M. García-Comas

SABER observations of mesospheric ozone during NH late winter 2002–2009

[1] Observations from the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument on the TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics) satellite show interannual variations of mesospheric ozone in the NH late winter. Ozone in the mid-January to mid-March period is significantly different in 2004, 2006, and 2009 than in other years (2002, 2003, 2005, 2007, 2008). The altitudes of the ozone secondary maximum (∼90―95 km), the minimum (∼80 km) and the tertiary maximum (∼72 km) are all lower by 3―5 km during the three anomalous winters. The ozone anomalies indicate enhanced downward motion and are consistent with other observations of unusual profiles of trace species. The ozone perturbations extend to at least 100 km while temperatures above 90 km are within the range found in the other years.

Remote sensing of the middle atmosphere with MIPAS

On 1 March 2002 the Envisat research satellite has been launched successfully into its sun-synchronous orbit. One of its instruments for atmospheric composition sounding is the Michelson Interferometer for Passive Atmospheric Sounding, a limb-scanning mid-infrared Fourier transform spectrometer. Different scientific objectives of data users require different approaches to data analysis, which are discussed. A strategy on how to validate the involved algorithms and relevant strategies is presented.

Variability of the Martian thermosphere during eight Martian years as simulated by a ground‐to‐exosphere global circulation model

F.G.G. was partly funded by a CSIC JAE-Doc grant financed by the European Social Fund. F.G.G., M.-A.L.V., and M.G.C. thank the Spanish MICINN for funding support through the CONSOLIDER program ASTROMOLCSD2009-00038 and through projects AYA2011-23552/ESP and AYA2012-39691-C02-01. This work has also been partially funded by the ESA-CNES project Mars Climate Database and Physical Models.

Vibrational‐vibrational and vibrational‐thermal energy transfers of CO2 with N2 from MIPAS high‐resolution limb spectra

We present a retrieval of several vibrational-vibrational (V V) and vibrational-thermal (V-T) collisional rate coefficients affecting the populations of the CO2 levels emitting at 10, 4.3 and 2.7 μm from high-resolution limb atmospheric spectra taken by Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). This instrument has a high spectral resolution (0.0625 cm−1) and a wide spectral coverage (from 685 to 2410 cm−1) that allow measuring and discriminating among the many bands originating the atmospheric 4.3 μm radiance. Also its high sensitivity allows measuring the atmospheric limb emission in a wide altitude range, from 20 to 170 km in its middle and upper atmosphere modes, and hence obtain information on the temperature dependence of the collisional rates. In particular, we retrieve the rate coefficients and their temperature dependence in the 130–250 K range of the following processes: CO2(vd,v3)+N2⇌CO2(vd,v3−1)+N2(1) with vd=2v1+v2=2,3, and 4; CO2(v1,v2,l,1,r)+M⇌CO2(v1′,v2′,l′,1,r′)+M with Δvd=vd′−vd=0 and Δl = 0; and with Δvd=0 and Δl ≠ 0. In addition we have also retrieved the thermal relaxation of CO2(v3) into the v1 and v2 modes, e.g., CO2(vd,v3)+M⇌CO2(vd′,v3−1)+M with Δvd=2–4 and Δv3=−1 and the efficiency of the excitation of N2(1) by O(1D). All of them were retrieved with a much better accuracy than were known before. The new rates have very important effects on the atmospheric limb radiance in the 10, 4.3 and 2.7 μm spectral regions (5–8% at 4.3 μm) and allow a more accurate inversion of the CO2 volume mixing ratio in the mesosphere and lower thermosphere from measurements taken in those spectral regions.

Nighttime ozone variability in the high latitude winter mesosphere

We use satellite observations and a numerical model to investigate polar nighttime ozone at the secondary maximum, around 90–95 km. Observations from the MIPAS and SABER satellite instruments indicate that the highest ozone mixing ratios are seen during the late fall to early winter period in both hemispheres and for all years examined. Simulations using the Whole Atmosphere Community Climate Model (WACCM) find qualitatively the same seasonal evolution. Analysis of WACCM results shows that the high ozone concentration is due in part to the relatively quiet dynamical conditions in early winter. The mean circulation, which brings warmer temperatures and higher concentrations of H, is weaker in early winter than during middle and late winter. H in the late fall to early winter period drops to the lowest levels seen during the year due to lack of a source from photochemistry, weak transport into the region by the mean circulation, and continual loss due to diffusive separation. The low concentration of H leads to higher ozone.

Comparisons of MIPAS-observed temperature profiles with other satellite measurements

MIPAS on ENVISAT measures vertical profiles of atmospheric temperature, ozone, and other species with nearly global coverage and high accuracy/precision. The standard observation mode covers the altitude region between 6 and 68 km. The atmospheric state parameters retrieved from MIPAS measurements using the IMK data analysis processor are compared with a number of other satellite observations. Our comparisons in this paper will focus on temperatures measured by MIPAS, HALOE, SABER, and UKMO Stratospheric Assimilated Data. Both individual profiles and zonal means measured by MIPAS and other instruments at different seasons and geolocations show reasonable agreement, though some differences exist due to characteristics of the individual instruments and observation scenarios. The MIPAS measurements during the stratospheric major sudden warming during the southern hemisphere winter of 2002 are also presented to show the features of this unusual event. The analysis indicates the reliability of MIPAS-IMK data products and their capability for providing valuable scientific information.

The Impact of Energetic Particle Precipitation on the Earths Atmosphere

Energetic particle precipitation (EPP) represents an important Sun–Earth coupling mechanism with important implications on polar stratospheric ozone chemistry. Solar protons generated during solar storms cause sporadically in situ production of stratospheric NO x and HO x radicals involved in catalytic ozone destruction. Further, NO produced continuously in the mesosphere and lower thermosphere by medium energy electron precipitation (EEP) descends to the stratosphere during the polar winter, where it represents an additional, though variable source of NO x . The capability of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) to measure all important NO y species, as well as ClO and HOCl with global coverage including the polar night regions make it an ideal instrument for studying EPP effects on stratospheric chemistry. We present a quantitative assessment of EPP-induced composition changes as observed by MIPAS during 2002–2004, including the unusually strong solar proton event in October/November 2003. The impact of EPP on the stratospheric ozone budget has been studied with chemical models. The stratospheric ozone loss in the polar regions reached 18DU and lasted over months to years.

UV Dayglow Variability on Mars: Simulation With a Global Climate Model and Comparison With SPICAM/MEx Data

A model able to simulate the CO Cameron bands and the CO2+UV doublet, two of the most prominent UV emissions in the Martian dayside, has been incorporated into a Mars Global Climate Model. The model self‐consistently quantifies the effects of atmospheric variability on the simulated dayglow for the first time. Comparison of the modeled peak intensities with Mars Express SPICAM (Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars) observations confirms previous suggestions that electron impact cross sections on CO2 and CO need to be reduced. The peak altitudes are well predicted by the model, except for the period of MY28 characterized by the presence of a global dust storm. Global maps of the simulated emission systems have been produced, showing a seasonal variability of the peak intensities dominated by the eccentricity of the Martian orbit. A significant contribution of the CO electron impact excitation to the Cameron bands is found, with variability linked to that of the CO abundance. This is in disagreement with previous theoretical models, due to the larger CO abundance predicted by our model. In addition, the contribution of this process increases with altitude, indicating that care should be taken when trying to derive temperatures from the scale height of this emission. The analysis of the geographical variability of the predicted intensities reflects the predicted density variability. In particular, a longitudinal variability dominated by a wave‐3 pattern is obtained both in the predicted density and in the predicted peak altitudes.