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Florida Institute of Technology

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Articles 91 - 120 of 179

Full-Text Articles in Oceanography and Atmospheric Sciences and Meteorology

Relativistic Electron Avalanches As A Thunderstorm Discharge Competing With Lightning, Nicole A. Kelley, David M. Smith, Joseph R. Dwyer, Michael Splitt, Steven Lazarus, Forest Martinez-Mckinney, Bryna Hazelton, Brian Grefenstette, Alexander Lowell, Hamid K. Rassoul Jan 2015

Relativistic Electron Avalanches As A Thunderstorm Discharge Competing With Lightning, Nicole A. Kelley, David M. Smith, Joseph R. Dwyer, Michael Splitt, Steven Lazarus, Forest Martinez-Mckinney, Bryna Hazelton, Brian Grefenstette, Alexander Lowell, Hamid K. Rassoul

Ocean Engineering and Marine Sciences Faculty Publications

Gamma-ray ‘glows’ are long duration (seconds to tens of minutes) X-ray and gamma-ray emission coming from thunderclouds. Measurements suggest the presence of relativistic runaway electron avalanches (RREA), the same process underlying terrestrial gamma-ray flashes. Here we demonstrate that glows are relatively a common phenomena near the tops of thunderstorms, when compared with events such as terrestrial gamma-ray flashes. Examining the strongest glow measured by the airborne detector for energetic emissions, we show that this glow is measured near the end of a downward RREA, consistent with occurring between the upper positive charge layer and the negative screening layer above it. …

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Evaluating The Surface Layer Wind Profile In The Wrf, Robert Stephen James Dec 2014

Evaluating The Surface Layer Wind Profile In The Wrf, Robert Stephen James

Theses and Dissertations

The purpose of this thesis is to investigate how the surface vertical wind profile responds to different planetary boundary layer schemes in computer models. Local surface roughness is one of the elements represented in these schemes, and is used when interpolating winds down from the lowest model level to the surface, so this needs to be accurately represented in the model. Computer models rely on one bulk estimate of surface roughness for a given grid point, despite the complexity of surrounding terrain. Data for this research was gathered from local surface observations and computer simulations, which looked at two different …

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Probability Distributions And Threshold Selection For Monte Carlo–Type Tropical Cyclone Wind Speed Forecasts, Steven M. Lazarus, Michael E. Splitt, Sarah Collins, Denis N. Botambekov, William P. Roeder Apr 2014

Probability Distributions And Threshold Selection For Monte Carlo–Type Tropical Cyclone Wind Speed Forecasts, Steven M. Lazarus, Michael E. Splitt, Sarah Collins, Denis N. Botambekov, William P. Roeder

Aeronautics Faculty Publications

Probabilistic wind speed forecasts for tropical cyclones from Monte Carlo–type simulations are assessed within a theoretical framework for a simple unbiased Gaussian system that is based on feature size and location error that mimic tropical cyclone wind fields. Aspects of the wind speed probability data distribution, including maximumexpected probability and forecast skill, are assessed. Wind speed probability distributions are shown to be well approximated by a bounded power-law distribution when the feature size is smaller than the location error and tends toward a U-shaped distribution as the location error becomes small. Forecast skill (i.e., true and Heidke skill scores) is …

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A Depth Refugium From Catastrophic Coral Bleaching Prevents Regional Extinction, Tyler B. Smith, Peter W. Glynn, Juan L. Maté, Lauren T. Toth, Joanna Gyory Jan 2014

A Depth Refugium From Catastrophic Coral Bleaching Prevents Regional Extinction, Tyler B. Smith, Peter W. Glynn, Juan L. Maté, Lauren T. Toth, Joanna Gyory

Ocean Engineering and Marine Sciences Faculty Publications

Species intolerant of changing climate might avoid extinction within refugia buffered from extreme conditions. Refugia have been observed in the fossil record but are not well documented or understood on ecological time scales. Using a 37-year record from the eastern Pacific across the two most severe El Nin˜ o events on record (1982–1983 and 1997– 1998) we show how an exceptionally thermally sensitive reef-building hydrocoral, Millepora intricata, twice survived catastrophic bleaching in a deeper-water refuge (.11 m depth). During both events, M. intricata was extirpated across its range in shallow water, but showed recovery within several years, while two other …

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Comparing Biofouling Control Treatments For Use On Aquaculture Nets, Geoffrey Swain, Nagahiko Shinjo Jan 2014

