Abstracts from 2007/2008
21/9/07 Matt Toohey: Balloon and space-based measurements of HNO3
Between 1998 and 2004, the MANTRA (Middle Atmosphere TRend Assessment) mission
performed biennial balloon flights from Vanscoy Saskatchewan, making measurements of the chemical
composition of the stratosphere. As the name suggests, part of the mandate of MANTRA was to
investigate potential trends in reactive nitrogen species, which are intimately involved in ozone
chemistry. Two emission radiometer instruments provided a unique opportunity towards this aim: since
they had been flown on similar balloon flights years previously, they provided the opportunity to
perform consistent retrievals of HNO3 on data collected with equivalent instrumentation spanning 12
years. For this week's Brewer seminar, I will (re)introduce the radiometer instruments, the
technique used to retrieve profiles of HNO3, and place these retrievals into the historical record
of HNO3 measurements.
28/9/07 Jeffrey R. Taylor: A Tale of Two Instruments
Once upon a time there was a spectrometer named Fourier. Fourier lived in a
penthouse lab on the 16th floor of a high rise building, known as the Toronto Atmospheric
Observatory. Fourier worked hard, all day long, in the blazing sun, making measurements of chemical
trace gas concentrations. He yearned for a companion with which to spend his time and share his
knowledge of atmospheric composition above Toronto. One day, Fourier met another Canadian
instrument named OSIRIS. OSIRIS was a drifter who travelled all around the world making similar
measurements of chemical gases. The two instruments bonded over their common interest of measuring
ozone (O3) and nitrogen dioxide (NO2) in the stratosphere. Things were going well for years
(2002-2006), until they had a bitter disagreement over the partial columns of NO2 during this time
period. They sought help by using a chemical box model, but it only served to push them apart.
Their last chance is to turn to the new technique of "virtual coincidences". or is it already too
late?! Will Fourier and OSIRIS be able to put their differences aside and learn to live happily
ever after? Is the technique of "virtual coincidences" powerful enough to correct large
disagreements over stratospheric NO2? To learn the answers to all of these questions, come to the
Brewer Seminar on Friday.`
5/10/07 James Anstey: Effects of the QBO on the extratropics in a dynamics-only GCM
The quasi-biennial oscillation (QBO) is a pattern of variability that dominates the
variance of equatorial stratospheric winds but fails to be simulated in most GCMs. By increasing the
vertical resolution in a dynamics-only incarnation of the Canadian Middle Atmosphere Model (CMAM) we
obtain a QBO and consider its effects on the interannual variability of the extratropical middle
atmosphere. As might be expected from observations, some improvement to the warm bias of the CMAM's
northern hemisphere polar vortex occurs when the QBO allows for equatorial westerly zonal winds to
exist in the model's stratosphere (in contrast to the weak tropical easterlies that exist in the
QBO's absence). But this cooling is non-robust due to variability that arises on decadal timescales
in our 150-year model run. We compare this behaviour to that of the real atmosphere, noting that
this version of the CMAM lacks interannually varying sea surface temperatures or external forcings
such as the 11-year solar cycle or trends in chemical consituents.
12/10/07 Petra Huck: Inter- and intra-annual variability in Antarctic ozone depletion
The coupling of dynamics and chemistry in the Antarctic stratosphere is examined to describe inter-
and intra-annual variability in Antarctic ozone depletion. Dynamics in the form of planetary-scale
atmospheric waves can affect the ozone distribution directly through transport of trace gases. In
addition, indirect effects such as heat transport causing temperature changes which in turn modify
ozone destruction have to be considered. Planetary waves can change the dynamical conditions in the
Antarctic stratosphere and thereby change the conditions necessary for ozone destruction. Chemical
ozone depletion depends on the abundance of halogens in the stratosphere, temperature and the
availability of sunlight. In particular, low temperatures (< 195 K) are necessary for the
formation of polar stratospheric clouds which lead to heterogeneous chemistry and chlorine
activation which is a basic requirement for ozone depletion. Based on this theory, statistical
models are developed which can then be used to project inter-annual variability and intra-seasonal
evolution of Antarctic stratospheric ozone depletion into the future.
19/10/07 Constantine Nenkov: A New Model of Thermal Convection: Implications for the Atmospheres of the Gas Giants
In this talk I will give an overview of the newly developed 3D Anelastic GCM on icosahedral grid in
spherical geometry. The idea behind this model is to apply it for the study and modeling of
globally convective planetary atmospheres with large extent, like the atmospheres of Jupiter and
Saturn.
