An observational program was designed for systematic spatial and temporal monitoring of the Jovian atmosphere at several wavelengths chosen for their different absorptive properties. The weak broadband (5Å/pixel) CH₄ absorptions (6190 and 7270Å) probe the deep (2-4 bars) cloud layer while the stronger band at 8900Å probes the upper 400-600 mbars. The high resolution (~50mÅ/pixel) 3-0 H₂ quadrupole wavelengths probe to about 1-2 bars. The gradual increase in the measured equivalent widths of the H₂ quadrupole lines from the east to west limb is most likely indicative of a diurnal change in the vertical cloud structure. Such a variation is consistent with the properties of a convective layer driven by internal heat, with solar heat deposited at the top. The CH₄ data from the same time period was modelled for the south tropical zone. Since these absorptions are sensitive to several atmospheric layers it is difficult to separate the effects of the various cloud parameters on the [(I/F)(band)]/[(I/F)(cont)] values. There are no obvious limb to limb variations in these bands but several cloud parameters may be changing simultaneously, introducing compensating affects on the [(I/F)(band)]/[(I/F)(cont)] values. The two limbs may not, therefore, appear significantly different even if they are representative of substantially different cloud structures. The June 1983 H₂ data has been modelled at seven different latitudes and cloud structure differences are indicated. The average models representing the belt regions require somewhat thinner optical depths for the upper ammonia cloud (τ(cl) = 3-4.5) than the zones (τ(cl) = 5.5-6.5) or the equatorial region (τ(cl) = 6.5-7). These data also provide some constraints on the thermodynamic state of the hydrogen. A model atmosphere with only "normal" hydrogen (ortho-H₂ to para-H₂ of 3:1) is not able to fit both of the 3-0 lines simultaneously. Model atmospheres with all of the hydrogen in a state of equilibrium fit the two lines much better. Models with small amounts of disequilibrium hydrogen in the upper atmosphere also provide reasonable average fits to our H₂ data and cannot be easily distinguished from those that incorporate only equilibrium hydrogen at all levels or from those which incorporate "normal" in the top 300 mbars of the Jovian atmosphere.

The Penn-State/NCAR MM5 mesoscale model was adapted for mesoscale simulations of the Martian atmosphere (the OSU MMM5). The NASA Ames Mars GCM provides initial and boundary conditions. High-resolution maps for albedo, thermal inertia and topography were developed from Mars Global Surveyor (MGS) data; these baseline maps are processed to appropriate resolutions for use in the GCM and the mesoscale model. The OSU MMM5 is validated in Chapter 2 by comparing with surface meteorology observed at the Viking Lander 1 (VL1) and Mars Pathfinder (MPF) landing sites. How the diurnal cycle of surface pressure (the surface pressure tide) is affected by boundaries, domain/nest choices and the resolution of surface properties (topography, albedo and thermal inertia) is examined. Chapter 2 additionally shows the influence of regional slope flows in the diurnal surface pressure cycle for certain locations on Mars. Building on the methods of Chapter 2, Chapter 3 describes the northern midsummer polar circulation and the circulations (both large and small scale) that influence it. Improvements to the model for these studies include: the topographical gradient is now considered when computing surface insolation, and the thermal inertia maps and model initialization are improved for high latitudes; this yields a realistic simulation of surface temperatures for the North Pole Residual Cap (NPRC) and the surrounding region. The midsummer polar circulation is vigorous, with abundant and dynamically important transient eddies. The preferred locations of transients varies significantly during this study, between L[subscript s]=l20 and L[subscript s]=l50. At L[subscript s]=l20 transient circulations are seen primarily along the NPRC margin, consistently producing strong flow over the residual cap (~l5 m/s). By L[subscript s]=135, transient eddies form a "storm track" between the northern slopes of Tharsis and the NPRC. By L[subscript s]=150, the circulation is becoming strong and winter-like. These transient eddies may be important in the Martian annual water cycle; many of the observed circulations are poorly (or not) simulated in present day Mars GCMs. Increased resolution and polar stereographic domains provide improvement over GCMs for high latitude studies of atmospheric circulations. These results are in agreement with recent observations. Future work includes model refinements and water vapor transport studies. / Graduation date: 2005

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Mariner 9 and Viking spacecraft observations during the 1970's have provided evidence for planetary-scale wave-like disturbances in the Mars atmosphere. It has been suggested that possible sources of the wave activity are dynamical instabilities (e.g., barotropic and/or baroclinic instabilities). An other candidate source is forced, quasi-stationary planetary waves. In connection with Mars' enormous relief, both mechanical forcing and large-scale thermal contrasts due to spatially varying surface thermal-inertia and albedo patterns should provide a strong source for planetary-wave activity. In this thesis, we attempt to model aspects of the observed wave activity, focusing on forced planetary waves in the wintertime atmosphere of Mars. Our approach is to apply two dynamical models: a linear primitive equations model and a quasi-linear 'wave, mean-flow' model. Both models have spherical geometry and represent deviations from zonal symmetry in terms of Fourier modes. The former model permits a separation of responses to different elements that make up the total forcing mechanism, whereas the latter is used principally to investigate the role forced planetary waves may play in the Mars polar warming phenomenon. Basic states representing relatively 'non-dusty' and 'highly dusty' conditions near winter solstice allow wavenumber-1 and -2 disturbances to propagate meridionally and vertically into the winter jet. Higher wavenumbers are strongly vertically trapped. Stationary waves in the northern and southern extratropics differ strongly in amplitude, phase and horizontal wave pattern. The possibility for near-resonant, long-period modes in Mars' winter atmosphere is also examined. For several wave-amplitude measures and dissipation strengths, dusty low-frequency responses are an order of magnitude larger than non-dusty ones. Wave, mean-flow simulations using wavenumber-1 or -2 forcings indicate north polar warmings can occur for the dusty basic states. The sensitivity (magnitude, location, and time scale) of a simulated warming to the wave forcing and the dissipation strength is investigated. / Graduation date: 1993

