Separate plots are included for nighttime, twilight and daytime measurements. Spring equinox results are presented which cover parts of the 23rd and 24th solar ...
SABER OH Mesospheric Airglow Emissions
Abstract Mesospheric hydroxyl-airglow volume emission rates were derived from the NASA LaRC/USU SABER instrument aboard the TIMED satellite. The SABER 1.6 μm and 2.0 μm radiometric channels provide measurements of the OH (5,3;4,2) and (9,7;8,6) emission bands, respectively. From these data, the peak values of the volume emission rate and the altitude were ascertained for the OH layer during each valid scan. Global values were interpolated and threedimensional global plots generated using the altitude of the OH (5,3;4,2) peak as the z-axis. The value of the OH (5,3;4,2) volume emission rate at the emission peak is displayed on the three-dimensional surface using a color scale. The ratio of the OH (5,3;4,2) band to the (9,7;8,6) band at the OH (5,3;4,2) altitude of peak emission is also displayed in a similar manner. Separate plots are included for nighttime, twilight and daytime measurements. Spring equinox results are presented which cover parts of the 23rd and 24th solar cycles from 2002 through 2010.
SABER Instrument
Data Processing
Bryant Svedin1 Dr. Doran Baker1 Dr. Gene Ware1 Dr. Martin Mlynczak2 Dr. James Russell3 1Rocky Mountain NASA Space Grant Consortium, 2NASA-Langley Research Center, 3Hampton University
Night OH (5,3;4,2) Peak VER
Ratio at OH (5,3;4,2) Peak
OH (5,3;4,2) Peak VER
Day Ratio at OH (5,3;4,2) Peak
OH (5,3;4,2) Peak VER
Ratio at OH (5,3;4,2) Peak
Fig. 4a – Periods from FFT of Daily Peak VER
2004
2005
2006
2007
background twilight
Volume emission rate values at the peak of each hydroxyl airglow altitude profile were found for the three days surrounding each solstice. Nighttime measurements were designated as having a solar zenith angle greater than 112°, while twilight measurements were between 112° and 68°, and daytime measurements less than 68°. Global emission rates were interpolated from known values using an inpainting technique based on solving a direct system of linear partial differential equations using known values as boundary conditions. The name "inpainting" itself comes from the world of art restoration. Damaged paintings are restored by an artist skilled in matching the style of the original artist to fill in any holes in the painting. Examples of original data and interpolated values are shown in Figs. 3a and 3b.
Twilight
Data was analyzed using Fourier transforms along each latitude taking data from each day at 0° longitude to find latitudinal dependence on changes throughout the year. A strong period of approximately 180 days is observed for the equatorial region. This is consistent with atmospheric tidal effects being greatest around the equator and at the equinoxes.
2002
2003
SABER is a satellite-borne multichannel radiometer used to globally measure infrared emissions from the mesospheric-thermospheric Fig. 1: Overview of the orbit of regions of the Earth’s upper the TIMED satellite and the atmosphere. The NASA SABER instrument. LaRC/USU SABER instrument is onboard the NASA GSFC/JHU TIMED spacecraft launched in December of 2001; it became fully operational in February 2002. Ten different channels measure emissions from eight atmospheric gas species. In order to make its measurements, the SABER sensor observes the emission bands at a tangent point on the horizon using a motion-controlled scanning mirror. This facilitates measurements up to approximately 180 km above the Earth. SABER takes a Fig. 2a - Typical limb scan from scan approximately every 63 the SABER instrument. seconds, providing 1400 to 1500 scans a day. It was found that at twilight irregular OH profiles could result, as shown in Fig. 2b. Inspection motivated the choice of a solar zenith angle greater than that used as the designator in the SABER data set itself to ensure data validity (Fig. 2b). Fig. 2b - Influenced limb scan and
FFT Analysis
2008
2009
Fig. 4b – Periods from FFT of Altitude of Daily Peak VER
Results: Tidal Influences Atmospheric tides have a strong influence on the OH airglow emissions. The increased volume emission rate and lowered peak altitude along the equator can be attributed to the diurnal tide.a Migrating diurnal tides are caused by solar heating of the atmosphere. The tidal amplitude is much larger at equinoxes so the impact is most apparent in March and September.b The results from the FFT analysis in Fig. 4 show that the OH emissions are likely correlated with these tides. The observed effect of lowering the peak altitude and increasing peak volume emission rates along the equator and raised altitudes with lower volume emission rates at ±30° latitude is the result of large scale advection by atmospheric tides. This advection pulls down atomic oxygen near the equator which facilitates increased OH emissions.c,d This is most apparent and easily seen in the 2002 night and day OH emission figures where the result of this advection is an equatorial “trough”. There is insufficient twilight data on the equinoxes to make any determination about tidal effects during this time of day. When looking into atmospheric chemistry, the lifetime of a molecule must be taken into account. If it is short then observations would be based on local photochemistry; if it is long then it can be affected by transport. Atomic oxygen is long-lived (approximately 10 days) and abundant around 90 km.e At night, it reacts with molecular oxygen to form ozone which is then destroyed primarily by reaction with atomic hydrogen through the following process: O + O2 + M → O3 + M; H + O3 → OH* + O2*.
References a Xu,
J., A. K. Smith, G. Jiang, H. Gao, Y. Wei, M. G. Mlynczak, and J. M. Russell III (2010), Strong longitudinal variations in the OH nightglow, Geophys. Res. Lett., 37, L21801, doi:10.1029/2010GL043972. b Xu, J., A. K. Smith, H.‐L. Liu, W. Yuan, Q. Wu, G. Jiang, M. G. Mlynczak, J. M. Russell, and S. J. Franke (2009), Seasonal and quasi‐biennial variations in the migrating diurnal tide observed by Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED), J. Geophys. Res., 114, D13107, doi:10.1029/2008JD011298. c Marsh, D.R., A.K. Smith, M.G. Mlynczak, and J.M. Russell III (2006), SABER observations of the OH Meinel airglow variability near the mesopause, J. Geophys. Res., 111, A10S05, doi:10.1029/2005JA011451. d Shepherd, G. G., C. McLandress, and B. H. Solheim (1995), Tidal influence on O(¹S) Airglow emission rate distributions at the geographic equator as observed by WINDII, Geophys. Res. Lett., 22(3), 275–278, doi:10.1029/94GL03052. e Smith, A. K., M. López-Puertas, M. García-Comas, and S. Tukiainen (2009), SABER observations of mesospheric ozone during NH late winter 2002– 2009, Geophys. Res. Lett., 36, L23804, doi:10.1029/2009GL040942.
Acknowledgements
2010 Fig. 3a Example of original data collected from SABER instrument.
Fig. 3b Interpolated values OH (5,3;4,2) 2002 Spring Equinox
NASA Langley Research Center, Rocky Mountain NASA Space Grant Consortium, Hampton University, USU ECE Dept., USU Physics Dept., GATS, Inc.
http://utahspacegrant.com
