 2018, including a first comparison to the operational products and examples of the detection of emission sources in a single satellite overpass, such as CO emissions from the steel industry and CH 4 emissions from the energy sector.

Unexpected long-range transport of glyoxal and formaldehyde observed from the Copernicus Sentinel-5 Precursor satellite during the 2018 Canadian wildfires

“…Reason 3: The plume could contain glyoxal and formaldehyde precursors which slowly produce additional VOCs along the trajectory, resulting in an apparent increase in lifetime. In order to better assess the CHO.CHO and HCHO spatial distribution seen on the 10th of August 2018, two additional S5P retrievals have been taken into account; the column-averaged dry air mole fractions of CO, retrieved by the algorithm described in Schneising et al (2019), and the VCD NO 2 retrieved using an algorithm Tracer distribution simulated with FLEXPART for the same period assuming a lifetime of 28.9 hours. Enhanced CHO.CHO columns spread over the ocean in a pattern similar to that simulated by the model tracer.…”

Widespread Frequent Methane Emissions From the Oil and Gas Industry in the Permian Basin

“…S5P TROPOMI CH 4 mixing ratios are from the Weighting Function Modified Differential Optical Absorption Spectroscopy (WFM‐DOAS) algorithm version 1.5 (Schneising et al., 2019). The main data fields used are the methane column‐averaged dry air mole fraction (XCH4), the surface pressure, the geolocation, and the data quality information.…”