Comparing Biofouling Control Treatments For Use On Aquaculture Nets, Geoffrey Swain, Nagahiko Shinjo

Ocean Engineering and Marine Sciences Faculty Publications

Test panels comprised of uncoated, copper coated and silicone coated 7/8'' (22 mm) mesh knitted nylon net were evaluated to compare their properties and the effectiveness to prevent biofouling. This paper describes test procedures that were developed to quantify the performance in terms of antifouling, cleanability, drag and cost. The copper treatment was the most effective at controlling fouling, however, the silicone treated nets were the easiest to clean. The drag forces on the net were a function of twine diameter, twine roughness and fouling. After immersion, the uncoated nets had the most drag followed by the silicone and copper …

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Corals On Acid: An Inquiry-Based Activity Leading Students To A Better Understanding Of Ocean Acidification Impacts, Casey L. Boleman, Philip M. Gravinese, Ellen N. Muse, Andrea E. Marston, John G. Windsor Dec 2013

Corals On Acid: An Inquiry-Based Activity Leading Students To A Better Understanding Of Ocean Acidification Impacts, Casey L. Boleman, Philip M. Gravinese, Ellen N. Muse, Andrea E. Marston, John G. Windsor

Ocean Engineering and Marine Sciences Faculty Publications

The objective of this inquiry-based lesson is for students to gain an understanding of how increasing ocean acidity can affect the calcification of marine organisms. During this activity, students: (1) design an experiment to quantify the CaCO3 concentration of two invertebrate skeletal samples, one that has been soaked in normal seawater and another in a low pH solution, and (2) use critical thinking and discussion to evaluate possible explanations for the difference in the skeletal CaCO3 compositions. Our lesson focuses on exploring the activity before ocean acidification is introduced to provide a common conceptual framework to engage students.

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Evaluation Of A Wind-Wave System For Ensemble Tropical Cyclone Wave Forecasting. Part I: Winds, Steven M. Lazarus, Samuel T. Wilson, Michael E. Splitt, Gary A. Zarillo Apr 2013

Evaluation Of A Wind-Wave System For Ensemble Tropical Cyclone Wave Forecasting. Part I: Winds, Steven M. Lazarus, Samuel T. Wilson, Michael E. Splitt, Gary A. Zarillo

Aeronautics Faculty Publications

A computationally efficient method of producing tropical cyclone (TC) wind analyses is developed and tested, using a hindcast methodology, for 12 Gulf of Mexico storms. The analyses are created by blending synthetic data, generated from a simple parametric model constructed using extended best-track data and climatology, with a first-guess field obtained from the NCEP-NCAR North American Regional Reanalysis (NARR). Tests are performed whereby parameters in the wind analysis and vortex model are varied in an attempt to best represent the TC wind fields. A comparison between nonlinear and climatological estimates of the TC size parameter indicates that the former yields …

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Evaluation Of A Wind-Wave System For Ensemble Tropical Cyclone Wave Forecasting. Part Ii: Waves, Steven M. Lazarus, Samuel T. Wilson, Michael E. Splitt, Gary A. Zarillo Apr 2013

Evaluation Of A Wind-Wave System For Ensemble Tropical Cyclone Wave Forecasting. Part Ii: Waves, Steven M. Lazarus, Samuel T. Wilson, Michael E. Splitt, Gary A. Zarillo

Ocean Engineering and Marine Sciences Faculty Publications

A wind-wave forecast system, designed with the intention of generating unbiased ensemble wave forecasts for extreme wind events, is assessed. Wave hindcasts for 12 tropical cyclones (TCs) are forced using a wind analysis produced from a combination of the North American Regional Reanalysis (NARR) and a parametric wind model. The default drag parameterization is replaced by one that is more in line with recent studies where a cap at weak-to-moderate wind speeds is applied. Quadrant-based significant wave height (Hs) statistics are composited in a storm-relative reference frame and stratified by the radius of maximum wind, storm speed, and storm intensity. …

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Evaluation Of A Wind-Wave System For Ensemble Tropical Cyclone Wave Forecasting. Part I: Winds, Steven M. Lazarus, Samuel T. Wilson, Michael E. Splitt, Gary A. Zarillo Apr 2013

