The operational methane retrieval algorithm for TROPOMI

Hu, Haili; Hasekamp, Otto; Butz, André; Galli, André; Landgraf, Jochen; Aan de Brugh, Joost; Borsdorff, Tobias; Scheepmaker, Remco; Aben, Ilse (2016). The operational methane retrieval algorithm for TROPOMI. Atmospheric Measurement Techniques (AMT), 9(11), pp. 5423-5440. Copernicus Publications 10.5194/amt-9-5423-2016

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This work presents the operational methane retrieval algorithm for the Sentinel 5 Precursor (S5P) satellite and its performance tested on realistic ensembles of simulated measurements. The target product is the column-averaged dry air volume mixing ratio of methane (XCH4), which will be retrieved simultaneously with scattering properties of the atmosphere. The algorithm attempts to fit spectra observed by the shortwave and near-infrared channels of the TROPOspheric Monitoring Instrument (TROPOMI) spectrometer aboard S5P. The sensitivity of the retrieval performance to atmospheric scattering properties, atmospheric input data and instrument calibration errors is evaluated. In addition, we investigate the effect of inhomogeneous slit illumination on the instrument spectral response function. Finally, we discuss the cloud filters to be used operationally and as backup. We show that the required accuracy and precision of  < 1 % for the XCH4 product are met for clear-sky measurements over land surfaces and after appropriate filtering of difficult scenes. The algorithm is very stable, having a convergence rate of 99 %. The forward model error is less than 1 % for about 95 % of the valid retrievals. Model errors in the input profile of water do not influence the retrieval outcome noticeably. The methane product is expected to meet the requirements if errors in input profiles of pressure and temperature remain below 0.3 % and 2 K, respectively. We further find that, of all instrument calibration errors investigated here, our retrievals are the most sensitive to an error in the instrument spectral response function of the shortwave infrared channel.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences

UniBE Contributor:

Galli, André

Subjects:

500 Science > 520 Astronomy
500 Science > 530 Physics
600 Technology > 620 Engineering

ISSN:

1867-1381

Publisher:

Copernicus Publications

Language:

English

Submitter:

Katharina Weyeneth-Moser

Date Deposited:

06 Jul 2017 11:17

Last Modified:

06 Jul 2017 11:17

Publisher DOI:

10.5194/amt-9-5423-2016

BORIS DOI:

10.7892/boris.97582

URI:

https://boris.unibe.ch/id/eprint/97582

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