Recovery and validation of Odin/SMR long-term measurements of mesospheric carbon monoxide
Journal article, 2020

The Sub-Millimetre Radiometer (SMR) on board the Odin satellite performs limb sounding measurements of the middle atmosphere to detect molecular emission from different species. Carbon monoxide (CO) is an important tracer of atmospheric dynamics at these altitudes, due to its long photochemical lifetime and high vertical concentration gradient. In this study, we have successfully recovered over 18 years of SMR observations, providing the only dataset to date being so extended in time and stretching out to the polar regions, with regards to satellite-measured mesospheric CO. This new dataset is part of the Odin/SMR version 3.0 level 2 data. Much of the level 1 dataset - except the October 2003 to October 2004 period - was affected by a malfunctioning of the phase-lock loop (PLL) in the front end used for CO observations. Because of this technical issue, the CO line could be shifted away from its normal frequency location, causing the retrieval to fail or leading to an incorrect estimation of the CO concentration. An algorithm was developed to locate the CO line and shift it to its correct location. Nevertheless, another artefact causing an underestimation of the concentration, i.e. a line broadening, stemmed from the PLL malfunctioning. This was accounted for by using a broader response function. The application of these corrections resulted in the recovery of a large amount of data that was previously being flagged as problematic and therefore not processed. A validation study has been carried out, showing how SMR CO volume mixing ratios are in general in good accordance with the other instruments considered in the study. Overall, the agreement is very good between 60 and 80 km altitude, with relative differences close to zero. A positive bias at low altitudes (50-60 km) up to +20% and a negative bias up to -20% at high altitudes (80-100 km) were found with respect to the comparison instruments.

Author

Francesco Grieco

Chalmers, Space, Earth and Environment, Microwave and Optical Remote Sensing

Kristell Perot

Chalmers, Space, Earth and Environment, Microwave and Optical Remote Sensing

Donal Murtagh

Chalmers, Space, Earth and Environment, Microwave and Optical Remote Sensing

Patrick Eriksson

Chalmers, Space, Earth and Environment, Microwave and Optical Remote Sensing

Peter Forkman

Chalmers, Space, Earth and Environment, Onsala Space Observatory, Space Geodesy and Geodynamics

Bengt Rydberg

Molflow AB

Bernd Funke

Spanish National Research Council (CSIC)

Kaley A. Walker

University of Toronto

Hugh C. Pumphrey

University of Edinburgh

Atmospheric Measurement Techniques

1867-1381 (ISSN) 1867-8548 (eISSN)

Vol. 13 9 5013-5031

Odin

Swedish National Space Board, 2015-01-01 -- 2017-12-31.

European Space Agency (ESA), 2015-09-01 -- 2017-08-31.

Subject Categories

Meteorology and Atmospheric Sciences

Atom and Molecular Physics and Optics

Physical Geography

DOI

10.5194/amt-13-5013-2020

More information

Latest update

11/10/2020