This dissertation classifies trees, snow, and clouds using multiparameter millimeter-wave radar data at 35, 95, and 225 GHz. Classification techniques explored include feedforward multilayer perceptron neural networks trained with standard backpropagation, Gaussian and minimum distance statistical classifiers, and rule-based classifiers. Radar data products, serving as features for classification, are defined, radar and in situ data are presented, scattering phenomenology is discussed, and the effect of data biases are analyzed. A neural network was able to discriminate between white pine trees and other broader-leaved trees with an accuracy of 97% using normalized Mueller matrix data at 225 GHz; wet, dry, melting, and freezing snow could be discriminated 89% of the time using 35, 95, and 225 GHz Mueller matrix data; and metamorphic and fresh snow could be differentiated 98% of the time using either the copolarized complex correlation coefficient or normalized radar cross section at three frequencies. A neural network was also able to discriminate ice clouds from water clouds using vertical and horizontal 95 GHz airborne reflectivity measurements with a success rate of 82% and 86% when viewing the clouds from the side and below respectively. Using 33 and 95 GHz data collected from the ground, a neural net was able to discriminate between ice clouds, liquid clouds, mixed phase clouds, rain, and insects 95% of the time using linear depolarization ratio, velocity, and range. As a precursor to this classification, a rule-based classifier was developed to label training pixels, since in situ data was not available for this particular data set. Attenuation biases in reflectivity were also removed with the aid of the rule-based classifier. A neural network using reflectivity in addition to other features was able to classify pixels correctly 96% of the time.

The Engineering Research Center for Collaborative Adapting Sensing of the Atmosphere (CASA) was established to improve the coverage of the lowest portion of the atmosphere through coordinated scanning of low-power, short-range, networked radars (referred to as Distributed Collaborative Adaptive Sensing (DCAS)). The first DCAS technology demonstration test-bed has been deployed in south-west Oklahoma in early 2006: a network of four, low-power, short-range, dual polarization, Doppler radar units, referred to as IPI (after CASA’s Integrated Project 1). This dissertation is devoted to documenting the IP1 system. Special emphasis is placed on the aspects that enable coordinated radar operation and on other features that provide substantial improvements over existing approaches. In particular, the IP1 radar network can sample the atmosphere with high spatio-temporal resolution and at low altitudes. The dual polarization capabilities and simultaneous multiple radar observations of weather phenomena enable the retrieval of enhanced data products including attenuation corrected reflectivity, dual polarization parameters, and vector wind fields. In addition, the modular radar control, data processing, and communications software architecture allows variations in the network topology, control, and weather information extraction, making the extension of the network easy through the addition of potentially heterogeneous radar nodes.

This dissertation presents W-Band measurements of the copolar correlation co-efficient and Doppler spectrum taken from the University of Wyoming King Air research airplane. These measurements demonstrate the utility of making W-Band polarimetric and Doppler spectrum measurements from an airborne platform in investigations of cloud microphysical properties. Comparison of copolar correlation coefficient measurements with aircraft in situ probe measurements verifies that polarimetric measurements indicate phase transitions, and hydrometeor alignment in ice clouds. Melting layers in clouds were measured by the W-Band system on board the King Air during 1992 and 1994. Both measurements established the use of the linear depolarization ratio, LDR, to locate the melting layer using an airborne W-Band system. The measurement during 1994 allowed direct comparison of the magnitude of the copolar correlation coefficient with the values of LDR. The relation between the measurements corresponds with a predicted relationship between the two parameters for observation of particles exhibiting isotropy in the plane of polarization. Measurements of needle crystals at horizontal and vertical incidence provided further evidence that the copolar correlation coefficient values agreed with the expected response from hydrometeors possessing a preferred alignment for the side looking case, and hydrometeors without a preferred alignment for the vertical incidence case. Observation of significant specific differential phase at vertical incidence, the first reported at W-Band, corresponded to a significant increase in differential reflectivity overhead, which was most likely produced by hydrometeor alignment driven by cloud electrification. Comparison of the drop size distributions estimated using the Doppler spectra with those measured by the wingtip probes on the King Air reveals that the radar system is better suited under some liquid cloud conditions to provide microphysical measurements of the cloud or precipitation than the probes. The radiometric calibration of the radar system determines the accuracy of the drop size distribution estimate. The results presented here indicate that the procedure used to absolutely calibrate the W-Band radar system successfully characterized the reflectivity measurements to the extent required to obtain close correspondence between the radar and probe measurements of the drop size distribution.

