This dissertation presents the design and operation of a high-resolution frequency-modulated continuous-wave (FM-CW) radar system to study the structure and dynamics of clear-air turbulence in the atmospheric boundary layer (ABL). This sensitive radar can image the vertical structure of the ABL with both high spatial and temporal resolutions, and provide both qualitative information about the morphology of clear-air structures and quantitative information on the intensity of fluctuations in refractive-index of air. The principles of operation and the hardware and data acquisition characteristics of the radar are described in the dissertation. In October 1999, the radar participated in the Cooperative Atmosphere-Surface Exchange Study (CASES'99) Experiment to characterize the temporal structure and evolution of the boundary-layer features in both convective and stable conditions. The observed structures include clear-air convection, boundary layer evolution, gravity waves, Kelvin-Helmholtz instabilities, stably stratified layers, and clear-air turbulence. Many of the S-band radar images also show high-reflectivity returns from Rayleigh scatterers such as insects. An adaptive median filtering technique based on local statistics has, therefore, been developed to discriminate between Bragg and Rayleigh scattering in clear-air radar observations. The filter is tested on radar observations of clear air convection with comparison to two commonly used image processing techniques. The dissertation also examines the statistical mean of the radar-measured [special characters omitted] for clear-air convection, and compares it with the theoretical predictions. The study also shows that the inversion height, local thickness of the inversion layer, and the height of the elevated atmospheric layers can be estimated from the radar reflectivity measurements. In addition, comparisons to the radiosonde-based height estimates are made. To examine the temporal and spatial structure of [special characters omitted], the dissertation presents two case studies with the measurements of remote (the FM-CW radar and Doppler lidar) and in-situ (research aircraft, kite, and radiosonde) sensors from the stable nighttime boundary layer. It also presents a unique observation of evolution of the convective and nocturnal boundary layers by the S-band radar, and provides description of the observed boundary layer characteristics with the aid of in-situ measurements by the 55m instrumented tower and radiosonde.

This dissertation analyzes the retrieval of water vapor profiles via microwave radiometry; in particular it determines the information content of spectral data and identifies optimal measurement frequencies using an information content technique. The vertical resolution and estimate variance of water vapor profiles derived from the linear inversion of atmospheric data is examined and the effects of measurement noise on these quantities is considered. The Microwave Remote Sensing Laboratory at the University of Massachusetts has developed a unique K-Band Spectral Radiometer (KSR) system that simultaneously monitors eighteen frequencies near the 22.235 GHz water vapor absorption line and is designed to retrieve atmospheric water vapor density profiles by inverting spectral radiance measurements. This system is unique in its measurement speed and breadth. The dissertation discusses calibration techniques, system parameters, and the derivation of a statistical estimation algorithm is that is applied to KSR measurements taken during a field experiment in Lamont, Oklahoma. The resulting water vapor profiles are presented, along with a comparison of in-situ and independent observations.

The Microwave Remote Sensing Laboratory (MIRSL) at the University of Massachusetts, in collaboration with The Jet Propulsion Laboratory, has developed a new radar designed to facilitate measurements of the radiative properties of clouds. Details of this new design are described with particular emphasis on improvements from previous systems. This radar system was used to collect cloud data during three experiment campaigns. During these experiments, reflectivity data from all prevalent cloud types were collected over a wide range of geographical locations. The observations were then used to examine the reflectivity vs. altitude and temperature characteristics and layer structure for various types of cloud complexes. To increase the representation of tropical cirrus clouds in the composite data set, the airborne data was supplemented with data from MCTEX collected by the UMass CPRS radar. All observations were classified into four classes of clouds and histograms of altitude and temperature vs. reflectivity were used to demonstrate the reflectivity characteristics of various clouds types. Statistics of layer base and top altitudes, thickness and number of layers were also computed. Also, the relationship between cirrus cloud thickness, reflectivity and ice water path (IWP) is examined. The data sets from the four experiments were then used to address performance issues for a spaceborne radar. The problem of cloud detectability is discussed and an analysis of the ice water content (IWC) estimation error resulting from spatial inhomogeneity is presented. The fraction of clouds thinner than one range gate of the CloudSat radar was found to be 14% for all data sets combined. The data sets are used to simulate satellite radar pixels and the distributions of errors in IWC estimates due to inhomogeneity are calculated. On average, 40% of the pixels were partially filled and the relative IWC error was 24%. The distribution of the relative errors vs. IWC values indicated that the largest relative error occurred at vary small values of IWC and the mean error for all experiments was only 15% for IWC values larger than 10 –3 gm3.

