ABSTRACT The relationships between high ozone events and synoptic weather patterns were investigated based on the meteorological and air-quality data at four monitoring stations in Kaohsiung city during 1997 to 2004 in this study. The PCA (principal component analysis) and correlation studies show that ozone concentration exhibit positive correlations with the ambient temperature and sunshine duration, while negative correlation with the cloud cover. The frequency of high ozone events was highest under the weather patterns of northeast seasonal wind (B1 type), high-pressure system with recirculation (B3 type), high-pressure system with offshore type (B2 type), and in the warm core of approaching front (B4 type), most frequently in autumn, winter, and spring, and least frequently in summer. The above four weather patterns are primarily dominated by the high-pressure system from Mainland China, with relatively cold and dry weather and little rain in Taiwan. Since the high-pressure center is usually located north or northeast of Taiwan during autumn, winter, and spring such that the leeside areas of Central Mountain Ranges in the western coast of Taiwan are prone to high pollution events, particularly when the wind speed is low (< 4m/s) and duration of sunshine is long (> 5.5 hr). Or sometimes the meso-scale wind system, for example, the sea-land breeze or the combined flow caused by the detouring flow from the Henchun Peninsula and northeast wind tends to raise the pollutant concentrations. Keywords¡GHigh ozone event, Synoptic weather pattern, Principal component analysis.

Abstract This study aims to investigate the influence of micrometeorology on atmospheric visibility in Taipei Basin by carrying on routine and intensive visibility observation, analyzing particle concentrations and size distribution, monitoring atmospheric optical coefficients of particles, and collecting meteorological conditions (wind direction, wind speed, temperature and humidity). Based on the information of the broad view of the meteorological parameters from 1998 to 2005, the air pollution episode in Taipei Basin mainly occurred during the winter periods accompanied with the weather patterns of high pressure outflow style I, high pressure outflow style II or circus-sluice of high pressure outflow. Based on the collected visibility data from Taipei of Central Weather Bureau for the past 21 years (1983~2004), it shows the visibility increasing each year. The visibility seasonal variation was also observed higher than that during winter. The mean visibilities from Tamsui, Songshan, and Sindian directions are 10.54 km , 9.72 km and 8.62 km, respectively. In general, the visibility from the Tamsui direction is slightly higher than those the from two directions, This result shows visibility is influenced not only the pollution factor and meteorological factor, but affected by the local topography. Our study revealed that the visibility data leads on the Tamsui, Songshan obserrative directions is better. Two intensive sampling campaign were conducted during August 15~22 of 2004 and January 15~22 of 2005 on the roof of Taipei County Government, respectively. The results showed mass concentration of particulate matter in winter is higher than that in summer. A bi-mode size distribution of aerosol particles was also observed in the Taipei basin. Two peaks of aerodynamic diameter of PM were observed at 0.56~1.0 &#x00B5;m and 3.2~5.6 &#x00B5;m, respectively. In addition, extinction coefficient is always high during winter. Mean scattering coefficient is about 80~108 Mm-1 while the mean absorption coefficient is around 9~35 Mm-1, during the 1st intensive sampling period. Mean scattering coefficient is about 101~119 Mm-1 while the mean absorption coefficient is around 16~64 Mm-1, during the 2nd intensive sampling period. Our study also shows that visibility has a higher correlation with fine particles(R=0.70~0.96) than that with coarse particles(R=0.045~0.629). Hance, visibility is affected mainly by fine particles. In general, the intensive observation of visibility also shows that in summer the visibility is higher than that in winter. In addition, the analysis from MM5 shows that the visibility for the Tamsui direction is usually influenced by the prevailing wine direction, It is because of that northwestern from sea brings lots of water spray into the basin. This spray water will increase the particle diameter and cause the increasing of extinction coefficient. It will also impair the visibility.