I will start with a broad overview of our current understanding about the physics of the four giant
planets in our Solar system. This is a quickly evolving research field with very important
implications for both Geophysics and Astrophysics. Then I will briefly describe the numerical
technology used in building the model and its most important features. Here I will show how the
model has been tested against established benchmarks, both in the non-rotating and rotating case, as
well as results from critical Rayleigh number searches in a spherically convective fluid shells.
One of the main goals of this research is to attain a better assessment of the qualities and
constraints of this new model of thermal convection, as well as the challenges it faces both from
theoretical and computational point of view. If time permits I will present some results from
long-term integrations of the model which have relevance to zonal flow jet formation in the
atmospheres of Jupiter and Saturn.
26/10/07 Lei Wang: Stationary wave theory, modeling, and applications
The stationary wave, defined as the zonal asymmetries of the atmospheric climatology, is
generated by the zonally varying lower boundary, diabatic heating, and other forcings. Atmospheric
stationary waves are closely related to regional climate, and consequently changes to the stationary
waves resulting from recent global warming might have significant impacts on regional climate
change.
The physical interpretation of the stationary wave is highly complicated due to the nonlinear
interactions between the surface and the atmosphere, but it is still possible to explain the existed
atmospheric zonal asymmetries under a framework in which these complicated processes are neglected.
That is, stationary wave models are able to approach observed atmospheric zonal asymmetries with
much less computational cost than that of GCMs. This talk will illustrate the construction and the
test of a stationary wave model.
2/11/07 Chris Fletcher: Can the Stratosphere Control the Extratropical Circulation Response to Surface Forcing?
Snow extent anomalies over Siberia have been proposed as potential precursors to
stratosphere-troposphere interaction events. However, often these events occur without a clear
tropospheric precursor. We assess the role of snow cover in initiating such events in a 100-member
ensemble of autumn-winter transient integrations using the Geophysical Fluid Dynamics Laboratory
atmosphere/land GCM AM2/LM2. The forcing is a prescribed Siberia region snow mass perturbation,
which does indeed induce a stratosphere-troposphere interaction response. On seasonal timescales we
demonstrate that the coupling of the stratospheric response to the surface depends on the state of
the stratosphere prior to the initiation of the forcing. An initially weak stratospheric polar
vortex increases the likelihood of a negative Northern Annular Mode response at the surface. This
result could have practical implications for the general problem of the prediction of circulation
anomalies arising from surface forcing in the extratropics.
9/11/07 Peter Hitchcock: Are the Coldest Winters in the Arctic Stratosphere Getting Colder?
Temperatures low enough for the formation of Polar Stratospheric Clouds (PSCs) have
become increasingly widespread in the Arctic stratosphere over the past four decades, despite the
lack of an apparent cooling trend in the mean temperatures. Since PSCs are strongly implicated in
the chemical destruction of ozone, this trend could have troubling consequences. It has been argued
that this is a sign of climate change, though details of the mechanism remain unclear. This Friday I
will discuss polar stratospheric temperatures in an ensemble of three, 150-year integrations of the
Canadian Middle Atmosphere Model (CMAM) which include representations of ozone depletion/recovery
and climate change. While the distinct radiative effects of ozone depletion and carbon dioxide
increase are clearly seen in the Antarctic temperature extremes, any such effects in the northern
hemisphere of the model are overwhelmed by the strong variability of the Arctic vortex.
16/11/07 Robert Field: Identifying controls on stable water isotope composition with a GCM
In this talk, I will report on our efforts to better understand controls on
the stable water isotope composition of precipitation. Since their
development in the 1980's, GCMs equipped with stable water isotope
diagnostics have been used to identify climatological controls on
precipitation δ18O. These studies have been important in identifying
controls on δ18O in data-poor regions, and in the absence of complicating
factors such as post-depositional effects on snowfall. They are, however,
similar to observational studies, in that isotopic variability is not being
attributed to a particular control in a strict physical sense because of
possible collinearity between explanatory variables.
As an alternative, we are conducting a series of sensitivity experiments
using the GISS ModelE GCM, whereby different fractionation processes are
systematically disabled to determine the dominant controls of δ18O. Our
results show that variability in precipitation δ18O is controlled almost
exclusively by atmospheric processes. Surface processes make a negligible
contribution, except perhaps in regions adjacent to heavy vegetation where
moisture recycling could play an important role.