Evaluation Of A Wind-Wave System For Ensemble Tropical Cyclone Wave Forecasting. Part I: Winds, Steven M. Lazarus, Samuel T. Wilson, Michael E. Splitt, Gary A. Zarillo

Ocean Engineering and Marine Sciences Faculty Publications

A computationally efficient method of producing tropical cyclone (TC) wind analyses is developed and tested, using a hindcast methodology, for 12 Gulf of Mexico storms. The analyses are created by blending synthetic data, generated from a simple parametric model constructed using extended best-track data and climatology, with a first-guess field obtained from the NCEP-NCAR North American Regional Reanalysis (NARR). Tests are performed whereby parameters in the wind analysis and vortex model are varied in an attempt to best represent the TC wind fields.Acomparison between nonlinear and climatological estimates of the TC size parameter indicates that the former yields a much …

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Radio Signals From Electron Beams In Terrestrial Gamma Ray Flashes, Valerie Connaughton, Joseph R. Dwyer, Eric Cramer Jan 2013

Radio Signals From Electron Beams In Terrestrial Gamma Ray Flashes, Valerie Connaughton, Joseph R. Dwyer, Eric Cramer

Aerospace, Physics, and Space Science Faculty Publications

We show that the rate of association between terrestrial gamma ray flashes (TGFs) observed by the Fermi gamma ray burst monitor and VLF discharges detected by the World Wide Lightning Location Network (WWLLN) depends strongly on the duration of the TGF, with the shortest TGFs having associated WWLLN events over 50% of the time, and the longest TGFs showing a less than 10% match rate. This correlation is stronger if one excludes the WWLLN discharges that are not simultaneous (within 200 ms) with the TGF. We infer that the simultaneous VLF discharges are from the relativistic electron avalanches that are …

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The Angular Distribution Of Energetic Electron And X-Ray Emissions From Triggered Lightning Leaders, M. M. Schaal, Joseph R. Dwyer, Hamid K. Rassoul, Jonathan David Hill, Douglas M. Jordan, Martin A. Uman Jan 2013

The Angular Distribution Of Energetic Electron And X-Ray Emissions From Triggered Lightning Leaders, M. M. Schaal, Joseph R. Dwyer, Hamid K. Rassoul, Jonathan David Hill, Douglas M. Jordan, Martin A. Uman

Aerospace, Physics, and Space Science Faculty Publications

We investigate individual X-ray bursts from lightning leaders to determine if energetic electrons at the source (and hence X-rays) are emitted isotropically or with some degree of anisotropy. This study was motivated by the work of Saleh et al. (2009), which found the falloff of X-rays in concentric radial annuli, covering all azimuthal directions in each annulus, from the lightning channel to be most consistent with an isotropic electron source. Here we perform a statistical analysis of angular and spatial distributions of X-rays measured by up to 21 NaI/PMT detectors at the International Center for Lightning Research and Testing site …

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Analysis Of The Experiment On Registration Of X-Rays From The Stepped Leader Of A Cloud-To-Ground Lightning Discharge, Leonid P. Babich, Igor M. Kutsyk, Evgeni N. Donsko, Joseph R. Dwyer Jan 2013

Analysis Of The Experiment On Registration Of X-Rays From The Stepped Leader Of A Cloud-To-Ground Lightning Discharge, Leonid P. Babich, Igor M. Kutsyk, Evgeni N. Donsko, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

Using a Monte Carlo technique to simulate the transport of runaway electrons (REs) and X-rays in the atmosphere and through attenuators covering detectors, we have modeled the results of experiments to detect X-rays from triggered lightning and stepped leaders of a natural cloud-to-ground lightning. In the model, bremsstrahlung of high-energy runaway electrons (REs) generated at the leader front is assumed to be the origin of X-rays. Specific fluxes (per one RE) of photons and bremsstrahlung energy at the detectors were calculated. The analysis was executed with monoenergetic and exponential initial energy distributions of REs with different angular distributions. To reproduce …

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Modeling Terrestrial Gamma Ray Flashes Produced By Relativistic Feedback Discharges, Ningyu Liu, Joseph R. Dwyer Jan 2013

Modeling Terrestrial Gamma Ray Flashes Produced By Relativistic Feedback Discharges, Ningyu Liu, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