Spatial variability of rainfall is a significant factor in hydrologic and water quality modeling. In recent years, characterizing and analyzing the effect of spatial variability of rainfall in hydrologic applications has become vital with the advent of remotely sensed precipitation estimates that have high spatial resolution. In this study, the effect of spatial variability of rainfall in hourly runoff generation was analyzed using the Soil and Water Assessment Tool (SWAT) for Big Sandy Creek and Walnut Creek Watersheds in North Central Texas. The area of the study catchments was 808 km2 and 196 km2 for Big Sandy Creek and Walnut Creek Watersheds respectively. Hourly rainfall measurements obtained from raingauges and weather radars were used to estimate runoff for the years 1999 to 2003. Results from the study indicated that generated runoff from SWAT showed enormous volume bias when compared against observed runoff. The magnitude of bias increased as the area of the watershed increased and the spatial variability of rainfall diminished. Regardless of high spatial variability, rainfall estimates from weather radars resulted in increased volume of simulated runoff. Therefore, weather radar estimates were corrected for various systematic, range-dependent biases using three different interpolation methods: Inverse Distance Weighting (IDW), Spline, and Thiessen polygon. Runoff simulated using these bias adjusted radar rainfall estimates showed less volume bias compared to simulations using uncorrected radar rainfall. In addition to spatial variability of rainfall, SWAT model structures, such as overland flow, groundwater flow routing, and hourly evapotranspiration distribution, played vital roles in the accuracy of simulated runoff.

A comparison of flash parameters from the National Lightning Detection Network (NLDN) is made with data obtained from the Houston Lightning Detection and Ranging II (LDAR) network. This research focuses on relating the peak current and number of strokes in a negative flash (multiplicity) of lightning with the spatial extent and mean altitude of three-dimensional lightning in 1407 flashes as mapped by the LDAR network. It is shown that increasing negative multiplicities over the range two through ten exhibit, on average, a higher flash extent with higher multiplicities. Singlestroke flashes have mean heights of nearly 2 km greater. Higher order multiplicities (2 to 10+) were correlated with mean source heights near 8 km. Increasing multiplicity tends to be associated with greater flash extents increasing more horizontally than vertically with a 50% to 70% increase in flash extent. No obvious relationship between peak current and flash extent was observed. Examining peak current and mean height shows that low current flashes (<10kA) exhibit higher mean heights. However, this may be due to intra-cloud only flashes being reported as cloud to ground events by the NLDN. Bipolar flashes do not show much variation with height and flash extent with the exception of negative-first bipolar flashes, which exhibited mean flash extents twice that of other types. Finally, the flash detection efficiency is 99.7% within 60 km of the network center.

Cold air outbreaks (CAOs) occur when large scale atmospheric circulations allow for the incursion of polar air masses into middle and lower latitudes, influencing wintertime temperatures regionally. The January 2004 CAO is identified as a major CAO in the Deep South of the United States in terms of wind chill equivalent temperature or a temperature-only criterion. Surface air temperature, horizontal winds, specific humidity, and Ertel potential vorticity are analyzed for this event using several reanalysis products: National Aeronautic and Space Administration Modern Era Retrospective-Analysis for Research and Application (MERRA), the National Centers for Environmental Prediction National Center for Atmospheric Research (NCEP-NCAR), and the National Centers for Environmental Prediction North American Regional Reanalysis (NARR). We perform an intercomparison of the reanalysis products and parallel surface station observations during the synoptic evolution of the leading cold front associated with CAO onset. The key synoptic, mesoscale, and dynamical features associated with onset are studied to determine the relative accuracy of the respective reanalysis products in representing the key features. The comparative evaluation revealed pronounced temperature and moisture biases in the NCEP-NCAR reanalysis products that limit its utility in portraying the synoptic features characteristic of CAO onset. Conversely, both MERRA and NARR accurately represent the detailed thermodynamic and moisture structural evolution associated with CAO onset indicating their utility in future observationally-based studies of CAO events. Ertel potential vorticity analyses indicate that the onset of the 2004 CAO is strongly linked to an incipient tropopause fold feature that developed over the Great Lakes region.

