An efficient and simple method has been developed to improve quality and accuracy of satellite-based VIS/IR images through cloud-top relief spatial displacements adjustment. The products of this algorithm, including cloud-top temperatures and heights, atmospheric temperature profiles for cloudy sky, and displacement-adjusted cloud images, can be useful for weather/climate and atmospheric studies, particularly for high-resolution hydrologic applications such as developing IR satellite-based rainfall estimates, which are urgently needed by mesoscale atmospheric modeling and studies, severe weather monitoring, and heavy precipitation and flash flood forecasting. Cloud-top height and displacement are estimated by applying stereoscopic analysis to a pair of corresponding scan-synchronous infrared images from geostationary satellites (GOES-east and GOES-west). A piecewise linear approximation relationship between cloud-top height and temperature, with a few (6 and 8) parameters is developed to simplify and speed-up the retrieval process. Optimal parameters are estimated using the Shuffled Complex Evolution (SCE-UA) algorithm to minimize the discrepancies between the brightness temperatures of the same location as registered by two satellites. The combination of the linear approximation and the fast optimization algorithm simplifies stereoscopic analysis and allows for its implementation on standard desktop computers. When compared to the standard isotherm matching approaches the proposed method yields higher correlation between simultaneous GOES-8 and GOES-9 images after parallax adjustment. The validity of the linear approximation was also tested against temperature profiles obtained from ground sounding measurements of the TRMM-TEFLUN experiments. This comparison demonstrated good fit between the optimized relationship and atmospheric sounding profile. The accuracy of cloud pixel geo-location was demonstrated through a spatial comparison between correlation of ground-based radar rainfall rate and corresponding both adjusted and original satellite IR images. Higher correlation was represented using displacement-adjusted IR images from both geostationary satellites (GOES) with high altitudes and low altitude satellite (TRMM). Higher correlation and lower RMSE between ground-based NEXRAD observations and estimated rainfall rates from spatial adjusted IR images, using an artificial neural networks algorithm (PERSIANN), present the rainfall retrieval improvement. The ability to differentiate ground surface particularly snow-covered areas from clouds in near-real-time is another useful application of estimated cloud-top height.

A new spherical-shell radiative transfer model has been developed, with particular emphasis on the accurate calculation of the scattered radiance in the limb of the atmosphere. The model accounts for the spherical geometry of the atmosphere for all orders of scattering, but neglects the influence of polarization and refraction. Solutions are obtained by the successive orders of scattering method for several solar zenith angles simultaneously, using the inherent symmetry of the radiation field about the sub-solar point. The model is described by comparing and contrasting it with the model previously presented by Thome (1990) and Herman et al. (1994). The new model is tested against independent calculations to demonstrate the accuracy of the method. Its results are compared with the Monte Carlo calculations presented by Adams and Kattawar (1978) and Kattawar and Adams (1978) for a homogeneous atmosphere. Agreement is observed to within the stated statistical error of the Adams and Kattawar (1978) and Kattawar and Adams (1978) results for all lines of sight, including those in the limb. Comparisons are also made to the results obtained by the Herman et al. (1994) code for a more realistic atmospheric profile. These comparisons reveal excellent agreement outside the limb of the atmosphere, but some significant disagreement in the limb, which must be investigated further. Finally, preliminary results are presented that demonstrate the sensitivity of limb scattered radiances to changes in the ozone profile. Limb radiances are shown to be sensitive to a relatively small change in the ozone abundance in a thin layer of the atmosphere. However, the observed sensitivity is shown to decrease when aerosol scattering is added to the model atmosphere.

The primary objective of this research is to investigate relationships between extremes in central Sierra Nevada tree growth, temperature and precipitation and winter and summer atmospheric circulation. Using existing Sierra Nevada chronologies, I developed two mean chronologies for the period of overlap between instrumental and tree-ring records (1900-1987), one for giant sequoia (Sequoiadendron giganteum) and one for treeline pines (Pinus balfouriana, Pinus albicaulis) and selected the highest and lowest quintiles of tree growth as extreme years. For these years, I constructed and analyzed maps of composite anomalies for the following climatic data: tropospheric pressure (SLP, 700 mb, 500 mb), storm track (positive vorticity advection [PVA], a variable not previously used in dendroclimatology), temperature, precipitation, and snow (a variable often assumed have the same effects on growth as winter precipitation). Results suggest that extreme growth in these trees is associated with distinct patterns of winter atmospheric circulation and snow depth that are consistent with instrumental studies for the Western U.S. The storm track and snow analyses, seldom used in dendroclimatology, added substance to inferences based on analyses of tropospheric and surface climate parameters. This study shows the strong potential for reconstruction of these variables using Sierra Nevada trees. Synthesis of these results suggests that sequoia exhibit low growth during years with meridional winter and summer circulation, winter storms primarily occluded in the Gulf of Alaska, and low snow depth; sequoia exhibit high growth during years with low winter pressure in the north Pacific, long duration storms, a SW-NE oriented storm track entering North America at the California-Oregon border, high snow depth and zonal summer flow. Treeline pines exhibit low growth during years with enhanced ridging over the eastern Pacific, cool, short duration winter storms along a northern track, low snow depth and high east Pacific summer SLP; these pines exhibit high growth during years with warm, long duration winter storms following a southern track, a quasi-PNA atmospheric circulation pattern, average snow depth and a northeastward displaced summer subtropical high. Evidence presented herein suggests that variation in extreme treeline pine growth tracks low frequency changes in north Pacific atmospheric circulation.