Rapid climate change is driving increases in tundra vegetation productivity and altering the frequency and severity of natural disturbances across the Arctic. While tundra vegetation change has been widespread, there is still uncertainty about the influence of fine-scale factors on change and the role of interactions between warming, disturbance, and vegetation change. In my MSc research I investigated how Arctic tundra vegetation is responding to ongoing climate change and more severe tundra fire in the western Canadian Arctic. In the first part of my thesis I measured post-fire soil and vegetation recovery along a burn severity gradient at six fires, which burned in 2012 in the Northwest Territories. My observations suggest that deciduous shrub communities (dominated by Betula glandulosa) are resilient to high severity fire and that severe fire promotes edaphic conditions that favor the persistence of this vegetation type. In the second part of my thesis, I investigated the spatial patterns of trends in tundra vegetation productivity over the past three decades using Random Forests machine learning to analyze Enhanced Vegetation Index (EVI) data derived from Landsat imagery. My Random Forests models of the relationship between Landsat EVI trends and biophysical variables showed that two-thirds of the western Canadian Arctic productivity has increased during the past three decades and that this change is occurring most rapidly in dwarf and upright shrub-dominated regions. Taken together, my research demonstrates that shrub tundra communities are well adapted to severe fire and show increasing productivity in response to warming Arctic temperature. My research also indicates that these relationships can be highly complex at finer scales, where they are mediated by local variations in microclimate, topography, and moisture. / Graduate

Synthetic aperture radar polarimetry is one of the current developments in the field of remote sensing, due to the ability of delivering more information on the physical properties of the surface. It is known as the science of acquiring, processing and analysing the polarisation state in an electromagnetic field. The increase of information with respect to scalar radar comes at a price, not only for the high cost of building the radar system and processing the data or increasing the complexity of the design, but also for the amount of effort needed to calibrate the data. Synthetic aperture radar polarimetric calibration is an essential pre- processing stage for the correction of distortion interference which is caused by the system inaccuracies as well as atmospheric effects. Our goal, with this thesis, is to use multiple passive point targets to establish the difference between fully, and compact polarimetric synthetic aperture radar systems on both calibration, and the effects of penetration. First, we detail the selection, design, manufacture, and deployment of different passive point targets in the field for acquiring X- and P-band synthetic aperture radar data in the Netherlands. We started by presenting the selection and design of multiple passive point targets. These were a combination of classic trihedral and dihedral corner reflectors, as well as gridded trihedral and dihedral corner reflectors. Additionally, we detailed the construction of these corner reflectors. The number of constructed corner reflector totalled sixteen, where six are for X-band and six for P-band, as well as four gridded corner reflectors for X-band. Finally, we present the deployment of the corner reflectors at three different sites with carefully surveyed and oriented positions. a Then, we present the calibration of three different fully polarimetric synthetic aperture radar sensors. The first sensor is the L-band synthetic aperture radar sensor and we acquired data using two square trihedral corner reflectors. The calibration includes an evaluation of two crosstalk methods, which are the Quegan and the Ainsworth methods. The results showed that the crosstalk parameters for the Quegan method are all between -17 dB to -21 dB before calibration, while there is a small improvement in the range of 3 dB after calibration. While the Ainsworth method shows around -20 dB before calibration, and around -40 dB after calibration. Moreover, the phase, channel imbalance, and radiometric calibration were corrected using the two corner reflectors. Furthermore, the other two synthetic aperture radar sensors are X- and P-band synthetic aperture radar sensors, and we acquired polarimetric data using our sixteen corner reflectors. The calibration includes the crosstalk estimation, and correction using the Ainsworth method and the results showed the crosstalk parameters before calibration for X-band are around -23 dB, and they are around -43 dB after calibration, while crosstalk parameters before calibration for P-band are around -10 dB, and they are around -30 dB after calibration. The calibration also includes the phase, channel imbalance, and radiometric calibration, as well as geometric correction and signal noise ration measurement, for both X- and P-band. Next, we present the performance of gridded trihedral and dihedral corner reflectors using an X-band synthetic aperture radar system. The results showed both gridded trihedral and dihedral reflectors are perfect targets for correcting the amplitude compared to classical corner reflectors; however, it is not possible to use the gridded reflectors to correct the phase as we need a return from two channels to have a zero-phase difference between the polarisation channels H - V. Furthermore, we detail the compact polarimetric calibration over three com- pact polarimetric modes using a square trihedral corner reflector for the X-band dataset. The results showed no change in the π/mode while a 90ᵒ phase bias showed in the CTLR mode. Finally, the DCP mode showed a 64.43° phase difference, and it was corrected to have a zero phase, and the channel imbalance was very high at 45.92, the channels were adjusted to have a channel imbalance of 1. b Finally, an experiment to measure the penetration and reduction of P-band signal from a synthetic aperture radar system was performed using two triangular trihedral corner reflectors. Both of them have 1.5 m inner leg dimensions. The first triangular trihedral corner reflector was deployed in a deciduous grove of trees, while the other one was deployed a 10 m distance away on a grass covered field. After system calibration based on the reflector in the clear, the results showed a reduction of 0.6 dB in the HH channel, with 2.28 dB in the W channel. The larger attenuation at W is attributable to the vertical structure of the trees. Additionally, we measured the polarimetric degradation of the triangular trihedral corner reflector immersed in vegetation (trees). Further, after calibration, the co-polarisation phase difference is zero degrees for the triangular corner reflector which was outside the trees, and 62.85ᵒ for the corner reflector inside the trees. The designed and fabricated X- and P-band SAR can work operationally with the calibration parameters obtained in this thesis. The data generated through the calibration experiments can be exploited for further applications.

