Improvement of OMI ozone profile retrievals by simultaneously fitting polar mesospheric clouds
The presence of polar mesospheric clouds (PMCs) at summer high latitudes could affect the retrieval of ozone profiles using backscattered ultraviolet (UV) measurements. PMC-induced errors in ozone profile retrievals from Ozone Monitoring Instrument (OMI) backscattered UV measurements are investigate...
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2016-09-01
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doaj-ca3b3831ea5545909560371709e8f8582020-11-24T23:25:36ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482016-09-01994521453110.5194/amt-9-4521-2016Improvement of OMI ozone profile retrievals by simultaneously fitting polar mesospheric cloudsJ. Bak0X. Liu1J. H. Kim2M. T. Deland3K. Chance4Pusan National University, Department of Atmospheric Sciences, Busan, South KoreaHarvard-Smithsonian Center for Astrophysics, Cambridge, MA, USAPusan National University, Department of Atmospheric Sciences, Busan, South KoreaSystems and Applications, Inc. (SSAI), 10210 Greenbelt Rd., Suite 600, Lanham, MD 20706, USAHarvard-Smithsonian Center for Astrophysics, Cambridge, MA, USAThe presence of polar mesospheric clouds (PMCs) at summer high latitudes could affect the retrieval of ozone profiles using backscattered ultraviolet (UV) measurements. PMC-induced errors in ozone profile retrievals from Ozone Monitoring Instrument (OMI) backscattered UV measurements are investigated through comparisons with Microwave Limb Sounder (MLS) ozone measurements. This comparison demonstrates that the presence of PMCs leads to systematic biases for pressures smaller than 6 hPa; the biases increase from ∼ −2 % at 2 hPa to ∼ −20 % at 0.5 hPa on average and are significantly correlated with brightness of PMCs. Sensitivity studies show that the radiance sensitivity to PMCs strongly depends on wavelength, increasing by a factor of ∼ 4 from 300 to 265 nm. It also strongly depends on the PMC scattering, thus depending on viewing geometry. The optimal estimation-based retrieval sensitivity analysis shows that PMCs located at 80–85 km have the greatest effect on ozone retrievals at ∼ 0.2 hPa ( ∼ 60 km), where the retrieval errors range from −2.5 % with PMC vertical optical depth (POD) of 10<sup>−4</sup> to −20 % with 10<sup>−3</sup> POD at backscattering angles. The impacts increase by a factor of ∼ 5 at forward-scattering angles due to stronger PMC sensitivities. To reduce the interference of PMCs on ozone retrievals, we perform simultaneous retrievals of POD and ozone with a loose constraint of 10<sup>−3</sup> for POD, which results in retrieval errors of 1–4 × 10<sup>−4</sup>. It is demonstrated that the negative bias of OMI ozone retrievals relative to MLS can be improved by including the PMC in the forward-model calculation and retrieval.http://www.atmos-meas-tech.net/9/4521/2016/amt-9-4521-2016.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
J. Bak X. Liu J. H. Kim M. T. Deland K. Chance |
spellingShingle |
J. Bak X. Liu J. H. Kim M. T. Deland K. Chance Improvement of OMI ozone profile retrievals by simultaneously fitting polar mesospheric clouds Atmospheric Measurement Techniques |
author_facet |
J. Bak X. Liu J. H. Kim M. T. Deland K. Chance |
author_sort |
J. Bak |
title |
Improvement of OMI ozone profile retrievals by simultaneously fitting polar
mesospheric clouds |
title_short |
Improvement of OMI ozone profile retrievals by simultaneously fitting polar
mesospheric clouds |
title_full |
Improvement of OMI ozone profile retrievals by simultaneously fitting polar
mesospheric clouds |
title_fullStr |
Improvement of OMI ozone profile retrievals by simultaneously fitting polar
mesospheric clouds |
title_full_unstemmed |
Improvement of OMI ozone profile retrievals by simultaneously fitting polar
mesospheric clouds |
title_sort |
improvement of omi ozone profile retrievals by simultaneously fitting polar
mesospheric clouds |
publisher |
Copernicus Publications |
series |
Atmospheric Measurement Techniques |
issn |
1867-1381 1867-8548 |
publishDate |
2016-09-01 |
description |
The presence of polar mesospheric clouds (PMCs) at summer high latitudes
could affect the retrieval of ozone profiles using backscattered ultraviolet
(UV) measurements. PMC-induced errors in ozone profile retrievals from Ozone
Monitoring Instrument (OMI) backscattered UV measurements are investigated
through comparisons with Microwave Limb Sounder (MLS) ozone measurements.
This comparison demonstrates that the presence of PMCs leads to systematic
biases for pressures smaller than 6 hPa; the biases increase from
∼ −2 % at 2 hPa to ∼ −20 % at 0.5 hPa on average and are
significantly correlated with brightness of PMCs. Sensitivity studies show
that the radiance sensitivity to PMCs strongly depends on wavelength,
increasing by a factor of ∼ 4 from 300 to 265 nm. It also strongly
depends on the PMC scattering, thus depending on viewing geometry. The
optimal estimation-based retrieval sensitivity analysis shows that PMCs
located at 80–85 km have the greatest effect on ozone retrievals at
∼ 0.2 hPa ( ∼ 60 km), where the retrieval errors range from
−2.5 % with PMC vertical optical depth (POD) of 10<sup>−4</sup> to
−20 % with 10<sup>−3</sup> POD at backscattering angles. The impacts
increase by a factor of ∼ 5 at forward-scattering angles due to
stronger PMC sensitivities. To reduce the interference of PMCs on ozone
retrievals, we perform simultaneous retrievals of POD and ozone with a loose
constraint of 10<sup>−3</sup> for POD, which results in retrieval errors of
1–4 × 10<sup>−4</sup>. It is demonstrated that the negative bias of OMI
ozone retrievals relative to MLS can be improved by including the PMC in the
forward-model calculation and retrieval. |
url |
http://www.atmos-meas-tech.net/9/4521/2016/amt-9-4521-2016.pdf |
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