Diurnal variations in optical depth at Mars: Observations and interpretations

Viking lander camera images of the Sun were used to compute atmospheric optical depth at two sites over a period of 1 to 1/3 martian years. The complete set of 1044 optical depth determinations is presented in graphical and tabular form. Error estimates are presented in detail. Optical depths in the morning (AM) are generally larger than in the afternoon (PM). The AM-PM differences are ascribed to condensation of water vapor into atmospheric ice aerosols at night and their evaporation in midday. A smoothed time series of these differences shows several seasonal peaks. These are simulated using a one-dimensional radiative convective model which predicts martial atmospheric temperature profiles. A calculation combining these profiles with water vapor measurements from the Mars Atmospheric Water Detector is used to predict when the diurnal variations of water condensation should occur. The model reproduces a majority of the observed peaks and shows the factors influencing the process. Diurnal variation of condensation is shown to peak when the latitude and season combine to warm the atmosphere to the optimum temperature, cool enough to condense vapor at night and warm enough to cause evaporation at midday

Factors governing water condensation in the Martian atmosphere

Modeling results are presented suggesting a diurnal condensation cycle at high altitudes at some seasons and latitudes. In a previous paper, the use of atmospheric optical depth measurements at the Viking lander site to show diurnal variability of water condensation at different seasons of the Mars year was described. Factors influencing the amount of condensation include latitude, season, atmospheric dust content and water vapor content at the observation site. A one-dimensional radiative-convective model is used herein based on the diabatic heating routines under development for the Mars General Circulation Model. The model predicts atmospheric temperature profiles at any latitude, season, time of day and dust load. From these profiles and an estimate of the water vapor, one can estimate the maximum occurring at an early morning hour (AM) and the minimum in the late afternoon (PM). Measured variations in the atmospheric optical density between AM and PM measurements were interpreted as differences in AM and PM condensation

Altered Ecologies: Fire, climate and human influence on terrestrial landscapes: Terra Australis 32

Like a star chart this volume orientates the reader to the key issues and debates in Pacific and Australasian biogeography, palaeoecology and human ecology. A feature of this collection is the diversity of approaches ranging from interpretation of the biogeographic significance of plant and animal distributional patterns, pollen analysis from peats and lake sediments to discern Quaternary climate change, explanation of the patterns of faunal extinction events, the interplay of fire on landscape evolution, and models of the environmental consequences of human settlement patterns. The diversity of approaches, geographic scope and academic rigor are a fitting tribute to the enormous contributions of Geoff Hope. As made apparent in this volume, Hope pioneered multidisciplinary understanding of the history and impacts of human cultures in the Australia- Pacific region, arguably the globe’s premier model systems for understanding the consequences of human colonization on ecological systems. The distinguished scholars who have contributed to this volume also demonstrate Hope’s enduring contribution as an inspirational research leader, collaborator and mentor. Terra Australis leave no doubt that history matters, not only for land management, but more importantly, in alerting settler and indigenous societies alike to their past ecological impacts and future environmental trajectories

Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone

M-stars comprise 80% of main-sequence stars, and so their planetary systems provide the best chance for finding habitable planets, i.e.: those with surface liquid water. We have modelled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M-stars) using spectrally resolved data of the Earth's cryosphere. The gradual reduction of the albedos of snow and ice at wavelengths greater than 1 ?m, combined with M-stars emitting a significant fraction of their radiation at these same longer wavelengths, mean that the albedos of ice and snow on planets orbiting M-stars are much lower than their values on Earth. Our results imply that the ice/snow albedo climate feedback is significantly weaker for planets orbiting M-stars than for planets orbiting G-type stars such as the Sun. In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of cryospheric albedo is considered, which in turn implies that the outer edge of the habitable zone around M-stars may be 10-30% further away from the parent star than previously thought.Comment: Final accepted by Astrobiology, 20 pages (double spaced), 3 figures include

Workshop on Atmospheric Transport on Mars

On June 28-30, 1993, the Workshop on Atmospheric Transport on Mars was held in Corvallis, Oregon. The workshop was organized under the auspices of the MSATT (Mars Surface and Atmosphere Through Time) Program of NASA, and was jointly sponsored by the Lunar and Planetary Institute, Oregon State University, and the Oregon Space Grant Consortium. More than 50 scientists attended the workshop, which was the first such meeting to focus upon circulation processes in the Mars atmosphere. The timing of the workshop placed it almost on the eve of the arrival of Mars Observer at Mars, so that the presented papers gave a picture of the 'state of the art' in Mars atmospheric science just prior to the expected arrival of new data. The workshop highlighted a host of recent advances in atmospheric modeling and analysis - advances that will be relevant to any future observations

