Solar occultation measurement of mesospheric ozone by SAGE III/ISS: impact of variations along the line of sight caused by photochemistry
<p>Twilight gradients in the concentration of atmospheric species with short photochemical lifetimes influence the transmission data obtained in a solar occultation instrument, such as the Stratospheric Aerosol and Gas Experiment III aboard the International Space Station (SAGE III/ISS). These...
| Main Authors: | , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-01-01
|
| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/16/75/2023/amt-16-75-2023.pdf |
| _version_ | 1797957105742774272 |
|---|---|
| author | M. Natarajan R. Damadeo D. Flittner |
| author_facet | M. Natarajan R. Damadeo D. Flittner |
| author_sort | M. Natarajan |
| collection | DOAJ |
| description | <p>Twilight gradients in the concentration of atmospheric species
with short photochemical lifetimes influence the transmission data obtained
in a solar occultation instrument, such as the Stratospheric Aerosol and Gas Experiment III aboard the International Space Station (SAGE III/ISS). These photochemically induced changes result in nonlinear asymmetries in the species distribution near the tangent altitude along the line of sight
(LOS). The bias introduced by neglecting the effects of twilight variations
in the retrieval of mesospheric ozone is the focus of this study. Ozone (O<span class="inline-formula"><sub>3</sub></span>) in the mesosphere exhibits large variations near the terminator during sunrise
and sunset based on current understanding of the photochemistry of this
altitude region. The algorithm used in the SAGE III/ISS standard retrieval
procedure for mesospheric ozone does not include the effects of these
gradients. This study illustrates a method for implementing a correction
scheme to account for the twilight variations in mesospheric O<span class="inline-formula"><sub>3</sub></span> and
gives an estimate of the bias in the standard retrieval. We use the results
from a diurnal photochemical model conducted at different altitudes to
develop a database of ratios of mesospheric O<span class="inline-formula"><sub>3</sub></span> at different solar
zenith angles (SZA) around 90<span class="inline-formula"><sup>∘</sup></span> to O<span class="inline-formula"><sub>3</sub></span> at a SZA of
90<span class="inline-formula"><sup>∘</sup></span> for both sunrise and sunset conditions. These ratios are used
to scale the O<span class="inline-formula"><sub>3</sub></span> at levels above the tangent altitude for appropriate
SZA in the calculation of the optical depth along the LOS. In general, the
impact of the corrections due to twilight variations is to increase the
contribution of the overlying layers to the optical depth thereby reducing
the retrieved O<span class="inline-formula"><sub>3</sub></span> concentration at the tangent altitude. We find that
at sunrise the retrieved mesospheric O<span class="inline-formula"><sub>3</sub></span> including the diurnal
corrections is lower by more than 30 % compared to the archived O<span class="inline-formula"><sub>3</sub></span>.
We show the results obtained for different latitudes and seasons. In
addition, for nearly collocated sunrise and sunset scans, we note that these
corrections lead to better qualitative agreement in the sunrise to sunset
O<span class="inline-formula"><sub>3</sub></span> ratio with the photochemical model prediction.</p> |
| first_indexed | 2024-04-10T23:59:04Z |
| format | Article |
| id | doaj.art-8b6ffd6eb08d48f28bc658351bd94ea1 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-04-10T23:59:04Z |
| publishDate | 2023-01-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-8b6ffd6eb08d48f28bc658351bd94ea12023-01-10T06:57:07ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482023-01-0116758710.5194/amt-16-75-2023Solar occultation measurement of mesospheric ozone by SAGE III/ISS: impact of variations along the line of sight caused by photochemistryM. NatarajanR. DamadeoD. Flittner<p>Twilight gradients in the concentration of atmospheric species with short photochemical lifetimes influence the transmission data obtained in a solar occultation instrument, such as the Stratospheric Aerosol and Gas Experiment III aboard the International Space Station (SAGE III/ISS). These photochemically induced changes result in nonlinear asymmetries in the species distribution near the tangent altitude along the line of sight (LOS). The bias introduced by neglecting the effects of twilight variations in the retrieval of mesospheric ozone is the focus of this study. Ozone (O<span class="inline-formula"><sub>3</sub></span>) in the mesosphere exhibits large variations near the terminator during sunrise and sunset based on current understanding of the photochemistry of this altitude region. The algorithm used in the SAGE III/ISS standard retrieval procedure for mesospheric ozone does not include the effects of these gradients. This study illustrates a method for implementing a correction scheme to account for the twilight variations in mesospheric O<span class="inline-formula"><sub>3</sub></span> and gives an estimate of the bias in the standard retrieval. We use the results from a diurnal photochemical model conducted at different altitudes to develop a database of ratios of mesospheric O<span class="inline-formula"><sub>3</sub></span> at different solar zenith angles (SZA) around 90<span class="inline-formula"><sup>∘</sup></span> to O<span class="inline-formula"><sub>3</sub></span> at a SZA of 90<span class="inline-formula"><sup>∘</sup></span> for both sunrise and sunset conditions. These ratios are used to scale the O<span class="inline-formula"><sub>3</sub></span> at levels above the tangent altitude for appropriate SZA in the calculation of the optical depth along the LOS. In general, the impact of the corrections due to twilight variations is to increase the contribution of the overlying layers to the optical depth thereby reducing the retrieved O<span class="inline-formula"><sub>3</sub></span> concentration at the tangent altitude. We find that at sunrise the retrieved mesospheric O<span class="inline-formula"><sub>3</sub></span> including the diurnal corrections is lower by more than 30 % compared to the archived O<span class="inline-formula"><sub>3</sub></span>. We show the results obtained for different latitudes and seasons. In addition, for nearly collocated sunrise and sunset scans, we note that these corrections lead to better qualitative agreement in the sunrise to sunset O<span class="inline-formula"><sub>3</sub></span> ratio with the photochemical model prediction.</p>https://amt.copernicus.org/articles/16/75/2023/amt-16-75-2023.pdf |
| spellingShingle | M. Natarajan R. Damadeo D. Flittner Solar occultation measurement of mesospheric ozone by SAGE III/ISS: impact of variations along the line of sight caused by photochemistry Atmospheric Measurement Techniques |
| title | Solar occultation measurement of mesospheric ozone by SAGE III/ISS: impact of variations along the line of sight caused by photochemistry |
| title_full | Solar occultation measurement of mesospheric ozone by SAGE III/ISS: impact of variations along the line of sight caused by photochemistry |
| title_fullStr | Solar occultation measurement of mesospheric ozone by SAGE III/ISS: impact of variations along the line of sight caused by photochemistry |
| title_full_unstemmed | Solar occultation measurement of mesospheric ozone by SAGE III/ISS: impact of variations along the line of sight caused by photochemistry |
| title_short | Solar occultation measurement of mesospheric ozone by SAGE III/ISS: impact of variations along the line of sight caused by photochemistry |
| title_sort | solar occultation measurement of mesospheric ozone by sage iii iss impact of variations along the line of sight caused by photochemistry |
| url | https://amt.copernicus.org/articles/16/75/2023/amt-16-75-2023.pdf |
| work_keys_str_mv | AT mnatarajan solaroccultationmeasurementofmesosphericozonebysageiiiissimpactofvariationsalongthelineofsightcausedbyphotochemistry AT rdamadeo solaroccultationmeasurementofmesosphericozonebysageiiiissimpactofvariationsalongthelineofsightcausedbyphotochemistry AT dflittner solaroccultationmeasurementofmesosphericozonebysageiiiissimpactofvariationsalongthelineofsightcausedbyphotochemistry |