Maya García-Comas

Bio: Maya García-Comas is an academic researcher from Spanish National Research Council. The author has contributed to research in topics: Thermosphere & Mesosphere. The author has an hindex of 25, co-authored 71 publications receiving 1830 citations. Previous affiliations of Maya García-Comas include Max Planck Society & University of Granada.

Assessment of the quality of the Version 1.07 temperature‐versus‐pressure profiles of the middle atmosphere from TIMED/SABER

Abstract: The quality of the retrieved temperature-versus-pressure (or T(p)) profiles is described for the middle atmosphere for the publicly available Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) Version 1.07 (V1.07) data set. The primary sources of systematic error for the SABER results below about 70 km are (1) errors in the measured radiances, (2) biases in the forward model, and (3) uncertainties in the corrections for ozone and in the determination of the reference pressure for the retrieved profiles. Comparisons with other correlative data sets indicate that SABER T(p) is too high by 1-3 K in the lower stratosphere but then too low by 1 K near the stratopause and by 2 K in the middle mesosphere. There is little difference between the local thermodynamic equilibrium (LTE) algorithm results below about 70 km from V1.07 and V1.06, but there are substantial improvements/differences for the non-LTE results of V1.07 for the upper mesosphere and lower thermosphere (UMLT) region. In particular, the V1.07 algorithm uses monthly, diurnally averaged CO2 profiles versus latitude from the Whole Atmosphere Community Climate Model. This change has improved the consistency of the character of the tides in its kinetic temperature (T(sub k)). The T(sub k) profiles agree with UMLT values obtained from ground-based measurements of column-averaged OH and O2 emissions and of the Na lidar returns, at least within their mutual uncertainties. SABER T(sub k) values obtained near the mesopause with its daytime algorithm also agree well with the falling sphere climatology at high northern latitudes in summer. It is concluded that the SABER data set can be the basis for improved, diurnal-to-interannual-scale temperatures for the middle atmosphere and especially for its UMLT region.

Errors in Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) Kinetic Temperature Caused by Non-Local Thermodynamic Equilibrium Model Parameters

Abstract: The vast set of near global and continuous atmospheric measurements made by the SABER instrument since 2002, including daytime and nighttime kinetic temperature (T(sub k)) from 20 to 105 km, is available to the scientific community The temperature is retrieved from SABER measurements of the atmospheric 15 micron CO2 limb emission This emission separates from local thermodynamic equilibrium (LTE) conditions in the rarefied mesosphere and thermosphere, making it necessary to consider the CO2 vibrational state non-LTE populations in the retrieval algorithm above 70 km Those populations depend on kinetic parameters describing the rate at which energy exchange between atmospheric molecules take place, but some of these collisional rates are not well known We consider current uncertainties in the rates of quenching of CO2 (v2 ) by N2 , O2 and O, and the CO2 (v2 ) vibrational-vibrational exchange to estimate their impact on SABER T(sub k) for different atmospheric conditions The T(sub k) is more sensitive to the uncertainty in the latter two and their effects depend on altitude The T(sub k) combined systematic error due to non-LTE kinetic parameters does not exceed +/- 15 K below 95 km and +/- 4-5 K at 100 km for most latitudes and seasons (except for polar summer) if the Tk profile does not have pronounced vertical structure The error is +/- 3 K at 80 km, +/- 6 K at 84 km and +/- 18 K at 100 km under the less favourable polar summer conditions For strong temperature inversion layers, the errors reach +/- 3 K at 82 km and +/- 8 K at 90 km This particularly affects tide amplitude estimates, with errors of up to +/- 3 K

Large abundances of polycyclic aromatic hydrocarbons in titan's upper atmosphere

Abstract: In this paper, we analyze the strong unidentified emission near 3.28 μm in Titan's upper daytime atmosphere recently discovered by Dinelli et al. We have studied it by using the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 μm. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) × 104 particles cm–3. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is ~430 u; the mean area is about 0.53 nm2; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.

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

Abstract: 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.

Evidence for dynamical coupling from the lower atmosphere to the thermosphere during a major stratospheric warming

Abstract: [1] We used temperature data from the Michelson Interferometer for Passive Atmospheric Sounding on board ESA's Envisat satellite to analyze the temperature responses in the mesosphere and thermosphere up to 170 km to a major stratospheric sudden warming (SSW) which occurred in January 2009. The temperature observations show clear signatures of a mesospheric cooling and a thermospheric warming, the latter peaking at 120–140 km in agreement with model predictions. From the analysis of the zonal temperature structure during the SSW a pronounced wave 1 pattern was found in the entire middle and upper polar atmosphere with maximum amplitudes around 50 and 140 km. In the mesosphere, the wave amplitude is significantly damped. The wave amplification above is most likely produced by in situ forced planetary waves in the mesosphere and lower thermosphere region. Our observations represent the first experimental evidence of a dynamical coupling of the lower atmosphere and the thermosphere in the 120–150 km range by means of satellite data.