23/11/07 Jane Liu: Revisiting "the Tropospheric Middle East Ozone Maximum" with Satellite Observations of Tropospheric Ozone
Previous modelling and observational studies suggest the existence of a seasonal
buildup in tropospheric ozone over the Middle East, which is so called the "Middle East Ozone
Maximums" (Li et al. 2001 and Kar et al. 2002, Geophyiscal Research Letters). However, more
evidences are needed to confirm or reject this suggestion because of its high uncertainty. In this
study, we revisited this issue using a chemical transport model, GEOS-CHEM, the newly available
tropospheric ozone data from the Tropospheric Emission Spectrometer (TES) satellite, and in-situ
ozone sonde data. We found that there is a summer-time ozone enhancement in a narrow layer of
altitudes around 400 hPa in the in-situ data. This enhancement disappears in the other seasons. The
seasonal variation of the ozone vertical profile in the in-situ data can be mostly captured by both
TES and GEOS-CHEM. Spatially, the "Middle East ozone maximum" is visible in the TES images, with
some inter-annual variations in its extent.
The seasonal cycle of ozone over the Middle East region was examined by isolating the influence of
photochemical production and transport on the ozone budget in the region. A tagged ozone simulation
was conducted to track ozone in the region from its origins in Asia, Africa, North America, and
European. The results suggest that although long-range transport and in situ chemical production
both contribute to the formation of the ozone enhancement, transport appears to be the major source.
The majority of transported ozone comes from Asia in the mid-upper troposphere and from African in
the middle troposphere. The accumulation of ozone in the region is strongly related to the location
and movement of the Arabian anticyclone. The TES data show enhanced ozone extending from North
Africa to Central Asia, over a larger area than what GEOS-CHEM predicted, reflecting possible biases
in the model transport over these regions.
30/11/07 Tiffany A. Shaw: Wave-activity conservation laws and their application to subgrid-scale parameterization in climate models
It is common in fluid dynamical applications to consider the fluid state as a
disturbance to some specified background reference state. In such cases wave-activity conservation
laws play a central role and their most general formulation follows from Hamiltonian geophysical
fluid dynamics. In the case of the large-scale circulation of the middle atmosphere the
Eliassen-Palm wave activity has been crucial to theoretical analysis. In the case of the mesoscale,
whose interaction with the large scales is represented in climate models through subgrid-scale
parameterizations, one generally considers three-dimensional disturbances to a horizontally
homogeneous but vertically dependent background flow. While such conservation laws have been applied
to a horizontally homogeneous background flow in two-dimensions their application to the
three-dimensional problem fails because of a degeneracy created by the absence of a potential
vorticity gradient. Here we will show how this degeneracy can be overcome and wave-activity
conservation laws derived for three-dimensional disturbances to a horizontally homogeneous
background flow. The role of the wave-activity fluxes in forcing the large-scale energy and momentum
budgets will be briefly discussed and their usefulness in constraining the fluxes of parameterized
energy and momentum will also be highlighted.
7/12/07 Yonggang Liu: A Carbon-Cycle Coupled Climate Model: Implications for the "Snowball Earth" hypothesis
The profound negative carbon isotopic excursions and the glaciogenic deposits
associated with them found within the ancient Neoproterozoic interval of time (1000 Ma - 545 Ma)
have stimulated both speculation and debate concerning the spatial extent of the glaciations, the
extremity of the accompanying climate and the consequences for biological evolution. Some
researchers believe that only a series of "hard snowball Earth" events (in which ice covered all of
the continents as well as the entire surface of the oceans) can explain the observed sedimentary
records. Here I will argue that the alternative "slushball Earth" scenario (in which the equatorial
oceans are never entirely ice covered) combined with a special carbon cycle model appropriate for
the Neoproterozoic is able to explain the available isotopic data. The results of coupled model
integrations demonstrate that the interaction of the physical climate system with the carbon cycle
may support a cyclic mode of glaciation, the timscale of which is carbon cycle controlled. The model
has been proved to be able to excellently explains the younger glaciation event (Marinoan
glaciation, ~650 Ma), but for the older one (Sturtian glaciation, ~720 Ma), in which the continents
are claimed to be mostly distributed in the low-latitude region, this simple model cannot produce a
similar cyclic glaciation. Either more complex mechanism needs to be invoked in the model, or causes
other than carbon cycle (e.g., true polar wander) should be found to explain the Sturtian
glaciation.