This dissertation focuses on the development of a digital transceiver system for a dual-band, polarimetric radar, which is to form part of the NeXtRAD multistatic radar. NeXtRAD is being developed as an instrument for research into the behaviour of clutter and targets as observed by multistatic radars. The Pentek Cobalt model 71621 software defined radio interface was procured for use as the digital transceiver in the system. The goal was to develop the software needed to use this product as the digital transceiver in a prototype version of the NeXtRAD active node, and to ensure that it could be readily integrated with other subsystems in the final system. The active node is essentially a monostatic pulse-doppler radar. Laboratory tests of the transceiver showed that it was possible to generate and digitize pulsed waveforms at a 125 MHz intermediate frequency which is used by the existing receiver exciter in the system. After extensive laboratory testing and development, phase coherent waveform generation and multichannel digitization was achieved. A low transmit power version of the active node was constructed and tested at both operating frequencies. Equipment used in the testing and development of the digital transceiver included laboratory signal generators, spectrum analyzers and oscilloscopes. The digital transceiver was able to function at pulse repetition rates exceeding 2 kHz, with a single transmit channel and three receive channels active. The lowpowered monostatic prototype system was constructed to test the digital transceiver using a receiver exciter subsystem, RF amplifiers and antennas. This prototype radar was used to take measurements of targets at ranges below 300 m and successfully detected reflections from large structures. Cars and pedestrian traffic were detected by their doppler shifts at both L- and X-band frequencies. The detection of moving and stationary targets confirmed the suitability of the digital transceiver for use in the envisioned multistatic radar system.

