In this thesis, we introduce a new approach to classify rain clouds based on the relationship between the emission signal and scattering signal derived from microwave brightness temperature data. Two parameters are used as indicators of emission signal and scattering signal respectively: one is the polarization difference (D) at 19 GHz, and the other one is the polarization-corrected temperature (PCT) at high-frequencies channels. D is related to the emission of liquid hydrometeors, and PCT mainly reflects the brightness temperature depression due to the scattering by ice particles. Both D and PCT decrease with increasing precipitation rate. Therefore, certain combinations of D and PCT can be regarded as the representatives of cloud hydrometeor structures. Based on the D-PCT relationship investigated in this study, we classified the observed rain clouds into five categories—non-precipitating, light-precipitating, liquid-dominant precipitating, well-mixed precipitating, and ice-dominant precipitating clouds. We verified the results of the classification of different precipitation cases over tropical regions. For both the hurricane and front cases, the results show that the distributions of categorized cloud pixels can reflect the horizontal structure of the weather systems. The monthly gridded mean frequencies of categorized precipitating clouds are used to analyze the relationship between the seasonal and interannual cycles of tropical precipitation and clouds’ hydrometeor components. Moreover, the results indicated that in an annual cycle or an ENSO cycle, when the local precipitation frequencies increase, the occurrence frequencies of all kinds of rain clouds will increase. However, among those precipitating systems, the proportions of ice-dominant and well-mixed clouds increases while that of water-dominant clouds decrease as the local precipitation increases. Anomalies of the opposite sign tend to accompany the decreasing precipitations situations. Overall, the classification method proves to be useful to extract objective information from observed emission and scattering signals. Since clouds have always been signs of the weather systems, the long-term variances of global distribution and characteristics of rain clouds are as an aspect of cloud climatology. Moreover, the categorization of precipitation types can be useful in developing the best retrieval algorithm of rain rate for a specific cloud type. Additionally, the information about cloud types can be used to improve our understanding of cloud processes and to increase the accuracy of weather and climate models. / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester 2019. / March 5, 2019. / Classification, Emission, Microwave, Rain clouds, Scattering / Includes bibliographical references. / Guosheng Liu, Professor Directing Thesis; Vasubandhu Misra, Committee Member; Allison Wing, Committee Member.

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Graduation date: 1981

Two successive years of wind speed and direction data, from January 1973 through December 1974, have been measured and recorded at Yaquina Head, 6 km north of Newport, Oregon. Analysis of the data permitted 65 cases of strong wind to be isolated and separated into four distinct wind speed categories. With the aid of surface charts, upper air sounding, and sea level pressures from several stations, numerous meteorological events, occurring concurrently with peak winds at Yaquina Head, have been evaluated for a significant contribution to the local wind. Cyclone centers associated with strong coastal wind have been plotted and analyzed with regard to location, speed and direction of motion, sea surface pressure, and pressure change during periods of strong winds. The result of this analysis indicates that many cases of strong coastal wind measured at Yaquina Head are associated with cyclones located southwest of Vancouver Island, British Columbia. The pressure change experienced by these cyclones is related to the strength of the observed wind at Yaquina Head. Likewise, the locations of these pressure centers are related to the duration of strong wind measured at Yaquina Head. The direction of motion of the cyclones and the value of the sea surface pressure at the center of the cyclones seem unrelated to local wind speed. Frontal zones associated with cases of strong wind have been evaluated with regard to type, speed, and direction of motion prior to strong surface winds. No relationship was found between these factors and the strength of the wind. The direction of the wind versus the speed of the wind was reviewed and the results were separated into several classes. The result of this classification indicated that in 73 percent of the cases the measured peak wind occurred prior to an abrupt veering of the wind. Only 21 percent of the cases lacked this wind shift. The local pressure field was examined for pressure differences which might result in a strong coastal wind flow. Station pressures from three locations were used as well as barograms from Newport, Oregon, in describing the pressure field. No correlation between these pressures differences and the strength of the local wind could be found. Finally, the north-south component of the geostrophic wind was calculated and compared with speed of the measured wind. No consistent agreement could be established between the measured surface wind speed and the calculated north- south component of the geostrophic wind. The lack of data west of Yaquina Head and Oregon Coast continue to present a problem for those who consider coastal winds. / Graduation date: 1977

The dynamical processes which maintain atmospheric disturbances in regions of strong wintertime variability of the northern hemisphere are examined using data from a GCM simulation. Time series of the dependent variables and diabatic heating components from 10 Northern Hemisphere winters simulated by the Oregon State University two-level GCM are used. Variance and covariance analyses are performed to determine the geographical distribution of the intensities and transport properties of high-frequency (periods between 2.5 and 10 days) and low-frequency (periods between 10 days and a season) eddies. These are compared with existing observations and the discrepancies are discussed in terms of their dynamical consistency with the time-mean circulation. The energetics of high-frequency and low-frequency eddies are studied. It is found that the behavior of high-frequency eddies is consistent with baroclinic instability theory. Low-frequency eddies appear to be maintained mainly by a high-latitude baroclinic energy cycle. Energy conversions characteristic of barotropic processes are also significant at jet-stream-latitudes. The process of wave-energy dispersion is found to be an important factor governing the geographical distribution of low-frequency activity at middle latitudes. The nature of the systems causing low-frequency variability over the North Pacific Ocean is examined by applying complex EOF analysis to the time series of geopotential height anomalies. The first eigenmode of this analysis describes a wave of planetary scale extending from northeastern Asia to the Gulf of Mexico across the North Pacific basin. While the phase of this wave retrogrades along the continental borders of the ocean basin, energy propagates in the opposite direction and penetrates as far as the central North Atlantic. The dynamical characteristics of this disturbance are examined by complex covariance analysis between the first mode's principal component and the dependent-variable fields. It is found that the disturbance grows mainly through baroclinic processes with some contribution from barotropic processes. On the basis of these results it is proposed that the observed differences between the high- and low-frequency disturbances result from their being generated in different geographical regions where sphericity and the properties of the stationary flow cause baroclinic growth of structurally different modes. / Graduation date: 1985

Globally intermittent turbulence is characterized by sudden switching from significant turbulence to weak turbulence and back on time scales ranging from seconds to tens of minutes as opposed to microscale intermittency, which is due to organization of small scale gradients by individual eddies on scales as small as the Kolmogorov microscale. This thesis examines globally intermittent turbulent atmospheric data by a conditional analysis technique. The conditional analysis separates the stronger turbulence sections of data from the weak sections and analyzes each type separately. This analysis is applied to two different sources of global intermittency. One case arises from the undulating structure of the top of a convective internal boundary layer that was forming due to a cool marine boundary layer being modified by a sun-heated beach. The other case is nocturnal boundary layer intermittency, the causes of which are not well known. When applied to the top of the convective internal boundary layer, the conditional analysis performs well in that a turbulent kinetic energy budget can be balanced. Conventional analysis of the same data is unsatisfactory. The conditional analysis improves the behavior of relationships for nocturnal intermittency, especially in that it reduces non-stationarity, but it does not explain all the scatter in the data. This may be due to the large role of self-correlation in the traditional presentation of the data. / Graduation date: 2003