Water Vapor Saturation at Low Altitudes around Mars Aphelion: A Key to Mars Climate?

Clancy, R. T.; Grossman, A. W.; Wolff, Michael; James, P. B.; Rudy, D. J.; Billawala, Youssef; Sandor, Brad J.; Lee, S.W.; Muhleman, D. O.

doi:10.1006/icar.1996.0108

Cited by 327 publications

(289 citation statements)

References 17 publications

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“…At tropical latitudes, the variation in height of the phasing of the temperature maximum will affect the diurnal cycle of cloud growth and decay. For example, a tendency for tropical clouds to dissipate in late morning (Colburn et al 1989) might suggest that they are forming at relatively low altitudes, which would be consistent with the lower temperatures implied by our revision of IRTM temperatures, and with the results of Clancy et al (1996). Figure 16a indicates that a transition from maximum temperatures at midday to morning hours may occur at at ∼1-2 mb (∼15 km).…”

Section: Water-ice Cloudssupporting

confidence: 82%

“…The potential significance of a lower saturation level has been discussed by Clancy et al (1996) in the context of the relatively cooler microwave temperatures. Hubble Space Telescope images , the analysis of IRTM T 11 and T 20 data (Tamppari et al 2000, Toigo andRichardson 2000), and the analysis of MGS TES spectra (Pearl et al 1999) have suggested that an extensive tropical water ice cloud belt may be a prominent feature of the martian atmosphere during the aphelion season.…”

Section: Water-ice Cloudsmentioning

confidence: 99%

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The Martian Atmosphere During the Viking Mission, I Infrared Measurements of Atmospheric Temperatures Revisited

Wilson¹

2000

Icarus

112

135

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The Viking Infrared Thermal Mapper 15-µm channel brightness temperature observations (IRTM T 15 ) provide extensive spatial and temporal coverage of martian atmospheric temperatures on diurnal to seasonal time scales. The 15-µm channel was designed so that these temperatures would be representative of a deep layer of atmosphere centered at 0.5 mb (∼25 km). Our re-examination of the IRTM data indicates that the 15-µm channel was additionally sensitive to surface radiance so that air temperature determinations (nominal T 15 ) are significantly biased when the thermal contrast between the surface and atmosphere is large. This bias is suggested by the strong correlation between the diurnal variation of tropical T 15 and surface temperatures for non-dust-storm conditions. We show that numerical modeling of the thermal tides provides a basis for distinguishing between the surface and atmospheric contributions to IRTM T 15 and thus allows the atmospheric component to be estimated. The resulting bias amounts to a ∼15-K offset for midday atmospheric temperatures at subsolar latitudes during relatively clear periods and is negligible at night. The proposed temperature correction results in close agreement between the stimulated and observed patterns of diurnal variation for conditions ranging from clear to dusty.A major consequence of this work is the improved definition of the diurnal, latitudinal, and seasonal variation of martian atmosphere temperatures during the Viking mission. An accounting for the surface temperature bias resolves much of the discrepancy between IRTM and corresponding microwave observations, indicating that there is relatively little interannual variability in global temperatures during the aphelion season (L s ∼ 40• -100 • ). We find further support for this argument in a comparison with T 15 temperatures synthesized from Mariner 9 Infrared Interferometer Spectrometer spectra. The significantly reduced diurnal temperature variations in this season are consistent with the relatively clear atmosphere that is implied by the cooler temperatures. Cooler temperatures and reduced diurnal variation will likely be of significance for the modeling of water ice cloud dynamics in this season.

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Section: Water-ice Cloudssupporting

confidence: 82%

Section: Water-ice Cloudsmentioning

confidence: 99%

The Martian Atmosphere During the Viking Mission, I Infrared Measurements of Atmospheric Temperatures Revisited

Wilson¹

2000

Icarus

112

135

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“…When folded with the PHIFE, which also depends on the solar zenith angle, it results in a compli.cated picture of the production of HD from HDO. The particular atmospheric profile that was taken in this study holds for Mars aphelion conditions during northern late spring/early summer at low latitude [Clancy et al, 1996]. According to these authors, it is when the hygropause is at its lowest altitude (at midlatitude).…”

Section: Effectmentioning

confidence: 99%

Isotopic fractionation through water vapor condensation: The Deuteropause, a cold trap for deuterium in the atmosphere of Mars