The properties of aerosol dust on Mars may be deduced from photometric observations of its atmosphere. By comparing sky images taken by the Imager for Mars Pathfinder to numerical models, the size distribution and reflective properties of the dust particles can be determined. The format, quality, and reduction of the IMP images is described herein, as is the computational radiative transfer model used, with its various parameters. After discovering and compensating for an imprecision in the pointing of the camera, models were successfully fit to the IMP solar aureole datasets. Key results include determining the particle size (reff = 1.6 ± 0.15 μm); quadratic parameters G and Θmin describing the phase function for internally scattered light as functions of wavelength; and the imaginary refractive index n i (and single scattering albedo o) of the aerosols as a function of wavelength (presented in Table 4.1). Preliminary indications of temporal variation in ni turn out to be due to an unplanned change in the time of day of the measurements, coupled with a limitation in the algorithm for correcting the aforementioned pointing imprecision. Excluding unreliable datasets leads to a set of particle properties which shows no significant variation over the first two months of the Pathfinder mission. A multispectral sky patch from MPF Sol 22 gives greater wavelength resolution, as well as showing the sensitivity of the results to variations in key model parameters. In addition, images from the Hubble Space Telescope are used to refine the surface reflectance used in the model. The final result is a model for the aerosol dust which is consistent with the IMP solar aureole observations and the HST observations. Evidence for a minor component of water ice is also discussed. Dust reflectances derived for comparison with ground spectra show a feature in the near infrared which is not present in most MPF spectra of bright surface regolith. This is an indication that there are components visible in the bright soil which are not present in the airborne dust.

Optical glint patterns convey information about the roughness of the surface on which they are formed. This dissertation describes two new optical instruments that relate the variations of specular laser reflections (laser glints) from the sea surface in angular, temporal, and wavenumber space to the surface roughness. Measurements from these instruments are interpreted with the objective of improving the capabilities of remote-sensing instruments that view the ocean surface. Particular attention is paid to cm waves, which are resonant structures for microwave sensors and the most significant component of optical roughness. The scanning-laser glint meter counts laser glints in 1° angular bins over a ± 75° nadir-angle range. The video laser-glint imager is a CCD video camera that images glints from an array of diode lasers. Both instruments were deployed on the research platform FLIP in the Pacific Ocean near the Oregon coast for three weeks during September 1995. Normalized histograms of angular glint counts are interpreted as the probability density function (PDF) of sea-surface slope, a Gram-Charlier expansion of which facilitates studying the variation with wind speed and atmospheric stability of moments through order four. The PDF appears approximately Gaussian, but is skewed toward downwind slopes in the along-wind axis due to asymmetric wind waves. No skewness exists in the cross-wind axis. Slope PDFs also have positive peakedness, increasing the probability of very small and large slopes relative to a Gaussian. Surface roughness is shown to depend strongly on atmospheric stability, which is proportional to the air-water temperature difference. Both the mean-square slope and the peakedness increase with negative stability (water warmer than air) relative to the neutral-stability case (water and air temperatures equal). Increased surface roughness, due to increases in wind speed or negative stability, causes glint-count fractal dimensions to increase, glint-image power spectra to flatten, and glint-image autocorrelations to appear more wrinkled. Glint-image spectra are dominated by glint-size effects, which are related to surface curvature. New ways of modeling the interaction of electromagnetic waves with the ocean surface are suggested by the new fractal and spectral characterizations of surface roughness that are introduced here.

Six thunderstorms that occurred at the NASA Kennedy Space Center, Florida, have been studied in an attempt to characterize their electrical structure and electrification. Ground-based measurements of the cloud electric fields, the locations of lightning VHF radio sources, cloud-to-ground lightning strike points, and dual-polarization radar data were used in this study. Changes in the electric field due to lightning were used to determine the locations and magnitudes of changes in cloud charge. The fields themselves were used to compute displacement current densities following lightning flashes. The altitudes of negative charge regions were between 6.5 and 8.5 km and were almost constant. The altitude of upper positive charge exhibited more variability, and usually increased as cells developed. Amounts of charge removed by lightning increased during each cell in large storms but were nearly constant during the early part of small storms. A lower positive charge center (LPCC) usually appeared in the fields before any other charge regions could be detected at the ground. A LPCC appeared to be involved in the initiation of the majority of CG flashes. During periods of lightning, a LPCC was sometimes created by a flash, but more typically, LPCCs were produced by a cloud charge separation process. Displacement current densities were used to estimate charge accumulation rates in the cloud. The rates derived for the main negative and upper positive charge regions were compared to the average rate of charge removal by lightning. The generation rates and average lightning currents each had values ranging from 0.2 to 1.5 A and were approximately equal within expected errors in single-cell storms. Once the storm was multicellular, however, the lightning current was larger than the cloud charging rate, possibly because lightning was removing residual charge from older cells. The cloud charging rates and average lightning currents were compared with the currents computed using a non-inductive ice-graupel charging mechanism and radar-derived cloud microphysical data. This mechanism provided currents that were comparable to the observed charging rates and lightning currents and appeared to be capable of producing the LPCC.