This study explores whether or not tropical cyclone (TC) structure information may be retrieved from satellite total ozone observations and how to link total ozone with analysis fields for potential application to TC vortex initialization schemes. Satellite total ozone retrievals from the Atmospheric Infrared Sounder (AIRS), the second Global Ozone Monitoring Experiment (GOME-2), the Ozone Monitoring Instrument (OMI), and the Ozone Mapping and Profiler Suite (OMPS) are used in this study. The study is divided into two portions: updating the quality control (QC) scheme for the AIRS total ozone data and examining applications of total ozone data in TC analyses. A modified QC scheme for AIRS total ozone is proposed to identify erroneous data while avoiding removal of potential useful data, as well as to keep the data consistent with a numerical prediction model. The modified QC scheme produces smaller bias and standard deviation of total ozone relative to the original AIRS QC scheme with less data being removed. Since ultraviolet (UV) retrieved total ozone generally suffers less cloud contamination, GOME-2 total ozone is used to examine possible TC structures captured by the data. All the TCs in the 2010-2012 Atlantic Hurricane seasons are used. Detailed comparisons of total ozone from GOME-2 and geopotential heights on isentropic surfaces from the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis are carried out for the representative case of Hurricane Earl (2010). It is shown that GOME-2 total ozone can capture the characteristics of the storm center including the eye region and spiral bands. Changes in total ozone can also reveal the variations of the storm intensity. Alternatively, locally elevated total ozone in the hurricane eye region can be used to identify the upper tropospheric storm center, depending on the stage and the radius of the maximum winds of the storm. Further, the distribution of total ozone shows that the isentropic geopotential heights may have misplaced the vortex center. Total ozone and the 'aligned' geopotential heights at isentropic levels tend to form a linear relationship. Total ozone and geopotential heights correlate better in isentropic level range of 330K to 345K than at other isentropic levels, indicating better inference of the geopotential heights from total ozone at these isentropic levels. Stronger storms tend to have larger correlations of total ozone and geopotential heights at nearly all isentropic levels examined in this study. Inter-satellite calibration is shown to be necessary for better use of ozone observations in TC applications. A general inter-satellite total ozone calibration is carried out during August of 2012 with total ozone data from the four instruments. Total ozone from different instruments shows a dependence on cloud fraction, solar zenith angle (SZA), geo-location, and possibly aerosols. Overall, GOME-2, OMI and OMPS ozone observations agree well globally for both clear-sky and cloudy conditions, whereas AIRS shows large relative differences in both the southern Polar Regions and in the 30S-30N tropical regions. The large relative errors in the southern Polar Regions are associated with large AIRS SZAs, while the large relative errors in the 30S-30N zone may be caused by aerosol contamination and high cirrus clouds. Latitudinally varying coefficients are derived to remove large, zonally varying biases. Hurricane Michael (2012) is chosen to illustrate the resulting impacts of the inter-satellite total ozone calibrations on an individual TC's structure information. It is shown that the transformed observations are more comparable spatially and radially than the original ones. The impacts of the calibrated total ozone on the regression models linking isentropic geopotential heights and total ozone formed from all the TCs are examined. The calibration improves the performance of AIRS regression models at nearly all isentropic levels by increasing the explained variance and decreasing the root-mean-square-error (RMSE), while it does not change much with the regression models for OMI and GOME-2. Overall, stronger storms tend to have larger inference of geopotential heights at all the isentropic levels from these total ozone observations before and after the inter-satellite calibration. The inter-satellite total ozone calibration improves the comparability among different regression models. The resulting more consistent regression models based on TC's intensities can provide more consistent initial analysis fields from different total ozone observations for potential hurricane vortex initialization application. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Spring Semester, 2015. / April 9, 2015. / Includes bibliographical references. / Robert Ellingson, Professor Directing Dissertation; Xiaoming Wang, University Representative; Robert Hart, Committee Member; Vasubandhu Misra, Committee Member; Guosheng Liu, Committee Member.