This paper reports a modeling study of terrestrial gamma ray flashes (TGFs) produced by relativistic feedback discharges. Terrestrial gamma ray flashes are intense energetic radiation originating from the Earth’s atmosphere that has been observed by spacecraft. They are produced by bremsstrahlung interactions of energetic electrons, known as runaway electrons, with air atoms. An efficient physical mechanism for producing large fluxes of the runaway electrons to make the TGFs is the relativistic feedback discharge, where seed runaway electrons are generated by positrons and X-rays, products of the discharge itself. Once the relativistic feedback discharge becomes self-sustaining, an exponentially increasing number of …

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Radio Emissions From Terrestrial Gamma-Ray Flashes, Joseph R. Dwyer, Steven A. Cummer Jan 2013

Radio Emissions From Terrestrial Gamma-Ray Flashes, Joseph R. Dwyer, Steven A. Cummer

Aerospace, Physics, and Space Science Faculty Publications

The theory of radio frequency (RF) emissions by terrestrial gamma-ray flashes (TGFs) is developed. These radio emissions, which are separate from the emission caused by lightning, are produced by the electric currents generated by runaway electrons and resulting low-energy electrons and ions. It is found from theory that the radio frequency pulses produced by TGFs are large enough to measure. Features of these signals depend strongly on certain aspects of the runaway acceleration process and so should provide additional information about the source mechanism(s) of this interesting atmospheric phenomenon. The RF emissions from several TGF models are calculated and compared …

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Photographic Survey Of Benthos Provides Insights Into The Antarctic Fish Fauna From The Marguerite Bay Slope And The Amundsen Sea, Joseph T. Eastman, Margaret O. Amsler, Richard D. Aronson, Sven Thatje, James Mcclintock, Stephanie C. Vos, Jeffrey W. Kaeli, Hanumant Singh, Mario La Mesa Jan 2013

Photographic Survey Of Benthos Provides Insights Into The Antarctic Fish Fauna From The Marguerite Bay Slope And The Amundsen Sea, Joseph T. Eastman, Margaret O. Amsler, Richard D. Aronson, Sven Thatje, James Mcclintock, Stephanie C. Vos, Jeffrey W. Kaeli, Hanumant Singh, Mario La Mesa

Ocean Engineering and Marine Sciences Faculty Publications

We reviewed photographic images of fishes from depths of 381–2282m in Marguerite Bay and 405–2007m in the Amundsen Sea. Marguerite Bay fishes were 33% notothenioids and 67% non-notothenioids. Channichthyids (47%) and nototheniids (44%) were the most abundant notothenioids. The deep-living channichthyid Chionobathyscus dewitti (74%) and the nototheniid genus Trematomus (66%) were the most abundant taxa within these two families. The most abundant non-notothenioids were the macrourid Macrourus whitsoni (72%) and zoarcids (18%). Amundsen Sea fishes were 87% notothenioids and 13% non-notothenioids, the latter exclusively Macrourus whitsoni. Bathydraconids (38%) and artedidraconids (30%) were the most abundant notothenioids. We observed that Macrourus …

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Relative Roles Of Circumnavigating Waves And Extratropics On The Mjo And Its Relationship With The Mean State, Pallav Ray, Tim Li Jan 2013

Relative Roles Of Circumnavigating Waves And Extratropics On The Mjo And Its Relationship With The Mean State, Pallav Ray, Tim Li

Ocean Engineering and Marine Sciences Faculty Publications

Aset of atmospheric general circulation model (GCM) experiments is designed to explore the relative roles of the circumnavigating waves and the extratropics on the Madden–Julian oscillation (MJO). In a ‘‘control’’ simulation, the model is forced by the climatological monthly sea surface temperature for 20 yr. In the first sensitivity experiment, model prognostic variables are relaxed in the tropical Atlantic region (208S–208N, 808W–08) toward the ‘‘controlled’’ climatological annual cycle to suppress the influences from the circumnavigating waves. In the second sensitivity experiment, model prognostic variables are relaxed in the 208–308 latitude zones toward the controlled climatological annual cycle to suppress the …

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Catastrophe And The Life Span Of Coral Reefs, Richard B. Aronson, William F. Precht, Ian G. Macintyre, Lauren T. Toth Jan 2012

Catastrophe And The Life Span Of Coral Reefs, Richard B. Aronson, William F. Precht, Ian G. Macintyre, Lauren T. Toth