Bertaux¹,

Montmessin²

2001

J. Geophys. Res.

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“…Both Viking landers obtained records of atmospheric pressure, temperature, and wind velocity at the surface that extended over several Mars years. More recent Earth-based, disk-averaged microwave observations have been interpreted to indicate episodic cooling of the martian lower atmosphere by about 20 K relative to the conditions observed during the Viking missions (4). By continuing the Viking record after 21 years, ASI/MET results are able to determine whether martian meteorology and climate have changed or remained stable in the late northern summer.…”

mentioning

confidence: 99%

“…In view of the similar solar forcing, it is not surprising that the Pathfinder and VL-1 profiles are comparable in the lower atmosphere. However, Earth-based, disk-averaged microwave observations over the past 10 to 15 years have been used to suggest that the martian lower atmosphere undergoes episodes of cooling, which are characterized by reduced solar-absorbing dust content and 20 K lower temperatures relative to the conditions observed during the Viking mission (4). The Pathfinder entry profile shows no evidence for substantial cooling of the lower atmosphere (Fig.…”

mentioning

confidence: 99%

The Mars Pathfinder Atmospheric Structure Investigation/Meteorology (ASI/MET) Experiment

Schofield

Barnes

Crisp

et al. 1997

Science

424

319

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close to the observed value 29sin(ᐉ ϩ 241°) mas. 23. We thank the Mars Pathfinder project team for their enthusiasm and assistance in acquiring and understanding the tracking measurements; R. Wimberly for recovery of the Viking lander Doppler data; and J. Williams and an anonymous referee for helpful suggestions. The research described in this paper was carried out by the Jet Propulsion Laboratory, Califor- The Mars Pathfinder atmospheric structure investigation/meteorology (ASI/MET ) experiment measured the vertical density, pressure, and temperature structure of the martian atmosphere from the surface to 160 km, and monitored surface meteorology and climate for 83 sols (1 sol ϭ 1 martian day ϭ 24.7 hours). The atmospheric structure and the weather record are similar to those observed by the Viking 1 lander ( VL-1) at the same latitude, altitude, and season 21 years ago, but there are differences related to diurnal effects and the surface properties of the landing site. These include a cold nighttime upper atmosphere; atmospheric temperatures that are 10 to 12 degrees kelvin warmer near the surface; light slope-controlled winds; and dust devils, identified by their pressure, wind, and temperature signatures. The results are consistent with the warm, moderately dusty atmosphere seen by VL-1.The ASI/MET experiment consists of a suite of sensors designed to measure the vertical structure of the atmosphere during entry, descent, and landing (EDL) and to study martian surface meteorology and climate for the duration of the Pathfinder mission (1, 2). In situ vertical structure measurements were made only twice by the Viking entry vehicles (3), both during the daytime. In addition to adding a third profile, ASI/MET provides the first nighttime observation, giving information about the diurnal variation of vertical structure, particularly in the upper atmosphere, which is inaccessible to existing remote-sensing techniques. Both Viking landers obtained records of atmospheric pressure, temperature, and wind velocity at the surface that extended over several Mars years. More recent Earth-based, disk-averaged microwave observations have been interpreted to indicate episodic cooling of the martian lower atmosphere by about 20 K relative to the conditions observed during the Viking missions (4). By continuing the Viking record after 21 years, ASI/MET results are able to determine whether martian meteorology and climate have changed or remained stable in the late northern summer. Improved measurement sensitivity and temporal resolution (2) also reveal phenomena not seen by Viking and, together with temperature measurements at three levels, give better information on the exchange of heat and momentum between the atmosphere and the surface.

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Water Vapor Saturation at Low Altitudes around Mars Aphelion: A Key to Mars Climate?

Cited by 327 publications

References 17 publications

The Martian Atmosphere During the Viking Mission, I Infrared Measurements of Atmospheric Temperatures Revisited

The Martian Atmosphere During the Viking Mission, I Infrared Measurements of Atmospheric Temperatures Revisited

Isotopic fractionation through water vapor condensation: The Deuteropause, a cold trap for deuterium in the atmosphere of Mars

The Mars Pathfinder Atmospheric Structure Investigation/Meteorology (ASI/MET) Experiment

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