Thesis (Ph. D.)--University of Oklahoma, 1993. / Includes bibliographical references (leaves 189-195).

Thesis (M. Phil.)--University of Hong Kong, 1976.

Based upon the author's doctoral dissertation, University of California, Los Angeles, 1972. / "UCAL-WRC-W-254." Includes bibliographical references (p. 81-99).

Cypress Mountain, north of Vancouver, is a coastal barrier for moisture-laden onshore airflow and subject to large amounts of precipitation. The athletic events at this site during the 2010 Winter Olympics were frequently delayed due to the occurrence of rain rather than snow. Unprecedented data on precipitating systems were obtained between January and April 2010 during the SNOW-V10 (Science and Nowcasting Olympic Weather for Vancouver 2010) field campaign. This included information collected from specialized radar, enhanced surface weather stations, as well as from operational radar and satellite data. Some precipitation events lasted ≥ 24 h, although heavier precipitation rates typically lasted ≤ 6 h. Freezing rain was also inferred. Specialized radar showed changes in reflectivity values with height, yielded information regarding melting layer heights, and detected upward motion of precipitation particles. Differences in daily precipitation amounts of ≥ 50 mm from on the mountain to its base were also measured. / October 2015

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisors: Brian Hanson and David R. Legates, Dept. of Geography. Includes bibliographical references.

Forecasts of the likelihood of occurrence of various amounts of precipitation are very important, since excessive precipitation amounts over relatively short time periods can have adverse effects on public safety and economic efficiency, As a result, forecasters at the National Weather Service Forecast Office in San Antonio, Texas were asked to formulate subjective probabilistic quantitative precipitation forecasts on an experimental basis beginning in February 1981. This study describes methods of evaluating probability forecasts of this ordinal variable and presents some results of the first year of the experiment. Scalar and vector evaluation procedures are described. In the case of scalar evaluation, the inclusion of a no-skill line and a no-correlation line on reliability diagrams is helpful in representing the skill, reliability, and resolution qeometrically in two-state situations. Geometrical interpretations of attributes of forecasts can also be accomplished in three-state situations based on vector evaluation procedures. A skill score for subsample forecasts is shown to be useful in identifying systematic errors made by forecasters or forecast systems. A beta model is developed to obtain a forecaster's predictive distributions (i.e., the distribution of use of probability values). The experimental results show that the skill of the subjective forecasts is generally higher than the skill of objective guidance forecasts for measurable precipitation (i.e., precipitation amounts exceeding a threshold of 0.01 inches), but that the opposite is true for threshold associated with larger precipitation amounts. This result is due primarily to the forecaster's tendency to over forecast for the events associated with higher precipitation thresholds. The tendency to over forecast is most pronounced in the nighttime forecasts and in the forecasts for drier stations. The MCS objective guidance forecasts, on the other hand, are quite reliable for both periods and all stations. The vector evaluation approach indicates that the degree of overforecasting is quite high for bimodal forecasts and that the skill contribution from bimodal forecasts is negative in many cases. / Graduation date: 1983

Due to the effects urbanization has on land-use and land cover change (LULC), urban areas have a major influence on the environment. The strong coupling between the land and atmosphere can alter the microclimatology of cities and their surrounding regions. Previous research has shown that cities can influence regional precipitation patterns. This is a result of many factors such as: increased heating and lifting caused by the urban heat island effect (UHI), increased pollution and aerosols, alteration of land use/land cover (which includes surface albedo, presence or lack of vegetation, and surface roughness changes), and urban design (which leads to increased friction and convergence). This study analyzes temporal and regional changes in the precipitation patterns of the Dallas/Fort Worth Metroplex as it has grown over the past century, and provides a methodology for testing urban influences on precipitation in other metropolitan areas. Precipitation from 1930 – 2007 was analyzed for the following three study regions: DFW (urban area), CRA (upwind control region), and CRB (downwind control region). By comparing early (1930 – 1950) and late period (1987 – 2007) precipitation within each region, it was found that there were no statistically significant differences between the two periods. Entire period precipitation (1930 – 2007) at CRB was statistically significantly different from both DFW and CRA although early and late period precipitation was not. While precipitation was similar between the two periods in all regions, comparing precipitation between the regions using the entire period shows potential anthropogenic influences. Land cover change between 1976 and 2001 was analyzed and it was found that water in the DFW Metroplex study region increased by 54.75%, vegetation decreased by 20.34%, and urban land cover increased by 176.14%. This may increase atmospheric moisture, surface temperature, friction and lifting over the urban center, and decrease the amount of heat released from the ground. While natural climate variability is the most important factor influencing precipitation in this region, it is possible that urbanization is also changing local and regional precipitation patterns, it may not be the only factor influencing change.

Trends in precipitation and extreme occurrence were analyzed for five locations across Canada using the Canadian Regional Climate Model. Results from the model’s base simulation were compared to those from a future scenario of increased atmospheric CO2. The climatology of nearby weather stations was used to assess the model’s ability to simulate the present and future climate. Other parameters such as 850 and 500 hPa geopotential associated with the most extreme events were analyzed to infer changes in the mechanisms causing such events. The model underestimates annual precipitation along with extreme occurrence and intensity. A wetter, but more variable climate is projected for most locations. Frequency and intensity of extreme events increases at most locations. Simulated extreme events over western locations were found to be associated with cold lows, while eastern events were linked with moisture transport at 850 hPa. Western events were reproduced accurately, whereas eastern ones were not.

Trends in precipitation and extreme occurrence were analyzed for five locations across Canada using the Canadian Regional Climate Model. Results from the model’s base simulation were compared to those from a future scenario of increased atmospheric CO2. The climatology of nearby weather stations was used to assess the model’s ability to simulate the present and future climate. Other parameters such as 850 and 500 hPa geopotential associated with the most extreme events were analyzed to infer changes in the mechanisms causing such events. The model underestimates annual precipitation along with extreme occurrence and intensity. A wetter, but more variable climate is projected for most locations. Frequency and intensity of extreme events increases at most locations. Simulated extreme events over western locations were found to be associated with cold lows, while eastern events were linked with moisture transport at 850 hPa. Western events were reproduced accurately, whereas eastern ones were not.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 122-123). Also available via the Internet.