Tropical cyclone intensity prediction is an issue at the forefront of mesoscale numerical weather prediction efforts because it is an area where historically there have been only small improvements, and yet much more progress is needed to improve advance warnings for land- falling tropical cyclones (TCs). In recent years, research instrumentation has been developed for deployment aboard aircraft that remotely study tropical cyclones in order to answer critical intensity questions about TCs. One such instrument is the NASA Hurricane Imaging Radiometer (HIRAD) that has been developed to observe hurricane surface wind speeds and rain rates. This study explores the expected benefits of this instrument's data to numerical simulations of tropical cyclones using two different data assimilation methods within the experimental framework of Observing System Simulation Experiments (OSSE). The HIRAD instrument performed its inaugural hurricane flights during the summer 2010 NASA Genesis and Rapid Intensification Processes (GRIP) field program, when it first studied Hurricane Karl undergoing Rapid Intensification (RI) during its brief transit over the southern Gulf of Mexico. RI events such as this one are particularly difficult to forecast given the short duration and distance over water between landmasses. The aims of this study are four-fold: first, the creation of two Nature Run simulations of Hurricane Karl as a strong and a weak hurricane; second, the accurate simulation of the HIRAD instrument's rain rate and wind speed observations; third, the development and use of two data assimilation schemes for use with the Weather Research and Forecasting (WRF) model using simulated HIRAD data for both Nature Runs; and fourth, the improvement of Hurricane Karl's intensity forecast at the end of the data assimilation period due to the inclusion of HIRAD observations and potential use for aiding the forecast of landfalling intensity. The two data assimilation schemes in this study include the creation of an update to the Krishnamurti et. al, technique of Physical Initialization of rain rates for a mesoscale model, and the adjustment and use of an Ensemble Kalman Filter (EnKF) data assimilation scheme developed by Zhang et al. for use with tropical cyclone wind speeds. Additionally, since HIRAD currently flies in the NASA HS3 field campaign on the same Global Hawk as the NASA High-altitude Radar (HIWRAP)- a dual-frequency, dual-beam conical scanning Doppler radar system- a few OSSE experiments are performed combining simulated data from both instruments. These assess the potential benefits of assimilating HIRAD wind speeds alongside HIWRAP radial velocities to further improve the initialization of TC intensity. / A Dissertation submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester, 2014. / November 12, 2014. / data assimilation, EnKF, HIRAD, OSSE, rain rate initialization / Includes bibliographical references. / T. N. Krishnamurti, Professor Co-Directing Dissertation; Guosheng Liu, Professor Co-Directing Dissertation; Eric Chassignet, University Representative; Robert Ellingson, Committee Member; Vasu Misra, Committee Member.

MENVSC (Ecology and Resource Management) / See the attached abstract below

Mineral detection and geological mapping through conventional ground survey methods based on field observation and other geological techniques are tedious, time-consuming and expensive. Hence, the use of remote sensing in mineral detection and lithological mapping has become a generally accepted augmentative tool in exploration. With the advent of multispectral sensors (e.g. ASTER, Landsat and PlanetScope) having suitable wavelength coverage and bands in the Shortwave Infrared (SWIR) and Thermal Infrared (TIR) regions, multispectral sensors, along with common and advanced algorithms, have become efficient tools for routine lithological discrimination and mineral potential mapping. It is with this paradigm in mind that this project sought to evaluate and discuss the detection and mapping of magnetite on the Eastern Limb of the Bushveld Complex, using specialized common traditional and machine learning algorithms. Given the wide distribution of magnetite, its economic importance, and its potential as an indicator of many important geological processes, the delineation of magnetite is warranted. Before this study, few studies had looked at the detection and exploration of magnetite using remote sensing, although remote sensing tools have been regularly applied to diverse aspects of geosciences. Maximum Likelihood, Minimum Distance to Means, Artificial Neural Networks, Support Vector Machine classification algorithms were assessed for their respective ability to detect and map magnetite using the PlanetScope Analytic Ortho Tiles in ENVI, QGIS, and Python. For each classification algorithm, a thematic landcover map was attained and an error matrix, depicting the user's and producer's accuracies, as well as kappa statistics, was derived, which was used as a comparative measure of the accuracy of the four classification algorithms. The Maximum Likelihood Classifier significantly outperformed the other techniques, achieving an overall classification accuracy of 84.58% and an overall kappa value of 0.79. Magnetite was accurately discriminated from the other thematic landcover classes with a user’s accuracy of 76.41% and a producer’s accuracy of 88.66%. Despite the Maximum Likelihood classification algorithm illustrating better class categorization, a large proportion of the mining activity pixels were erroneously classified as magnetite. However, this observation was not merely limited to the Maximum Likelihood classification algorithm, but all image classifications algorithms. The overall results of this study illustrated that remote sensing techniques are effective instruments for geological mapping and mineral investigation, especially in iron oxide mineralization in the Eastern Limb of Bushveld Complex. / Dissertation (MSc)--University of Pretoria, 2019. / Geology / MSc / Unrestricted