For over 30 years, radars have examined the structure of the convective boundary layer (CBL). Those studies have consisted either of the three dimensional structure of km-scale features, or of the vertical structure of local, 1 to 100 m-scale features. A new instrument, the Turbulent Eddy Profiler (TEP), images the local, three dimensional character of the CBL with the 10 m-scale resolution of current vertically profiling systems. This thesis presents TEP CBL measurements, including $\tilde C\sbsp{n}{2}$, the local refractive index structure-function parameter, and w, the vertical velocity. Qualitative horizontal and vertical images are shown. The scales of the measured structures are then quantified through calculation of the correlation distance. To examine larger scale features, effective volumes are constructed from TEP time series data through Taylor's hypothesis. Within those volumes, the statistical properties of $\tilde C\sbsp{n}{2}$ and w and calculated. These measurements highlight some of the capabilities of the TEP system, and give a unique picture of the morphology and evolution of $\tilde C\sbsp{n}{2}$ and w in the CBL. Many of the TEP measurements are compared to appropriately scaled large-eddy simulation (LES) predictions. The LES qualitative CBL structure agrees well with the measurements, while the statistical values of $\tilde C\sbsp{n}{2}$ agree well for only some of the measured data. Those $\tilde C\sbsp{n}{2}$ comparisons are the first of their kind, however, and suggest that LES may become a useful tool in CBL propagation studies.

This dissertation presents a unique Compact Millimeter-wave Radar (CMR) developed at the University of Massachusetts Microwave Remote Sensing Laboratory (MIRSL) for measurements of clouds and precipitation. CMR is a 95 GHz solid-state radar with high resolution and Doppler capability which is intended for the eventual use on an unmanned aerospace vehicle (UAV). Details of the design are given here with emphasis on the approaches used to reduce the size and power consumption by almost an order of magnitude compared to previous cloud radars. Ground-based experiments were conducted comparing measurements of clouds and snow made with CMR to those made with the Cloud Profiling Radar System, a full-sized 95 GHz radar with greater sensitivity. The results are used to verify the performance of CMR and to provide an initial external calibration.

Relationship of cloudiness to near surface temperature over land areas of the Northern Hemisphere for the past several decades is assessed using the data from surface meteorological weather stations, satellite observations, and the NCEP reanalysis project. The overall cloud relationship to near surface temperature is well represented by near surface humidity and surface conditions. Nighttime cloud-related surface warming decreases with the increase in near surface specific humidity. After cloud longwave-related temperature change and snow cover information are removed, one unit of cloud cover is empirically associated with a surface cooling of 0.59 K. The AMIP-1 models generally were able to reproduce the cold season cloud-temperature relationship, but not for the warm season and for the diurnal cycle. The daytime cloud-related surface cooling over China and the contiguous U.S. generally strengthened, but slightly weakened over Canada and the former USSR during the post WWII period. Since the 1970s a prominent increase in atmospheric humidity has weakened cloud longwave effect on surface temperature (best seen at nighttime) over the extratropical land areas. Significant changes and a general redistribution of cloudiness occurred over the contiguous U.S. and the former USSR (south of 60°N) during the past forty to fifty years. Low cloudiness increased over the contiguous U.S. while it decreased over the former USSR (south of 60°N) Total cloud amount and convective cloud frequency increased in both countries.