Climate Change from 1850 to 2005 Simulated in CESM1(WACCM)

Abstract: The NCAR Community Earth System Model (CESM) now includes an atmospheric component that extends in altitude to the lower thermosphere. This atmospheric model, known as the Whole Atmosphere Community Climate Model (WACCM), includes fully interactive chemistry, allowing, for example, a self-consistent representationofthedevelopmentandrecoveryofthestratosphericozoneholeanditseffectonthetroposphere.This paper focuses on analysis of an ensemble of transient simulations using CESM1(WACCM), covering the period from the preindustrial era to present day, conducted as part of phase 5 of the Coupled Model Intercomparison Project. Variability in the stratosphere, such as that associated with stratospheric sudden warmings and the development of the ozone hole, is in good agreement with observations. The signals of these phenomena propagate into the troposphere, influencing near-surface winds, precipitation rates, and the extent of sea ice. In comparison of tropospheric climate change predictions with those from a version of CESM that does not fully resolve the stratosphere, the global-mean temperature trends are indistinguishable. However, systematic differences do exist in other climate variables, particularly in the extratropics. The magnitude of the difference can be as large as the climate change response itself. This indicates that the representation of stratosphere‐ troposphere coupling could be a major source of uncertainty in climate change projections in CESM.

MIPAS: an instrument for atmospheric and climate research

Abstract: MIPAS, the Michelson Interferometer for Pas- sive Atmospheric Sounding, is a mid-infrared emission spectrometer which is part of the core payload of ENVISAT. It is a limb sounder, i.e. it scans across the horizon detecting atmospheric spectral radiances which are inverted to verti- cal temperature, trace species and cloud distributions. These data can be used for scientific investigations in various re- search fields including dynamics and chemistry in the alti- tude region between upper troposphere and lower thermo- sphere. The instrument is a well calibrated and characterized Fourier transform spectrometer which is able to detect many trace constituents simultaneously. The different concepts of retrieval methods are described including multi-target and two-dimensional retrievals. Operationally generated data sets consist of temperature, H2O, O3, CH4, N2O, HNO3, and NO2 profiles. Measurement errors are investigated in de- tail and random and systematic errors are specified. The re- sults are validated by independent instrumentation which has been operated at ground stations or aboard balloon gondolas and aircraft. Intercomparisons of MIPAS measurements with other satellite data have been carried out, too. As a result, it

The Atmospheric Chemistry Experiment (ACE): Mission Overview

Abstract: ACE is a Canadian satellite mission that will provide measurements leading to an improved understanding of the chemical and dynamical processes that control the distribution of ozone in the stratosphere. The ACE instruments are a Fourier transform infrared spectrometer, a UV/visible/near IR spectrograph and a two-channel solar imager, all working in solar occultation mode. ACE was successfully launched on August 12, 2003.

The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere

Abstract: . The new Modular Earth Submodel System (MESSy) describes atmospheric chemistry and meteorological processes in a modular framework, following strict coding standards. It has been coupled to the ECHAM5 general circulation model, which has been slightly modified for this purpose. A 90-layer model setup up to 0.01 hPa was used at spectral T42 resolution to simulate the lower and middle atmosphere. With the high vertical resolution the model simulates the Quasi-Biennial Oscillation. The model meteorology has been tested to check the influence of the changes to ECHAM5 and the radiation interactions with the new representation of atmospheric composition. In the simulations presented here a Newtonian relaxation technique was applied in the tropospheric part of the domain to weakly nudge the model towards the analysed meteorology during the period 1998–2005. This allows an efficient and direct evaluation with satellite and in-situ data. It is shown that the tropospheric wave forcing of the stratosphere in the model suffices to reproduce major stratospheric warming events leading e.g. to the vortex split over Antarctica in 2002. Characteristic features such as dehydration and denitrification caused by the sedimentation of polar stratospheric cloud particles and ozone depletion during winter and spring are simulated well, although ozone loss in the lower polar stratosphere is slightly underestimated. The model realistically simulates stratosphere-troposphere exchange processes as indicated by comparisons with satellite and in situ measurements. The evaluation of tropospheric chemistry presented here focuses on the distributions of ozone, hydroxyl radicals, carbon monoxide and reactive nitrogen compounds. In spite of minor shortcomings, mostly related to the relatively coarse T42 resolution and the neglect of inter-annual changes in biomass burning emissions, the main characteristics of the trace gas distributions are generally reproduced well. The MESSy submodels and the ECHAM5/MESSy1 model output are available through the internet on request.