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Author Lopez-Valverde, M. A. ♦ Montabone, L. ♦ Sornig, M. ♦ Sonnabend, G.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword ASTROPHYSICS, COSMOLOGY AND ASTRONOMY ♦ CARBON DIOXIDE ♦ COMPARATIVE EVALUATIONS ♦ DOPPLER EFFECT ♦ EMISSION ♦ ILLUMINANCE ♦ JETS ♦ LTE ♦ MARS PLANET ♦ PLANETARY ATMOSPHERES ♦ RADIANT HEAT TRANSFER ♦ SATELLITE ATMOSPHERES ♦ SOLAR WIND ♦ VENUS PLANET
Abstract A detailed analysis is presented of ground-based observations of atmospheric emissions on Mars and Venus under non-local thermodynamic equilibrium (non-LTE) conditions at high spectral resolution. Our first goal is to comprehend the difficulties behind the derivation of wind speeds from ground-based observations. A second goal is to set a framework to permit comparisons with other observations and with atmospheric models. A forward model including non-LTE radiative transfer is used to evaluate the information content within the telescopic beam, and is later convolved with the beam function and a typical wind field to discern the major contributions to the measured radiance, including limb and nadir views. The emission mostly arises from the non-LTE limb around altitudes of 75 km on Mars and 110 km on Venus. We propose a parameterization of the limb emission using few geophysical parameters which can be extended to other hypothetical CO{sub 2} planetary atmospheres. The tropospheric or LTE component of the emission varies with the temperature and is important at low solar illumination but only for the emerging radiance, not for the wind determinations since these are derived from the Doppler shift at the non-LTE line cores. We evaluated the sources of uncertainty and found that the forward model errors amount to approximately 12% of the measured winds, which is normally smaller than the instrumental errors. We applied this study to revise a set of measurements extending for three Martian years and confirmed previous results suggesting winds that are too large simulated by current Martian circulation models at equatorial latitudes during solstice. We encourage new observational campaigns, particularly for the strong jet at mid–high latitudes on Mars, and propose general guidelines and recommendations for future observations.
ISSN 0004637X
Educational Use Research
Learning Resource Type Article
Publisher Date 2016-01-10
Publisher Place United States
Journal Astrophysical Journal
Volume Number 816
Issue Number 2


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