Diurnal variations in the middle atmosphere observed by UARS

Fabrizio Sassi; Murry Salby

doi:10.1029/1998jd100068

Equatorial diurnal variations observed in UARS Microwave Limb Sounder temperature during 1991-1994 and simulated by the Canadian Middle Atmosphere Model

Journal of Geophysical Research Atmospheres ◽

10.1029/98jd00530 ◽

1998 ◽

Vol 103 (D8) ◽

pp. 8909-8917 ◽

Cited By ~ 29

Author(s):

D. L. Wu ◽

C. McLandress ◽

W. G. Read ◽

J. W. Waters ◽

L. Froidevaux

Keyword(s):

Middle Atmosphere ◽

Diurnal Variations ◽

Atmosphere Model

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Accounting for the photochemical variation of stratospheric NO<sub>2</sub> in the SAGE III/ISS solar occultation retrieval

10.5194/amt-2020-331 ◽

2020 ◽

Author(s):

Kimberlee Dubé ◽

Adam Bourassa ◽

Daniel Zawada ◽

Doug Degenstein ◽

Robert Damadeo ◽

...

Keyword(s):

Middle Atmosphere ◽

Space Station ◽

Stratospheric Aerosol ◽

Diurnal Variations ◽

Line Of Sight ◽

Retrieval Algorithm ◽

Number Density ◽

Solar Occultation ◽

Infrared Imager ◽

The Impact

Abstract. The Stratospheric Aerosol and Gas Experiment (SAGE) III has been operating on the International Space Station (ISS) since mid 2017. Nitrogen dioxide (NO2) number density profiles are routinely retrieved from SAGE III/ISS solar occultation measurements in the middle atmosphere. Although NO2 density varies throughout the day due to photochemistry, the standard SAGE NO2 retrieval algorithm neglects these variations along the instrument's line of sight by assuming that the number density has a constant gradient within a given vertical layer of the atmosphere. This assumption will result in a retrieval bias for a species like NO2 that changes rapidly across the terminator. In this work we account for diurnal variations in retrievals of NO2 from the SAGE III/ISS measurements, and determine the impact of this algorithm improvement on the resulting NO2 number densities. The diurnal correction is applied by first undoing the SAGE III/ISS retrieval using publicly available SAGE III/ISS products to obtain an optical depth profile. The retrieval is then performed with a new matrix that applies photochemical scale factors for each point along the line of sight according to the changing solar zenith angle. In general NO2 that is retrieved by accounting for these diurnal variations is more than 10 % lower than the standard algorithm below 30 km. This effect is greatest in winter at high latitudes, and generally greater for sunrise occultations than sunset. Comparisons with coincident profiles from the Optical Spectrograph and InfraRed Imager System (OSIRIS) show that NO2 from SAGE III/ISS is generally biased high, however the agreement improves by up to 20 % in the mid stratosphere when diurnal variations are accounted for in the retrieval. We conclude that diurnal variations along the SAGE III/ISS line of sight are an important term to consider for NO2 analyses at altitudes below 30 km.

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Accounting for the photochemical variation in stratospheric NO<sub>2</sub> in the SAGE III/ISS solar occultation retrieval

Atmospheric Measurement Techniques ◽

10.5194/amt-14-557-2021 ◽

2021 ◽

Vol 14 (1) ◽

pp. 557-566

Author(s):

Kimberlee Dubé ◽

Adam Bourassa ◽

Daniel Zawada ◽

Douglas Degenstein ◽

Robert Damadeo ◽

...

Keyword(s):

Middle Atmosphere ◽

Space Station ◽

Stratospheric Aerosol ◽

Diurnal Variations ◽

Line Of Sight ◽

Retrieval Algorithm ◽

Number Density ◽

Density Profiles ◽

Solar Occultation ◽

The Impact

Abstract. The Stratospheric Aerosol and Gas Experiment (SAGE) III has been operating on the International Space Station (ISS) since mid-2017. Nitrogen dioxide (NO2) number density profiles are routinely retrieved from SAGE III/ISS solar occultation measurements in the middle atmosphere. Although NO2 density varies throughout the day due to photochemistry, the standard SAGE NO2 retrieval algorithm neglects these variations along the instrument's line of sight by assuming that the number density has a constant gradient within a given vertical layer of the atmosphere. This assumption will result in a retrieval bias for a species like NO2 that changes rapidly across the terminator. In this work we account for diurnal variations in retrievals of NO2 from the SAGE III/ISS measurements, and we determine the impact of this algorithm improvement on the resulting NO2 number densities. The first step in applying the diurnal correction is to use publicly available SAGE III/ISS products to convert the retrieved number density profiles to optical depth profiles. The retrieval is then re-performed with a new matrix that applies photochemical scale factors for each point along the line of sight according to the changing solar zenith angle. In general NO2 that is retrieved by accounting for these diurnal variations is more than 10 % lower than the standard algorithm below 30 km. This effect is greatest in winter at high latitudes and generally greater for sunrise occultations than sunset. Comparisons with coincident profiles from the Optical Spectrograph and InfraRed Imager System (OSIRIS) show that NO2 from SAGE III/ISS is generally biased high; however the agreement improves by up to 20 % in the mid-stratosphere when diurnal variations are accounted for in the retrieval. We conclude that diurnal variations along the SAGE III/ISS line of sight are an important term to consider for NO2 analyses at altitudes below 30 km.

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OH(6-2) spectra and rotational temperature measurements at Davis, Antarctica

Annales Geophysicae ◽

10.1007/s00585-997-0077-3 ◽

1998 ◽

Vol 16 (1) ◽

pp. 77-89 ◽

Cited By ~ 37

Author(s):

P. A. Greet ◽

W. J. R. French ◽

G. B. Burns ◽

P. F. B. Williams ◽

R. P. Lowe ◽

...

Keyword(s):

Middle Atmosphere ◽

Transition Probabilities ◽

Rotational Temperature ◽

Diurnal Variations ◽

Atmospheric Composition ◽

Data Set ◽

Average Temperature ◽

Composition And Structure ◽

Seasonal And Diurnal Variations ◽

Significant Contamination

Abstract. The OH(6-2) band was monitored during 1990 at Davis, Antarctica (68.6°S, 78.0°E) using a Czerny-Turner scanning spectrometer. Spectra obtained with a 0.15-nm bandwidth and wavelength steps of 0.005 nm have been recorded in an attempt to isolate auroral features. This has enabled detailed study of weak features in the region λ837.5–855.5 nm. These weak features can contribute to the apparent intensity of P-branch lines and to the background. Their presence is allowed for in our calculation of rotational temperature, but the P1(3) line is excluded because of significant contamination. An average temperature of 221±2 K is obtained from a selected data set of 104 spectra. The mid-winter average temperature, for the months of May, June and July, is 224±2 K, which is consistent with the 1986 CIRA model values for mid-winter at this height and latitude, but this result is dependent on the choice of transition probabilities. Preliminary assessments of seasonal and diurnal variations in rotational temperature and intensity are presented. Key words. Atmospheric composition and structure · Airglow and aurora; Middle-atmosphere composition and chemistry · Pressure · density and temperature

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