Ocean Engineering and Marine Sciences Faculty Publications

A strong earthquake in the western Caribbean in 2009 had a catastrophic impact on uncemented, unconsolidated coral reefs in the central sector of the shelf lagoon of the Belizean barrier reef. In a set of 21 reef sites that had been observed prior to the earthquake, the benthic assemblages of 10 were eradicated, and one was partially damaged, by avalanching of their slopes. Ecological dynamics that had played out over the previous 23 years, including the mass mortalities of two sequentially dominant coral species and a large increase in the cover of an encrusting sponge, were instantaneously rendered moot in …

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Power Estimates Associated With Internal Tides From The Monterey Bay Area, Steven M. Jachec Jan 2012

Power Estimates Associated With Internal Tides From The Monterey Bay Area, Steven M. Jachec

Ocean Engineering and Marine Sciences Faculty Publications

Numerical modeling has proven to be a useful method for simulating internal tides within the coastal ocean. Monterey Bay is a location that experiences energetic semidiurnal internal tides, and they are pronounced within Monterey Submarine Canyon. Numerical simulations and field measurements indicate that the baroclinic energy fluxes there are spatially variable, leading to locations of positive and negative baroclinic energy flux divergences. Results derived from a SUNTANS (Stanford Unstructured Nonhydrostatic Terrain-following Adaptive Navier-Stokes Simulator) model simulation show that Monterey Submarine Canyon’s baroclinic power is net dissipative (–8.3 MW). However, sources and sinks exist throughout the canyon, and they permeate the …

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Improving High-Resolution Model Forecasts Of Downslope Winds In The Las Vegas Valley, Andre K. Pattantyus, Sen Chiao, Stanley Czyzyk Jun 2011

Improving High-Resolution Model Forecasts Of Downslope Winds In The Las Vegas Valley, Andre K. Pattantyus, Sen Chiao, Stanley Czyzyk

Ocean Engineering and Marine Sciences Faculty Publications

Numerical simulations for severe downslope winds as well as trapped lee waves in Nevada’s Las Vegas Valley were performed in this study. The goal of this study was to improve model forecasts of downslope wind- event intensities. This was measured by assessing different planetary boundary layer (PBL) schemes in the mountain–valley region. The Weather Research and Forecasting Model was adopted for this research. The numerical experiments were constructed using two nested domains, with 4- and 1-km grid resolution. The working hypothesis was that the occurrence of low-level wind shear and surface gustiness in the Las Vegas Valley was guided by …

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The Lightning-Tgf Relationship On Microsecond Ttimescales, Steven A. Cummer, Gaopeng Lu, Michael S. Briggs, Valerie Connaughton, Shaolin Xiong, Gerald Jerry Fishman, Joseph R. Dwyer Jan 2011

The Lightning-Tgf Relationship On Microsecond Ttimescales, Steven A. Cummer, Gaopeng Lu, Michael S. Briggs, Valerie Connaughton, Shaolin Xiong, Gerald Jerry Fishman, Joseph R. Dwyer

Aerospace, Physics, and Space Science Faculty Publications

We analyze the count rates of two terrestrial gamma-ray flashes (TGFs) detected by the Fermi Gamma-ray Burst Monitor (GBM) with the broadband magnetic fields (1 to 300 kHz) produced by the simultaneous lightning processes. The microsecond-scale absolute time accuracy for these data, combined with independent geolocations of the source lightning, enable this analysis with higher accuracy than previously possible. In both events, fast discharge-like processes occur within several tens of microseconds of the gamma-ray generation, although not with a consistent relationship. The magnetic field data also show a slower signal component produced by a source current that in both events …

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High-Speed X-Ray Images Of Triggered Lightning Dart Leaders, Joseph R. Dwyer, M. M. Schaal, Hamid K. Rassoul, Martin A. Uman, Douglas M. Jordan, Dustin Hill Jan 2011

High-Speed X-Ray Images Of Triggered Lightning Dart Leaders, Joseph R. Dwyer, M. M. Schaal, Hamid K. Rassoul, Martin A. Uman, Douglas M. Jordan, Dustin Hill

Aerospace, Physics, and Space Science Faculty Publications

We present the first high-time resolution two-dimensional images of X-ray emissions from lightning. The images were recorded at a rate of 10 million per second using a new pinhole-type camera, located 44 m from rocket-and-wire- triggered lightning. We report observations of two dart leaders, one in each of two lightning flashes triggered during the summer of 2010 in north-central Florida. In both events, as the dart leader approached the ground, the X-ray source was also seen to descend along the previous lightning channel. For the second event, the X-ray source exhibited a downward speed of 4.5 × 10 7 m/s, …