Honeywell Technology Solutions Lab, India / Weather is a major contributing factor in aviation accidents, incidents and delays. Doppler weather radar has emerged as a potent tool to observe weather. Aircraft carry onboard radars but their range and angular resolution are limited. Networks of ground-based weather radars provide extensive coverage of weather over large geographic regions. It would be helpful if these data can be transmitted to the pilot. However, these data are highly voluminous and the bandwidth of the ground-air communication links is limited and expensive. Hence, these data have to be compressed to an extent where they are suitable for transmission over low-bandwidth links. Several methods have been developed to compress pictorial data. General-purpose schemes do not take into account the nature of data and hence do not yield high compression ratios. A scheme for extreme compression of weather radar data is developed in this thesis that does not significantly degrade the meteorological information contained in these data. The method is based on contour encoding. It approximates a contour by a set of systematically chosen ‘control points’ that preserve its fine structure up to a certain level. The contours may be obtained using a thresholding process based on NWS or custom reflectivity levels. This process may result in region and hole contours, enclosing `high' or `low' areas, which may be nested. A tag bit is used to label region and hole contours. The control point extraction method first obtains a smoothed reference contour by averaging the original contour. Then the points on the original contour with maximum deviation from the smoothed contour between the crossings of these contours are identified and are designated as control points. Additional control points are added midway between the control point and the crossing points on either side of it, if the length of the segment between the crossing points exceeds a certain length. The control points, referenced with respect to the top-left corner of each contour for compact quantification, are transmitted to the receiving end. The contour is retrieved from the control points at the receiving end using spline interpolation. The region and hole contours are identified using the tag bit. The pixels between the region and hole contours at a given threshold level are filled using the color corresponding to it. This method is repeated till all the contours for a given threshold level are exhausted, and the process is carried out for all other thresholds, thereby resulting in a composite picture of the reconstructed field. Extensive studies have been conducted by using metrics such as compression ratio, fidelity of reconstruction and visual perception. In particular the effect of the smoothing factor, the choice of the degree of spline interpolation and the choice of thresholds are studied. It has been shown that a smoothing percentage of about 10% is optimal for most data. A degree 2 of spline interpolation is found to be best suited for smooth contour reconstruction. Augmenting NWS thresholds has resulted in improved visual perception, but at the expense of a decrease in the compression ratio. Two enhancements to the basic method that include adjustments to the control points to achieve better reconstruction and bit manipulations on the control points to obtain higher compression are proposed. The spline interpolation inherently tends to move the reconstructed contour away from the control points. This has been somewhat compensated by stretching the control points away from the smoothed reference contour. The amount and direction of stretch are optimized with respect to actual data fields to yield better reconstruction. In the bit manipulation study, the effects of discarding the least significant bits of the control point addresses are analyzed in detail. Simple bit truncation introduces a bias in the contour description and reconstruction, which is removed to a great extent by employing a bias compensation mechanism. The results obtained are compared with other methods devised for encoding weather radar contours.

Für die zukünftige klimatische Entwicklung in Mitteldeutschland wurden die Ergebnisse von zwölf globalen Klimamodellen ausgewertet. Im Laufe des 21. Jahrhunderts ergeben sich aus den untersuchten Simulationen für alle Jahreszeiten Temperaturzunahmen. Die Zunahmen der Jahresmitteltemperaturen bewegen sich je nach Modell und Emissionsszenario zwischen 0,5 K und 4,8 K. Während die Zunahmen im Frühjahr vergleichsweise moderat ausfallen, unterliegen die (Spät)sommer und Wintermonate einem besonders starken Erwärmungstrend. Hinsichtlich der Niederschlagsentwicklung ergeben sich insbesondere in den Sommermonaten signifikante Abnahmetrends. Besonders betroffen sind hierbei die Monate Juli und August. Deutlich zunehmende Winterniederschläge führen zu nur vergleichsweise unauffälligen Veränderungen der Jahresniederschlagssummen (Niederschlagsumverteilung). Insbesondere die kombinierte Wirkung von erhöhten Temperaturen und deutlich abnehmenden Niederschlägen sowie der damit einhergehende erhöhte Verdunstungsanspruch während der Sommermonate birgt die Gefahr angespannter Wasserhaushaltssituationen.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Geography." Includes bibliographical references (p. 107-124).

Thesis (M.S.)--University of Utah, 2000. / "FY00-246." Title from web page (viewed Nov. 13, 2003). Includes bibliographical references (p. [118]-122). Also available in print version.

published_or_final_version / Statistics and Actuarial Science / Doctoral / Doctor of Philosophy