Two sympatric Phoebetria albatrosses, P. fusca and palpebrata breeding at Marion Island in the South Indian Ocean were studied. Adult individuals were tracked between 2008 and 2011. The study examined the foraging distribution of the two species in relation to environmental parameters such as sea surface temperature. Interaction with mesoscale features expressed by sea surface temperatures, was tested with statistical models. Tracked P. fusca demonstrated positive association with sea surface temperatures in the Southern Indian Ocean, in particular during incubating and chick-provisioning periods, by travelling shorter distances to the interfaces of mesocale features created as a result of the Agulhas Return Current located << 500 km to the north of breeding islands. During nest construction, tracked P. fusca travelled greater distances in search of food possibly because they had no chick to return to at the colonies. Contrastingly, tracked P. palpebrata did not demonstrate any positive association with sea surface temperatures. During incubating and chick-provisioning periods, tracked P. palpebrata travelled shorter distances to foraging grounds located to the south of breeding islands possibly to maximise returns to chicks while minimising efforts. During nest construction, tracked P. palpebrata travelled to distant foraging grounds to the south of the Antarctic Polar Front in areas of low mesoscale variability suggesting that greater distances can be achieved when they have no chick to feed at the colonies. Individuals of both tracked species foraged within close proximity during energy-demanding periods indicating their ability to employ an efficient foraging strategy that ensures minimal effort whilst maximising returns. Generalised Linear Models with the response variable being species and explanatory variables comprised of sea surface temperatures, annual breeding stages, distance traversed and activity, were conducted to examine the effect of environmental factors on seabird foraging distribution. These models were subjected to robust fitness tests and those that represented ecological reality of the two tracked albatrosses were chosen. The study demonstrates that the most important foraging areas for these two tracked seabird species overlap with the Indian Ocean Tuna Commission Convention area making them vulnerable from incidental capture from high longline fisheries. These results have implications to the conservation of these albatrosses suggesting a need for a multi-faceted approach on fisheries management particularly on mitigation of seabird bycatch in the Indian Ocean Tuna Convention area.

Ensemble calculations for the period from 2000 to 2010 were carried out with the middle and upper atmosphere model (MUAM), and an analysis of the quarterdiurnal tide is performed. The global temporal and latitudinal distributions of the quarterdiurnal tide are modeled with MUAM, and their forcing mechanisms are examined. The quarterdiurnal tides show a similar distribution over the year in the northern and southern hemisphere, with maxima of the amplitude in late winter and spring as well as in autumn. In the latitude-height distribution is also shown that the largest amplitudes of the quarterdiurnal tide are seen at midlatitudes. Due to the decreasing density with height, there is a general increase of the tidal amplitudes with height. The results of the forcing analyses show that direct solar forcing is most important, but also that non-linear forcing and gravity wave interaction with other tides have a non-negligible influence on the quarterdiurnal tide in the middle and upper atmosphere. / Mit dem Modell für die mittlere und obere Atmosphäre MUAM wurden Ensemble-Berechnungen für den Zeitraum 2000 bis 2010 durchgeführt und die vierteltägigen Gezeiten analysiert. Es wird auf die globale zeitliche und räumliche Verteilung der vierteltägigen Gezeiten eingegangen und deren Anregungsmechanismen untersucht. Die vierteltägigen Gezeiten zeigen einen ähnlichen Verlauf über das Jahr auf der Nord- und Südhalbkugel mit Maxima der Amplitude im späten Winter und Frühjahr sowie im Herbst. Ein ähnliches Bild zeigt sich auch für die Verteilung im Breiten-Höhen-Schnitt, wo die größten Amplituden der vierteltätigen Gezeiten in den mittleren Breiten zu finden sind. Aufgrund der abnehmenden Dichte mit der Höhe ist eine allgemeine Zunahme der Amplituden mit der Höhe zu beobachten. Es zeigte sich, dass der direkte solare Antrieb am stärksten ausgeprägt ist, aber auch, dass der nichtlinearer Antrieb und die Interaktion von Schwerewellen mit anderen Gezeiten einen nicht zu vernachlässigenden Einfluss auf die vierteltägigen Gezeiten in der mittleren und oberen Atmosphäre haben.