A micrometeorological station was established on the sea ice at Tanquary Fiord, Northern Ellesmere Island, during the late spring and early summer period of 1964. [...]

The Pioneer Venus observations show a peak in the O$\sb2\sp+$ concentration at $\sim$170 km altitude in the dayside ionosphere of Venus. In this thesis, the 2-dimensional MHD equations are solved in a self-consistent manner, as an extension to the 1-dimensional model by Cloutier et al. (1987), to present a global model of the Venus dayside ionosphere for solar zenith angles (SZA) $\leq$ 60$\sp\circ$. The model describes, by calculating vertical profiles at different SZA, ion densities, magnetic field magnitudes, and ion velocities. The model shows that the O$\sb2\sp+$ peak, at $\sim$170 km altitude, occurs throughout the dayside ionosphere as observed by the Orbiter Ion Mass Spectrometer (OIMS). The velocity field, which affects the ion distributions, is mainly tangential near the ionopause and radial for altitudes below 200 km. The downward flow accelerates, near 170 km altitude, due to collisional interactions with the neutral atmosphere, and removes the O$\sb2\sp+$ densities to lower altitudes, thus, producing the bump observed in the altitude profile.

Strong 8-$\mu$m infrared hot spots in the polar regions of Jupiter exhibit different behaviors: the northern polar hot spot (hereafter, NPHS) tends to remain fixed in System III longitude while the southern polar hot spot (SPHS) drifts. Joule heating associated with Pedersen currents that are generated by the spinning magnetized ionosphere (the Faraday disc dynamo) is proposed as a possible power source for the hot spots. A quantitative perturbation model is used to show that the NPHS is confined by a steep longitudinal magnetic-field gradient to a System III longitude of approximately 175$\sp\circ$, in agreement with observations. The model also shows that a Joule heating power of about $10\sp{14}$-$10\sp{15}$ Watts can be dissipated in the hydrocarbon layer, significantly larger than particle-precipitation power and the radiated power of the hot spots. The drift of the SPHS is hypothesized as being caused by gravity waves. The total energy provided by Joule heating and by the dissipation of the waves constitutes the power for the hot spot; propagation of the waves causes the location of the total energy deposition to move, thus causing the drift of the SPHS. Because of the asymmetry in the polar magnetic field configurations between the two hemispheres, these gravity waves are more likely to deposit energy comparable to the Joule heating energy in the south to heat up the hydrocarbon layer where IR emission originates. The ranges of wavelength and frequency are investigated for waves that propagate mainly in north-south direction. These waves can cause the SPHS to drift at the observed speed of $\sim$5km/s and dissipate heat that is comparable to Joule heating in the south but less important than the Joule heating in the north. The current-driven joule-heating model, with the presence of wave modulation, can thus account for the primary features of the Jovian polar hot spots: their power output, the fixed location of the NPHS, and the drift motion of the SPHS.

Two experimental campaigns designed to study high-latitude auroral arcs have been conducted in Sonde Stromfjord, Greenland. The Polar Acceleration Regions and Convection Study (Polar ARCS) on February 26, 1987, consisted of a coordinated set of ground-based and sounding rocket measurements of a weak, sun-aligned arc within the duskside polar cap, while the Rodeo I and II experiments, conducted during December, 1988 and October, 1989, involved uniquely coordinated optical and radar measurements of high-latitude arcs occurring at the poleward boundary of the auroral oval. Analysis of the large-scale Polar ARCS data indicate anti-sunward convection in the region between the duskside auroral oval and the sun-aligned arc. This convection signature is consistent with either a model in which the sun-aligned arcs formed on open field lines over the polar cap or on closed field lines threading an expanded low-latitude boundary layer, but not a model in which the polar cap arc field lines map to an expanded plasma sheet. Electron measurements indicate that the rocket passed through three narrow ($\le$20 km) regions of low-energy ($\le$100 eV) electron precipitation. An electrodynamic analysis has shown the electric and magnetic field perturbations in these regions to be well correlated and associated with small-scale upward and downward field-aligned currents of 1-2 $\mu$A/m$\sp2.$ The Rodeo measurements have been used to examine the aeronomic and electrodynamic characteristics of two optically stable arcs occurring at different magnetic local times and exhibiting different relationships to the polar cap/convection reversal boundary. The first case study is associated with a reversal from antisunward to sunward flow and also the boundary between open and closed field lines. In contrast, the second case study involved an arc with a much greater average precipitation energy and a significant cross-arc flow, evidenced by the radar measurements as well as the convective motion of a polar cap patch directly across the arc. Owing to the relative motion between the F-layer plasma and the arc precipitation, this arc is interpreted as forming across the nightside merging gap on field lines which map to a region of stable reconnection in the tail.