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Oceanography and Atmospheric Sciences and Meteorology

Theses and Dissertations

2001

Articles 1 - 12 of 12

Full-Text Articles in Physical Sciences and Mathematics

Evolution Of Cloud-To-Ground Lightning Discharges In Tornadic Thunderstorms, Wendy L. Seaman Mar 2001

Evolution Of Cloud-To-Ground Lightning Discharges In Tornadic Thunderstorms, Wendy L. Seaman

Theses and Dissertations

Air Force operations are directly impacted by weather on a daily basis. Erroneous forecasts negatively impact mission readiness and consequently cost the government time, in terms of wasted man-hours, and money. Advanced forecast lead-time could make a difference to minimize loss to both USAF personnel and assets. This study examined lightning data from 64 storm events from 1995-2000 in search of unique lightning signatures indicative of tornadic activity. Overall flash rates, percentage of positive flashes, positive and negative peak currents and multiplicity for each case were separated into two categories based on tornado intensity and season of occurrence. Based on …

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Validation And Characterization Of Ionospheric Densities Measured By Dmsp, Herbert L. Keyser Mar 2001

Validation And Characterization Of Ionospheric Densities Measured By Dmsp, Herbert L. Keyser

Theses and Dissertations

Future models of the thermosphere-ionosphere-magnetosphere system will require near real-time assimilation of ionospheric parameters to specify% and forecast these regions One of the current sensors that will be used in the GAIM model is the DMSP SSIES. Knowledge of the SSIES's reliability and data characteristics is key to using the data when relying on automated processes to ingest the data. To validate the DMSP value, the DMSP-measured density is compared to ground-based ISR measurements from solar minimum to solar maximum. The DMSP data are compared to data from the ISRs located at the Millstone Hill Observatory in Massachusetts and Sondrestrom …

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Development Of Predictors For Cloud-To-Ground Lightning Activity Using Atmospheric Stability Indices, Kenneth C. Venzke Mar 2001

Development Of Predictors For Cloud-To-Ground Lightning Activity Using Atmospheric Stability Indices, Kenneth C. Venzke

Theses and Dissertations

A detailed examination was performed on several commonly applied atmospheric stability indices and lightning activity from 1993 to 2000 to determine the indices usefulness as predictive tools for determining cloud-to-ground lightning activity. Predetermined radii of 50 nautical miles around upper-air stations in the Midwest U.S. were used for the lightning summaries. Also explored is an improvement upon the commonly accepted thresholds of the stability indices as general thunderstorm indicators. An improvement was found and new threshold ranges were developed for relating stability index values to lightning occurrence. Traditional statistical regression methods failed to find a significant predictive relationship. By examining …

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Atmospheric Conditions Associated With Lightning During Snow And Ice Events, Randall J. Haeberle Mar 2001

Atmospheric Conditions Associated With Lightning During Snow And Ice Events, Randall J. Haeberle

Theses and Dissertations

The purpose of this research was to find the atmospheric mechanisms associated with lightning in snow and ice events. The specific mechanisms that were examined were low-level wind shear, upper level divergence, surface temperature, low-level temperature, the -10 ° C level, and precipitable water. A chi-squared dependency test showed the strong association of low-level wind shear to each precipitation type (snow, sleet/freezing rain, rain) in two separate studies. Surface temperature appeared to have a relationship to lightning in all precipitation categories, while no significant relationship to lightning in all precipitation categories, while no significant relationship was found with upper level …

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Simulating Wet Deposition Of Radiocesium From The Chernobyl Accident, Aaron M. Kinser Mar 2001

Simulating Wet Deposition Of Radiocesium From The Chernobyl Accident, Aaron M. Kinser

Theses and Dissertations

In response to the Chernobyl nuclear power plant accident of 1986, a cesium-137 deposition dataset was assembled. Most of the airborne Chernobyl cesium was wet deposited, either via interception by falling raindrops or via absorption into cloud droplets destined to become raindrops. The Hybrid Single-Particle Lagrangian rated Transport (HYSPLIT) model, developed at Air Resources Laboratory, is used to simulate the transport and deposition of Chernobyl cesium-137. A cloud base parameterization modification is tested and appears to slightly improve the accuracy of one HYSPLIT simulation of daily Chernobyl cesium-137 deposition over the course of the accident at isolated European sites, and …

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Spectral And Temporal Characterization Of High Temperature Events, William F. Bagby Mar 2001

Spectral And Temporal Characterization Of High Temperature Events, William F. Bagby

Theses and Dissertations

The remote observations of the temporal and spectral characteristics of the infrared (IR) emissions from exploding ordnance have been correlated with explosion conditions. A Bomem MR-154 Fourier Transform Interferometer with two detectors, InSb and HgCdTe, was used to record spectra in the 1.3 - 20 micrometers range. Data was collected at spectral resolutions of 16/cm and 4/cm, and temporal resolutions of 0.045 sand 0.123 5, respectively. The data files range in size from 900 Kilobytes to several Megabytes. These are reduced to 2-dimensional representations of temporal features that are less than 100 Kilobytes. The data analysis indicates the possibility of …