Marine surface layer micrometeorology mainly constitutes vertical turbulent fluxes of parameters such as momentum, heat, water vapour and aerosols. These turbulent fluxes have been tested in the laboratory and can be applied to the atmospheric changes over the ocean, where wind speed, the air-sea temperature difference (ASTD) and humidity play a major role. Due to the difficulty of actually measuring these changes directly, equations were derived that describe the micrometeorology in terms of actual meteorological observations. The theory of micrometeorology in turn provided the accepted calculations to predict vertical profiles for wind speed, air temperature and humidity. Nevertheless, using micrometeorology theory to predict atmospheric conditions over the ocean proves to be more difficult than over land. This is mainly due to the complex nature of the oceanic environment and its interaction with the atmosphere directly above it. The primary objective of this work was therefore to investigate the potential of deploying a Helikite in order to characterise the lower atmosphere in False Bay. Focus was placed on the methods to correctly measure air profiles over the ocean up to a maximum height of 200 m. A description of the system set-up, data acquisition, deployment parameters and data analysis are discussed. The second objective was to evaluate the micrometeorology theory used in a micrometeorological model for the marine surface layer with False Bay data. This was achieved by using experimental data to run the model. The model output was then compared to the experimental profile measured as part of objective one. The micrometeorological model it aimed to assess is based on the standard bulk meteorological observations of wind speed, temperature, humidity and the turbulent fluxes of momentum, heat and water vapour. Analysis of the various environmental parameters showed a complex oceanographic and atmospheric system. The air profiles recorded for this study were recorded in an area where smaller scale local effects were dominant, which could explain some of the discrepancies encountered when attempting to reproduce the measured profiles using micrometeorology bulk parameterisations. The four profiles described in this thesis were grouped with two profile days showing a good comparison between the predicted and measured profiles. Results also indicated that micrometeorology theory perform better when using the ‘bucket’ Sea Surface Temperature (SST) at 0.5 m below the surface.

This work examines intra-seasonal rainfall variability over the summer rainfall region of South Africa. Spectral analysis of a precipitation minus evaporation index (P-E) compiled from 16 rainfall stations in the western Transvaal region of South Africa has shown that two dominant spectral peaks occur in the water budget or convection as identified by an outgoing longwave radiation (OLR) index and P-E index. A longer 40-60 day oscillation or Madden Julian Oscillation (MJO) and a shorter 20-30 day ISO are identified. The interaction between the Rossby waves of the mid-latitudes and the MJO of tropics appears to be the main cause of the 20-30 day ISO operating over southern Africa. Hovmoller analysis at 10° S and 40° S has shown that four modes exist in the propagation and oscillatory characteristics of various anomalies. Eastward and westward propagation is noted as well as standing wave patterns and "flip-flop" modes where anomalies alternate between positive and negative across the latitude band with time. The composite analysis revealed a tropically initiated signal of the 20-30 day ISO in the water vapour flux (WVF) anomaly field where strong easterly WVF vectors are noted between the equator and 10°S and between 40° E and 80° E. Strong convergence of water vapour occurs during the wet phase of the 20-30 day ISO over the south-western Indian Ocean and together with strong ridging of the South Atlantic Anticyclone (SAA) causes the south-easterly advection of moisture from the southern Mozambique Channel and over the warm Agulhas Current into South Africa. Post-wet phase anomaly composites do not show much similarity with pre-cursor anomaly composites. This implies that the 20-30 day ISO may be a half cycle of 40-60 days which is consistent with the MJO. However, it is felt that 20-30 day ISO's affecting the southern African region alternate in intensity within the period of the MJO.