Pioneer 10 and 11 polarimetry maps of Jupiter, taken at a wide variety of phase angles, have been analyzed. Data were reduced in two colors for Jupiter's South Equatorial Belt (latitude -5 to -8 degrees) and scattering models were constructed. Variations in polarization from center to limb set constraints on the vertical structure of the atmosphere. The absolute polarization near the center of the disc constrained the single scattering polarization phase matrix of the scattering particles. After exploring several types of cloud models, it was found that a two cloud model with a haze in the upper atmosphere fits the data best. Several types of vertical structures were ruled out, including gas over a nonpolarizing Lambert surface, gas over a polarizing cloud deck, uniformly mixed gas with scattering particles (Reflecting Scattering Model), and models where the cloud tops diffusely mixed with gas as a function of altitude. Constraints have been set upon the polarimetric scattering properties of the haze and lower clouds. The haze particles are closely approximated by conservatively scattering spheres of index of refraction 1.5 and uniformly distributed sizes between 0.16 and 0.18 microns radius. A relationship exists between the required index of refraction for the haze particles and the mean size of the particles. It is possible that the particles are more broadly distributed in size, as this area was not extensively explored. The optical depth of the haze is between 0.125 and 0.250 at a wavelength of 0.44 microns, and lies near the 200 millibar pressure level. The upper cloud, which is thought to be made of ammonia crystals, must be at least optical depth 2, and could be semi-infinite. The polarization scattering properties of the clouds are distinctly different from the haze, indicating a compositional or size difference. The cloud particles have polarizing properties indicative of large (larger than 0.5 micron radius) particles. The upper cloud has been modelled to be near the 500 millibar level, but the pressure level for the best fitting model depends upon the chosen single scattering phase matrix. For more negatively polarizing cloud particles, the cloud would be located deeper in the atmosphere. The lowest cloud is more weakly constrained. Its scattering properties are set the same as the upper cloud, and it has been modelled as having semi-infinite optical depth. For the nominal scattering phase matrix, this cloud is located near the 2250 millibar pressure level. The constraints set on both the vertical structure and the particle scattering properties can be useful in the determination of Jupiter's solar flux deposition profile. Additionally, the location of the cloud and haze layers in Jupiter's atmosphere is important to the understanding of the heat balance of the planet, as well as to the understanding of the global dynamic of Jupiter's atmosphere.

Researchers analyzing the upper clouds of Jupiter and Saturn are unable to theoretically reproduce the data returned by Pioneers 10 and 11 and Voyagers 1 and 2 with an approach based on Mie theory. Ammonia crystals are believed to be an important constituent of Jupiter's upper clouds, but both their shape and scattering properties were unknown at the start of this work. Ammonia crystals and water crystals were grown in a cold chamber at temperatures 20°C below their freezing points (0°C and -77.7°C, respectively). The H₂O crystals formed had shapes in agreement with published growth habit diagrams. The NH₃ crystals formed were usually irregular in shape, but regular four-sided pyramids were commonly observed. This four-sided pyramidal shape is in agreement with ammonia's primitive cubic crystal structure. Ammonia crystals could not be formed at temperatures above -95°C due to nucleation problems. A scattering measuring instrument was constructed with fifteen separate lens-detector combinations aimed at a common point in the center of the cold chamber. A laser beam (6328Å wavelength) traversed the chamber center, illuminating any crystal aerosal clouds present. A computer was used to rapidly sample the outputs of the fifteen detectors and to drive a photoelectric modulator to change the slow speed polarization properties of the laser beam. The measurements resulted in a determination of the single scattering phase function and degree of linear polarization for the crystal species present. Water crystals were found to have scattering properties similar to that reported by previous researchers. The H₂O crystal scattering possesses a smaller backscatter peak and smaller polarization features than is common for water spheres of similar size. A negative polarization of 5% occurred in the forward scattering hemisphere and a positive polarization of 10% in the rear. Ammonia particles were observed to have a backscattering peak four times higher than for water crystals. The NH₃ particle light scattering produced very little polarization of the scattered light. A small (∼ 4%) negative polarization occurred in the forward scattering hemisphere. Work is continuing here to make scattering measurements using blue light illumination nearly simultaneous with the red HeNe laser wavelength illumination.

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