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Validation And Assessment Of Dmsp Electron Temperatures In The Topside Ionosphere, Bradford S. Green Mar 2001

Validation And Assessment Of Dmsp Electron Temperatures In The Topside Ionosphere, Bradford S. Green

Theses and Dissertations

Geomagnetic disturbances in the near earth space environment can adversely affect numerous military and Department of Defense (DoD) systems and operations. To improve the prediction accuracy of such disturbances, the next generation of space environment forecast models aims to automatically ingest real-time ionospheric measurements. This research validates and assesses one such measurement - the Defense Military Satellite Program (DMSP) measured electron temperature (Te). DMSP Te data were validated against near simultaneous incoherent scatter radar (ISR) Te measurements from Millstone Hill, MA and Sondrestrom, Greenland between Winter 1996 and Summer 2000. Of the 37 Millstone and six …

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Analysis Of Cloud-Free Line-Of-Sight Probability Calculations, Joseph J. Golemboski Iii Mar 2001

Analysis Of Cloud-Free Line-Of-Sight Probability Calculations, Joseph J. Golemboski Iii

Theses and Dissertations

Cloud-free line-of-sight probabilities were calculated using two separate methods. The first was a variation of a method developed by the Rand Corporation in 1972. In it, CFLOS probabilities were calculated using empirical data based on five years of photograms taken over Columbia, Missouri and forecasted cloud amounts rather than climatological values. The second was a new approach using the Cloud Scene Simulation Model developed by Phillips Laboratory. Cloud scenes were generated using forecasted cloud fields, meteorological inputs, and thirty random numbers. Water content files were produced and processed through a follow-on program to determine the extinction coefficients at each grid …

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Analysis Of Cloud-To-Ground Lightning Clusters With Radar Composite Imagery, Rhonda B. Scott Mar 2001

Analysis Of Cloud-To-Ground Lightning Clusters With Radar Composite Imagery, Rhonda B. Scott

Theses and Dissertations

The most recent research conducted at the Air Force Institute of Technology involved studying a large volume of lightning data without coupling radar imagery (Parsons 2000). Parsons finding could not be acted on because no individual storms were studied. The primary goal of this research is to determine whether the techniques used by Parsons can be applied to storms by examining the radar imagery and lightning data. This research used the methodology applied to lightning data by Parsons and radar imagery to determine whether the location of lightning clusters were located near storms. A composite reflectivity radar image was generated …

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Investigation Of Gravity Waves Via The Rotational Temperature Of Hydroxyl Nightglow, Erin C. Willingham Mar 2001

Investigation Of Gravity Waves Via The Rotational Temperature Of Hydroxyl Nightglow, Erin C. Willingham

Theses and Dissertations

Measurement of the vibration and rotation bands of mesospheric hydroxyl radicals (OH) has been conducted during the past two decades using ground-based and space-based interferometers to take temperature and wind measurements from 70-100km in altitude. Gravity waves that pass through the mesosphere can be measured by determining the variance over time of the rotational temperature of the OH emissions. Several attempts were made to take spectrum measurements of the nightglow from hydroxyl radicals in the mesosphere using a custom hardware configuration that included a telescope and grating monochrometer optimized for the visible and near infrared. Quantifying gravity wave activity was …

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Assessment Of The Effects Of Entrainment And Wind Shear On Nuclear Cloud Rise Modeling, Daniel E. Zalewski Mar 2001

Assessment Of The Effects Of Entrainment And Wind Shear On Nuclear Cloud Rise Modeling, Daniel E. Zalewski

Theses and Dissertations

The Missile Defense Agency (MDA) plans to construct, during a two-week period, an X-Band Radar (XBR) on Shemya, AK. Wind speeds must not, at any time during the construction, exceed a 25 knot limit set by the MDA for lifting the massive dome panels into place. The goal of this research was to explore the possibilities of long-range forecasts to determine the feasibility of predicting any upcoming two-week windows of opportunity, well in advance, that will ensure the successful completion of constructing the XBR on Shemya. In order to reach this goal, the following objectives were achieved; (1) a climatological …

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Analyzing The Effects Of Meteorology On Radar Measured Index Of Refraction Structure Parameter, Jeffrey W. Budai Mar 2001

Analyzing The Effects Of Meteorology On Radar Measured Index Of Refraction Structure Parameter, Jeffrey W. Budai

Theses and Dissertations

Forecasting optical turbulence is essential for the Air Force's Airborne Laser program to optimize placement of aircraft. To find bow meteorology affects Cn2, the intensity of turbulence in the index of refraction, case studies of synoptically interesting times are first chosen. Correlation coefficients are then computed between radar measured Cn2 and meteorological quantities. The potential for mechanically turbulent activity is looked at. In the analysis of this work, six meteorological features were found likely to affect Cn2. Two features associated with affecting potential refractivity, and thus Cn2, are jets …

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