14/12/07 Carling Hay: Case Study of a Greenland Tip Jet
Standing over 3000m tall in some regions, Greenland's southern tip acts as a large
barrier to storm systems traversing the North Atlantic. As a result of the interaction with
Greenland, low-pressure systems located in the Irminger Sea between Iceland and Greenland often
produce strong low-level winds. These westerly low-level winds are known as tip jets and can have
magnitudes in excess of 30 m/s. On November 29th 2004 a lee cyclone in the Irminger Sea produced a
tip jet event that was captured by a meteorological buoy positioned off the southwest tip of
Greenland. The Weather Research and Forecasting Model (WRF) along with an air parcel trajectory
analysis has been used to study the system that produced the tip jet as well as the characteristics
of the winds themselves.
11/01/08 Annemarie Fraser: UV-visible measurements of Ozone and NO2 during the Canadian Arctic ACE Validation Campaigns: 2004-2007
The first four Canadian Arctic ACE validation campaigns were held during polar
sunrise at Eureka, Nunavut from 2004 to 2007 in support of validation of the ACE (Atmospheric
Chemistry Experiment) satellite mission. Three to five zenith-sky viewing UV-visible spectrometers
have taken part in each of the four campaigns.
During my Brewer I'll introduce you to the five UV-visible spectrometers that have taken part in the
ACE campaigns, and discuss how their measurements of ozone and NO2 compare. I'll also compare the
total columns from the ground-based instruments to integrated total columns from ozonesondes and
integrated partial columns from the two instruments on board ACE: ACE-FTS (ACE-Fourier Transform
Spectrometer) and ACE-MAESTRO (ACE-Measurements of Aerosol Extinction in the Stratosphere and
Troposphere Retrieved by Occultation).
As an added bonus, I'll show you what the newest instrument, the PEARL-GBS (Polar Environment
Atmospheric Research Lab - Ground Based Spectrometer), has been doing since it was permanently
installed in Eureka in August 2006.
18/01/08 Peifeng Yan: The infrared absorption cross-sections of CFC-113
CFC-113 is the third most abundant chlorofluorocarbon in the atmosphere.
Its impact on ozone depletion and global warming require accurate
measurement of its concentration. Currently, the lack of cross-section
measurements is the major limitation for the retrieval of this species
from atmospheric spectra. In this work, a CFC-113 spectrum recorded in
2005 at room temperature (294 K) was analyzed to derive a cross-section
and was compared with existing data. The temperature-dependence of the
peak cross-sections and the temperature-independence of the integrated
band strengths were also studied. A thermocouple performance test was
performed with carbon monoxide as preparatory work for future CFC-113
temperature measurements. A multi-pass White cell is being commissioned to
enable measurements of weak absorption cross-sections features of CFC-113,
and measurements of some infrared line parameters of a number of
greenhouse gases and atmospheric constituents. These data will be
invaluable for retrieval and remote sounding of atmospheric constituents.
25/01/08 Jing Wang: Retrieval of Sulfur Dioxide from GOME Instrument Using Optimal Estimation Inversion Technique
Sulfur dioxide (SO2) is an important trace gas, both under background
conditions and in polluted areas. The purpose of using the previous GOME
measurement is to get better monthly retrievals of SO2 and then improve
our understanding of the trend of SO2 emission in recent decade. In the
talk, I'll present the short timescale retrievals of SO2 from the
measurements of Global Ozone Monitoring Experiment (GOME) in UV spectral
region for both volcanic and anthropogenic emissions using Optimal
Estimation (OE) inverse technique. The results will be compared with the
retrieval using Nonlinear Least Squares Fitting method, showing the
advantage of OE in both emission sources. And our work has improved the
previous retrieval using OE in anthropogenic emission by applying better
fitting window, which is validated by the measurements from CASTNET (Clean
Air Status and Trends Network) in the United States.
08/02/08 Rebekah Martin: A tale of two tip jets: Case studies of two Greenland tip jets
Since its discovery 10 years ago, the Greenland tip jet has been a focus of study as an
orographically induced phenomenon that supports intense air sea interaction. Much of the research
on this weather system has been to characterize its structure and the environmental conditions that
give rise to it. As a result, its genesis mechanism has not been addressed in depth. We present
here the results of mesoscale simulations of two Greenland tip jet events, and discuss some of the
factors that were important to their development that should be included in a theory of tip jet
formation. Both of these events were classified as strong events based on climatologies developed
from reanalysis and satellite data, however their genesis was significantly different, and these
cases could be considered as two end members of the spectrum of tip jet events. The first case took
place from 17-19 February, 1997, and was one of the cases addressed in the first work on tip jets,
while the second occurred over 22-24 January, 2001. Although these cases occurred under slightly
different synoptic forcing conditions and had different mature configurations, they highlight
similarities between tip jet events that could be extrapolated to occur for most events.