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Novel Optical Remote Sensing Technology For Prediction Of Harmful Algal Blooms, Elizabeth Tobin Jan 2011

Novel Optical Remote Sensing Technology For Prediction Of Harmful Algal Blooms, Elizabeth Tobin

Link Foundation Ocean Engineering and Instrumentation Fellowship Reports

Harmful Algal Blooms (HABs) are outbreaks of planktonic algae that threaten public health, degrade aquatic ecosystems and cause major economic losses. Most HABs are detected only after they reach an advanced stage, when they have already caused significant ecological and economic damage. However, many HAB-forming species have two distinct life stages, a dormant benthic stage and a vegetative pelagic stage.The primary objective of this project was to construct and test a prototype of an autonomous optical sensor for the detection and characterization of HAB-forming algae as they emerge from the sediments.

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A Terrestrial Gamma Ray Flash Observed From An Aircraft, D. M. Smith, Michael E. Splitt, Steven M. Lazarus Jan 2011

A Terrestrial Gamma Ray Flash Observed From An Aircraft, D. M. Smith, Michael E. Splitt, Steven M. Lazarus

Aerospace, Physics, and Space Science Faculty Publications

On 21 August 2009, the Airborne Detector for Energetic Lightning Emissions (ADELE), an array of six gamma-ray detectors, detected a brief burst of gamma rays while flying aboard a Gulfstream V jet near two active thunderstorm cells. The duration and spectral characteristics of the event are consistent with the terrestrial gamma ray flashes (TGFs) seen by instruments in low Earth orbit. A long-duration, complex +IC flash was taking place in the nearer cell at the same time, at a distance of ∼10 km from the plane. The sferics that are probably associated with this flash extended over 54 ms and …

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Integration, Testing And Calibration Of Imaging Systems For Land & Water Remote Sensing, Charles R. Bostater, James Jones, Heather Frystacky, Mate Kovacs, Oszkar Jozsa Oct 2010

Integration, Testing And Calibration Of Imaging Systems For Land & Water Remote Sensing, Charles R. Bostater, James Jones, Heather Frystacky, Mate Kovacs, Oszkar Jozsa

Ocean Engineering and Marine Sciences Faculty Publications

Imagery is presented along with calibration and testing procedures of several airborne imaging systems. The low altitude airborne systems include a cooled hyperspectral imaging system with 1024 spectral channels and 1375 spatial pixels. The hyperspectral imaging system is collocated with a full resolution high definition video recorder for simultaneous HD video imagery, 12.3 megapixel digital images for multispectral "sharpening" the hyperspectral imagery, or large frame 9 inch film cameras yield scanned aerial imagery with approximately 2200 by 2200 pixel multispectral imagery. Two high spectral (252 channels) and radiometric sensitivity solid state spectrographs are used for collecting upwelling radiance (sub-meter pixels) …

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Evaluation Of Data Reduction Algorithms For Real-Time Analysis, Steven M. Lazarus, Michael E. Splitt, Michael D. Lueken, Rahul Ramachandran, Xiang Li, Sunil Movva, Sara J. Graves, Bradley T. Zavodsky Jun 2010

Evaluation Of Data Reduction Algorithms For Real-Time Analysis, Steven M. Lazarus, Michael E. Splitt, Michael D. Lueken, Rahul Ramachandran, Xiang Li, Sunil Movva, Sara J. Graves, Bradley T. Zavodsky

Ocean Engineering and Marine Sciences Faculty Publications

Data reduction tools are developed and evaluated using a data analysis framework. Simple (nonadaptive) and intelligent (adaptive) thinning algorithms are applied to both synthetic and real data and the thinned datasets are ingested into an analysis system. The approach is motivated by the desire to better represent highimpact weather features (e.g., fronts, jets, cyclones, etc.) that are often poorly resolved in coarse-resolution forecast models and to efficiently generate a set of initial conditions that best describes the current state of the atmosphere. As a precursor to real-data applications, the algorithms are applied to one- and two-dimensional synthetic datasets. Information gleaned …

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Numerical Investigations On The Formation Of Tropical Storm Debby During Namma-06, Sen Chiao, Gregory S. Jenkins Jun 2010

