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Browsing by Author "Demuth, Julie L., author"

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    Developing a valid scale of past tornado experiences
    (Colorado State University. Libraries, 2015) Demuth, Julie L., author; Trumbo, Craig, advisor; Long, Marilee, committee member; Morss, Rebecca, committee member; Most, David, committee member; Peek, Lori, committee member; Zimmerman, Donald, committee member
    People's past experience with a hazard theoretically is a key factor in how they perceive a future risk because experience is a mechanism through which one acquires knowledge about a risk. Despite this, past hazard experience has been conceptualized and measured in wide-ranging and often simplistic ways by researchers, resulting in mixed findings about the relationship between experience and risk perception. Thus, dimensions of past hazard experiences are not validly known, nor is it known how one's experiences relate to their assessment of future risks. Past hazard experience is particularly relevant in the context of weather risks, which are common enough for people to acquire many experiences. This dissertation presents the results of a study to develop a valid scale of past experiences in the context of tornado risks. The scale is developed by, first, conceptualizing and identifying dimensions of past tornado experience, and subsequently by examining the relationship between the different experience dimensions and people's tornado risk perception. Data were collected through two mixed-mode (Web+mail) surveys of the public who reside in tornado-prone areas. An initial set of items to measure people's most memorable tornado experience as well as their experiences with multiple tornado threats were developed and evaluated with the first survey. Additional aspects of people's past tornado experiences were elicited in their own words to identify potentially important ideas that were not captured in the original item set. The item set then was revised and evaluated with the second survey. The second survey also included a scale to measure people's cognitive-affective tornado risk perceptions. Six latent dimensions of people's past tornado experiences emerged from this study: most-memorable experience-related risk awareness, risk personalization, personal intrusive impacts, and vicarious troubling impacts, as well as multiple experiences with common personal threats and impacts and negative emotional responses. Risk awareness captures the event-specific awareness by the respondent and from social cues about the possibility of the hazard occurring and concern about it causing harm. Risk personalization captures one's protective and emotional responses as well as direct visual, auditory, and tactile sensory inputs of the hazard. Personal intrusive impacts capture unwelcome thoughts, feelings, and disruption caused by the hazard. Vicarious troubling impacts capture the tangible property damage and loss incurred by others, disruption to others, and others' verbal accounts of their experiences. Common personal threats and impacts capture the amount of experiences one has with official tornado warnings and sirens and with news coverage about tornado events and their impacts. Finally, negative emotional responses capture the amount of experience one has fearing and worrying due to tornadoes. Subsequently, these different dimensions were shown to have varying influences on cognitive, affective, and overall tornado risk perception. Personal intrusive impacts had a pervasive effect, enhancing each of the risk perception dimensions with especially strong influences on affective and overall risk perception. Risk awareness and risk personalization influenced cognitive and overall risk perception, but only when combined with the other experience dimensions, suggesting that these experiences may be made more salient when joint with others. Overall, this research theoretically advances how past experience is conceptualized and how it relates to risk perception, and it serves as a foundation for future theoretical and applied research that could leverage and extend this work.
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    ItemOpen Access
    Objectively estimating tropical cyclone intensity and wind structure using the advanced microwave sounding unit
    (Colorado State University. Libraries, 2001) Demuth, Julie L., author; Vonder Haar, Thomas H., author; Cooperative Institute for Research in the Atmosphere (Fort Collins, Colo.), publisher
    Estimating tropical cyclone (TC) intensity and structure is becoming increasingly important in light of population expansion along coastal regions. The two most commonly used techniques for estimating TC intensity, the Dvorak Technique and the Objective Dvorak Technique (ODT), utilize visible and infrared satellite imagery. However, both have limitations, as do observing techniques of TC wind structure. Satellite-borne passive microwave radiometers provide an opportune alternative for near real-time assessments of TC maximum sustained winds and wind radii. The first Advanced Microwave Sounding Unit (AMSU), aboard the NOAA-15 polar orbiting satellite, is the first NOAA instrument with sufficient resolution to do so. In this study, data derived from AMSU temperature, pressure, and wind retrievals are used to make objective intensity and wind radii estimates for tropical disturbances in the Atlantic and East Pacific basins. To approximate TC maximum sustained winds and azimuthally averaged wind radii of 34, 50, and 64 kt winds, algorithms are developed via correlations and multiple linear regressions from AMSU data from the 1999 tropical season; they then are tested independently on the 2000 tropical season data Additionally, the AMSU-derived estimates of the azimuthally averaged wind radii are used with a modified Rankine vortex model to assess the wind radii asymmetrically, specifically in the northeast (NE), northwest (NW), southeast (SE), and southwest (SW) quadrants of the TC. Validation data are from the National Hurricane Center (NHC) best track data for the intensity estimates, and from the NHC operational forecast advisories for the average and asymmetric wind radii estimates. Results show the objective AMSU algorithm is comparable to the ODT for estimating TC intensity in the Atlantic, with a root mean square error (RMSE) of 13 kts. The RMSE increases slightly to 16 kts for both basins combined. In general, the AMSU algorithm has a tendency to over (under) approximate the intensity of weak (strong) TCs. For the AMSU-estimated azimuthally averaged 34, 50, and 64 kt wind radii, the mean absolute errors (MAE) are 16, 17, and 8 nautical miles (nm), respectively. With respect to the average radii of each, these correspond to errors of 14.4 percent, 24.6 percent, and 17.8 percent. As with the intensity estimation algorithm, there is a tendency toward over (under) estimation of small (large) azimuthally averaged wind radii by the AMSU. Additionally, the wind radii estimates in the NE, SE, SW, and NW quadrants capture the asymmetric structure well, generally comparing favorably with the NHC operational advisory estimates. In some cases, the AMSU estimates may even be superior to NHC estimates, especially in the Eastern Pacific. Finally, the 1999 and 2000 AMSU data are combined to refine the TC intensity and azimuthally averaged wind radii estimation algorithms. The two-year based algorithms currently are being tested on AMSU data received from the Atlantic and East Pacific basins during the 2001 tropical season.