How bias correction goes wrong: measurement of X<sub>CO<sub>2</sub></sub> affected by erroneous surface pressure estimates
<p>All measurements of X<sub>CO<sub>2</sub></sub> from space have systematic errors. To reduce a large fraction of these errors, a bias correction is applied to X<sub>CO<sub>2</sub></sub> retrieved from GOSAT and OCO-2 spectra using the ACOS r...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2019-04-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/12/2241/2019/amt-12-2241-2019.pdf |
| _version_ | 1818178541476380672 |
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| author | M. Kiel C. W. O'Dell B. Fisher A. Eldering R. Nassar C. G. MacDonald P. O. Wennberg P. O. Wennberg |
| author_facet | M. Kiel C. W. O'Dell B. Fisher A. Eldering R. Nassar C. G. MacDonald P. O. Wennberg P. O. Wennberg |
| author_sort | M. Kiel |
| collection | DOAJ |
| description | <p>All measurements of X<sub>CO<sub>2</sub></sub> from space have systematic errors. To
reduce a large fraction of these errors, a bias correction is applied to
X<sub>CO<sub>2</sub></sub> retrieved from GOSAT and OCO-2 spectra using the ACOS
retrieval algorithm. The bias correction uses, among other parameters, the
surface pressure difference between the retrieval and the meteorological
reanalysis. Relative errors in the surface pressure estimates, however,
propagate nearly 1:1 into relative errors in bias-corrected
X<sub>CO<sub>2</sub></sub>. For OCO-2, small errors in the knowledge of the pointing
of the observatory (up to ∼ 130 arcsec) introduce a bias in
X<sub>CO<sub>2</sub></sub> in regions with rough topography. Erroneous surface
pressure estimates are also caused by a coding error in ACOS version 8,
sampling meteorological analyses at wrong times (up to 3 h after the
overpass time). Here, we derive new geolocations for OCO-2's eight footprints
and show how using improved knowledge of surface pressure estimates in the
bias correction reduces errors in OCO-2's v9 X<sub>CO<sub>2</sub></sub> data.</p> |
| first_indexed | 2024-12-11T20:49:37Z |
| format | Article |
| id | doaj.art-ecbafcff52a94bfea72b6d69017d4490 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-12-11T20:49:37Z |
| publishDate | 2019-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-ecbafcff52a94bfea72b6d69017d44902022-12-22T00:51:17ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482019-04-01122241225910.5194/amt-12-2241-2019How bias correction goes wrong: measurement of X<sub>CO<sub>2</sub></sub> affected by erroneous surface pressure estimatesM. Kiel0C. W. O'Dell1B. Fisher2A. Eldering3R. Nassar4C. G. MacDonald5P. O. Wennberg6P. O. Wennberg7Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USAColorado State University, Fort Collins, CO, USAJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USAJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USAClimate Research Division, Environment and Climate Change Canada, Toronto, ON, CanadaDepartment of Physics and Astronomy, University of Waterloo, Waterloo, ON, CanadaDivision of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USADivision of Engineering and Applied Sciences, California Institute of Technology, Pasadena, CA, USA<p>All measurements of X<sub>CO<sub>2</sub></sub> from space have systematic errors. To reduce a large fraction of these errors, a bias correction is applied to X<sub>CO<sub>2</sub></sub> retrieved from GOSAT and OCO-2 spectra using the ACOS retrieval algorithm. The bias correction uses, among other parameters, the surface pressure difference between the retrieval and the meteorological reanalysis. Relative errors in the surface pressure estimates, however, propagate nearly 1:1 into relative errors in bias-corrected X<sub>CO<sub>2</sub></sub>. For OCO-2, small errors in the knowledge of the pointing of the observatory (up to ∼ 130 arcsec) introduce a bias in X<sub>CO<sub>2</sub></sub> in regions with rough topography. Erroneous surface pressure estimates are also caused by a coding error in ACOS version 8, sampling meteorological analyses at wrong times (up to 3 h after the overpass time). Here, we derive new geolocations for OCO-2's eight footprints and show how using improved knowledge of surface pressure estimates in the bias correction reduces errors in OCO-2's v9 X<sub>CO<sub>2</sub></sub> data.</p>https://www.atmos-meas-tech.net/12/2241/2019/amt-12-2241-2019.pdf |
| spellingShingle | M. Kiel C. W. O'Dell B. Fisher A. Eldering R. Nassar C. G. MacDonald P. O. Wennberg P. O. Wennberg How bias correction goes wrong: measurement of X<sub>CO<sub>2</sub></sub> affected by erroneous surface pressure estimates Atmospheric Measurement Techniques |
| title | How bias correction goes wrong: measurement of X<sub>CO<sub>2</sub></sub> affected by erroneous surface pressure estimates |
| title_full | How bias correction goes wrong: measurement of X<sub>CO<sub>2</sub></sub> affected by erroneous surface pressure estimates |
| title_fullStr | How bias correction goes wrong: measurement of X<sub>CO<sub>2</sub></sub> affected by erroneous surface pressure estimates |
| title_full_unstemmed | How bias correction goes wrong: measurement of X<sub>CO<sub>2</sub></sub> affected by erroneous surface pressure estimates |
| title_short | How bias correction goes wrong: measurement of X<sub>CO<sub>2</sub></sub> affected by erroneous surface pressure estimates |
| title_sort | how bias correction goes wrong measurement of x sub co sub 2 sub sub affected by erroneous surface pressure estimates |
| url | https://www.atmos-meas-tech.net/12/2241/2019/amt-12-2241-2019.pdf |
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