Numerical Investigations On The Formation Of Tropical Storm Debby During Namma-06, Sen Chiao, Gregory S. Jenkins

Ocean Engineering and Marine Sciences Faculty Publications

Mesoscale model forecasts were carried out beginning at 0000 UTC 19 August for simulating Tropical Disturbance 4, which was named Tropical Storm Debby on 22 August 2006. The Weather Research and Forecasting model, with 25-km grid spacing and an inner nested domain of 5-km grid spacing, was used. The development of a small closed vortex at approximately 0600UTC20 August 2006 at 850 hPa was found off the coast of Guinea in agreement with satellite images in the 5-km simulation. Intense convection offshore and over the Guinea Highlands during the morning of 20 August 2006 led to the production of a …

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Evaluation Of The National Hurricane Center’S Tropical Cyclone Wind Speed Probability Forecast Product, Michael E. Splitt, Jaclyn A. Shafer, Steven M. Lazarus, William P. Roeder Apr 2010

Evaluation Of The National Hurricane Center’S Tropical Cyclone Wind Speed Probability Forecast Product, Michael E. Splitt, Jaclyn A. Shafer, Steven M. Lazarus, William P. Roeder

Ocean Engineering and Marine Sciences Faculty Publications

A tropical cyclone (TC) wind speed probability forecast product developed at the Cooperative Institute for Research in the Atmosphere (CIRA) and adopted by the National Hurricane Center (NHC) is evaluated for U.S. land-threatening and landfalling events over four hurricane seasons from 2004 to 2007. A key element of this work is the discernment of risk associated with the interval forecast probabilities for the three wind speed categories (i.e., 34, 50, and 64 kt, where 1 kt = 0.52 m s−1). A quantitative assessment of the interval probabilities (0–12, 12–24, 24–36, 36–48, 48–72, 72–96, and 96–120 h) is conducted by converting …

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Model Of Sprite Luminous Trail Caused By Increasing Streamer Current, Ningyu Liu Jan 2010

Model Of Sprite Luminous Trail Caused By Increasing Streamer Current, Ningyu Liu

Aerospace, Physics, and Space Science Faculty Publications

This study investigates a possible physical mechanism responsible for the occurrence of the luminous trail of sprite streamers, which is also known as "afterglow." According to streamer modeling results, when sprite streamers propagate with expansion, acceleration and brightening, the total current flowing through the streamer body also increases. The increasing current results in the rise of the electric field in the streamer channel far behind the streamer head, which leads to effective production of N₂ excited states by electron impact excitation and then the glowing trail.

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Image Analysis For Water Surface & Subsurface Feature Detection In Shallow Waters, Charles R. Bostater Jr., James Jones, Heather Frystacky, Mate Kovacs, Oszkar Jozsa Jan 2010

Image Analysis For Water Surface & Subsurface Feature Detection In Shallow Waters, Charles R. Bostater Jr., James Jones, Heather Frystacky, Mate Kovacs, Oszkar Jozsa

Ocean Engineering and Marine Sciences Faculty Publications

Carefully collected airborne imagery demonstrates the ability to see water surface features as well as shallow bottom features such as submerged vegetation and manmade targets. Traditional photogrammetric imagery and airborne digital imagery both suffer from a loss in image clarity due to a number of factors, including capillary and small gravity waves, the water column or in-situ constituents. The use of submerged as well as surface man-made calibration targets deployed during airborne or in-situ subsurface image acquisitions forms a preliminary basis for correcting imagery in order to improve subsurface and surface features and their detection. Methods presented as well as …

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Tsunami Hazard And Total Risk In The Caribbean Basin, X. William Proenza, George A. Maul Jan 2010

Tsunami Hazard And Total Risk In The Caribbean Basin, X. William Proenza, George A. Maul

Ocean Engineering and Marine Sciences Faculty Publications

Deadly western North Atlantic Ocean tsunami events in the last centuries have occurred along the east coast of Canada, the United States, most Caribbean islands, and the North Atlantic Coast of South America. The catastrophic Indian Ocean tsunami of 2004 reminded natural hazards managers that tsunami risk is endemic to all oceans. Total Risk is defined as hazard (frequency of tsunami events) times measures of elements at risk (human exposure) times measures of vulnerability (preparedness) in a given epoch (Nott, 2006). While the tsunami hazard in the Caribbean (averaging 19 ± 22 years between deadly events) is lower than Pacific …

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