Landing site considerations for atmosphere structure and meteorology

The goal of the ASI/MET experiments is to extend our knowledge of Mars atmosphere structure and meteorology over that established by the Viking mission. The two in situ soundings of Mars atmosphere by Vikings 1 and 2 were highly similar, but radio occultations and infrared soundings have shown large variability in atmosphere structure on Mars with latitude, season, and terrain elevation. It would be of great interest to obtain an in situ sounding showing strong contrast in thermal structure with the Viking profiles. These would be expected to occur in the winter season, in the southern hemisphere, or at polar latitudes. These options are ruled out by Pathfinder Mission constraints, which place the entry in low, northern latitudes in mid summer, with small seasonal difference from the two Viking landers, and small latitude difference from Viking 1

Assessment of soil electrical conductivity using remotely sensed thermal data

ArticleDetection of heterogeneity (crop, soil, etc.) gained a lot of importance in the field of site - specific farming in recent years and became possible to be measured by different sensors. The therma l spectrum of electromagnetic radiation has a great potential today and experiments focused on describing a relation between canopy temperature and various vegetation characteristics are conducted. This paper was aimed to examine the relation between canop y temperature and electrical conductivity as one of staple soil characteristics. The related experiment was undertaken in Sojovice, Czech Republic, within an agricultural plot where winter wheat was grown in 2017 growing season. The examined plot was compo sed of three sub plots and 35 control points were selected within this area which the data were related to. A canopy was sensed by UAV (eBee carrying thermoMAP (FLIR TAU2) camera). Soil conductivity data were collected by terrestrial sampling using EM38 - MK 2 Ground Conductivity Meter in 1 m depth and 2 m sampling point distance. This dataset was later interpolated using the kriging method. The correlation analysis results showed a strong negative correlation between conductivity and thermal data ( - 0.82; p < 0.001 ). When comparing conductivity with NDVI representing the aboveground biomass, there was an opposite trend but also strong result (0.86; p < 0.001 ). Correlation coefficient of thermal data and NDVI comparison was - 0.86; ( p < 0.001 ). These preliminary results have a potential for further research in terms of soil characteristics studies

Stationary eddies in the Mars general circulation as simulated by the NASA-Ames GCM

Quasistationary eddies are prominent in a large set of simulations of the Mars general circulation performed with the NASA-Ames GCM. Various spacecraft observations have at least hinted at the existence of such eddies in the Mars atmosphere. The GCM stationary eddies appear to be forced primarily by the large Mars topography, and (to a much lesser degree) by spatial variations in the surface albedo and thermal inertia. The stationary eddy circulations exhibit largest amplitudes at high altitudes (above 30-40 km) in the winter extratropical regions. In these regions they are of planetary scale, characterized largely by zonal wavenumbers 1 and 2. Southern Hemisphere winter appears to be dominated by a very strong wave 1 pattern, with both waves 1 and 2 being prominent in the Northern Hemisphere winter regime. This difference seems to be basically understandable in terms of differences in the topography in the two hemispheres. The stationary eddies in the northern winter extratropics are found to increase in amplitude with dust loading. This behavior appears to be at least partly associated with changes in the structure of the zonal-mean flow that favor a greater response to wave 1 topographic forcing. There are also strong stationary eddy circulations in the tropics and in the summer hemisphere. The eddies in the summer subtropics and extratropics arc substantially stronger in southern summer than in northern summer. The summer hemisphere stationary circulations are relatively shallow and are characterized by smaller zonal scales than those in the winter extratropics

Atmospheric effects on the mapping of Martian thermal inertia and thermally derived albedo

The most widely used thermal inertia data for Mars assumes the atmospheric contribution is constant and equal to 2 percent of the maximum solar insolation. Haberle and Jakosky investigated the effect of including a dusty CO2 atmosphere and sensible heat exchange with the surface on thermal inertia. We recently utilized Haberle and Jakosky's coupled surface-atmosphere model to investigate the effects of such an atmosphere on the thermally derived albedo. The thermally derived albedo is the albedo which, together with the thermal inertia, provides model surface temperatures which best match the observed temperatures. New maps are presented of thermal inertia and thermally derived albedo which incorporate dust opacities derived from IRTM data