Time permitting I will also review a case study of a reverse tip jet event that occurred in
December 2001 for the purposes of even more fun and frivolity.
15/02/08 Rodica Lindenmaier: Studies of Arctic Middle Atmosphere Chemistry Using Infrared Absorption Spectroscopy: Optimization of Ozone Retrievals
A new high-resolution Infrared Fourier Transform Spectrometer (FTS) was installed at
the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut in
July 2006.
The new instrument is being used to measure solar absorption spectra in the mid-infrared from which
total columns and some vertical profile information can be retrieved for a suite of trace gases that
are involved in the process of stratospheric ozone depletion.
It is well known that, after the long polar winter which creates special conditions for reactive
chlorine and bromine radicals to develop, the process of rapid ozone loss begins. This is well
understood now in Antarctica where the springtime ozone hole is fairly stable from year to year.
Arctic winter/spring total ozone columns show large interannual variability due to large variations
from year to year in the area of the Arctic vortex, the strength of the sudden warmings, and the
timing of the final vortex breakdown all of which can affect the amount of chemical ozone loss.
Long-term observations are essential to address the question of “What is the composition of the
Arctic atmosphere above the site and how is it changing with time?” In my research activity I would
like to improve our understanding of the processes controlling the Arctic stratospheric ozone budget
and its future evolution, using measurements of the concentrations of stratospheric constituents.
This talk will present measurements recorded with the new instrument during its first year of
operation, including those from the Canadian Arctic ACE Validation spring campaign in 2007.
Particular consideration will be given to optimizing the ozone retrievals. The performance of the
instrument will be discussed, along with details of the retrieval process, trace gas measurements,
and future plans.
29/02/08 Dmitry Vyushin: Power-law and long-memory characteristics of the atmospheric general circulation
The question of which statistical model best describes internal climate
variability on interannual and longer timescales is key to our ability
to predict such variables and detect periodicities and trends in them.
For over 30 years the dominant model for background climate variability
has been the autoregressive model of the first order (AR1). But recent
research has shown that some aspects of climate variability are best
described by a "long-memory" or "power-law" model. Such a model fits a
temporal spectrum to a single power-law function which thereby
accumulates more power at lower frequencies than an AR1 fit. In this
study, several power-law model estimators are applied to global
temperature data from reanalysis products. The methods employed
(detrended fluctuation analysis, Geweke Porter-Hudak estimator, Gaussian
semiparametric estimator, and multitapered versions of the last two)
agree well for pure power-law stochastic processes. But for the
observed temperature record, the power-law fits are sensitive to the
choice of frequency range and the intrinsic filtering properties of the
methods. The observational results converge once frequency ranges are
made consistent and several climate signals have been filtered. Two
robust results emerge from the analysis: first, that the tropical
circulation features relatively large power-law exponents that connect
to the zonal-mean extratropical circulation; and second, that the
subtropical lower stratosphere exhibits power-law behaviour that is
volcanically forced.
7/03/08 Dave MacKenzie: Transport of CO and O3 into the UTLS Region
Changes in O3 in the upper troposphere and lower stratosphere
(UTLS) can influence the climate system. We examine the influence of
tropospheric pollution on O3 in the UTLS. The GEOS-Chem global chemical
transport model is used to quantify the transport of pollution to the UTLS
from different source regions in the troposphere. To assess cross
tropopause transport we focus on the correlations between CO and O3. These
results are compared with output from the GMI Combo model and SPURT
aircraft data to help describe UTLS mixing.
14/03/08 Zhe Jiang: Quantifying the impact of aggregation errors and model transport biases on top-down estimates of carbon monoxide emissions using satellite’s observations
We conducted an inverse analysis of atmospheric CO, using the GEOS-Chem model and
observations from the MOPITT satellite instrument, to quantify the potential contribution of model
transport error and aggregation errors to top-down source estimates. We focus on quantifying CO
emissions for September 2000, during the biomass burning season. Using a 4-dimensional variational
data assimilation scheme, we optimize the CO emissions on the 2°x2.5° grid of the model. The
high-resolution, a posteriori source estimates are compared with estimates obtained from a coarse
resolution, analytical Bayesian inversion to quantify the impact of aggregation errors in the coarse
resolution inversion on the source estimates. We also carry out the coarse resolution analytical
inversion using two different versions of the GEOS-Chem model, driven with different transport
fields, to isolate the impact on the source estimates of systematic differences in transport in the
models.
4/04/08 Thomas Walker: Tropospheric Ozone at High Latitudes: An Initial Look
Despite a paucity of pollution sources, the Arctic atmosphere experiences
ozone accumulation, which affects the surface air quality and the local
radiation budget. We use a global chemical transport model (GEOS-Chem) to
study the seasonal cycles in PAN and ozone at high latitude sites, both on
the ground and aloft, and compare to in situ datasets where available. We
observe an early springtime maximum in both PAN and ozone at the surface.
Aloft, we observe a shift in the timing of stratospheric downwelling
between the model and observation. A tagged ozone simulation reveals four
continental source regions of interest for transport to high latitudes as
well as the temporal and spatial distributions of ozone originating in
these regions.
11/04/08 Karen Smith: The transient response to localized surface cooling in a simple AGCM
Terrestrial snow cover constitutes the largest areal component of the
cryosphere and experiences the largest spatial and temporal
fluctuations of Earth's surface conditions. Consequently, it exerts a
strong influence over global climate. In addition to the role of snow
cover in the surface energy and moisture budgets, recent studies have
shown that the circulation response to the diabatic forcing associated
with seasonal snow cover anomalies projects onto the leading mode of
extratropical variability, the Northern Annular Mode (NAM). Therefore,
snow variability can potentially induce large-scale changes in the
circulation. Using an idealized dry, hydrostatic, primitive equation
model, the transient response to surface cooling is investigated. We
find that responses generated by our simple model differ from snow
forcing studies in comprehensive GCMs. The ability of our simple model
to capture sudden warming dynamics and stratosphere-troposphere
coupled variability is likely an important factor in interpreting our
cooling experiments.
18/04/08 Cristen Adams: UV-visible measurements from the 2008 field campaign at Eureka, Nunavut: Preliminary results and future plans
This spring, I took measurements with two spectrometers at the Polar Environment
Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80N, 86W). The UT-GBS
(University of Toronto Ground-Based Spectrometer) and the PEARL-GBS (PEARL Ground-Based
Spectrometer) are nearly identical spectrometers that measure in the UV-visible region. During the
spring 2008 campaign, both instruments recorded some zenith-sky measurements of scattered sunlight,
which yield vertical columns with primarily stratospheric information. I will discuss some
preliminary vertical column measurements of ozone and NO2, as well as current progress toward
retrieving BrO vertical columns. This spring, we installed a sun-tracker above the PEARL-GBS, with
the goal of detecting "bromine explosions", sudden increases in tropospheric bromine in the
springtime that are thought to originate from newly forming sea-ice. I will describe the
measurements that we are taking for this purpose, and future plans to combine the direct-sun
measurements (for tropospheric sensitivity), with the zenith-sky measurements (for stratospheric
sensitivity) in order to measure tropospheric and stratospheric partial columns of BrO above Eureka.
2/05/08 Marie-Ève Gagné: Using airglow to derive temperature and density profileson Mars
Middle-atmospheric (50 - 100 km) temperature measurements of Mars are rare and
unreliable because of the high opacity of the atmosphere. The absorption bands of the standard
sensors used to infer temperature quantities, i.e. in the thermal infrared region, are mostly
saturated due to the high concentration of carbon dioxide (CO2) in the Martian atmosphere, as the
main absorption lines of CO2 cover most of this spectral region. Airglow measurements provide a
highly promising approach for the determination of temperature and atomic-oxygen density over this
altitude range given the strong heritage of this technique for Earth observations. Airglow has been
observed during the Mariner 6, 7 & 9 missions to Mars; the presence of atmospheric airglow features
in different spectral regions has recently been confirmed by the measurements of SPICAM on board
Mars EXpress.
The presentation will review the measurements of middle-atmospheric temperatures and airglow on
Mars. The airglow features of the Herzberg I, II & III and Chamberlain bands of the O2 transitions
will be explained. Finally, the first simulations of the Martian airglow from those emission bands
will be presented. The simulations use profiles from a time-dependent photochemical model that solves for the diurnal changes in composition driven by varying insolation between the ground and 100 km altitude.
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