Physical Sciences and Mathematics Commons^™

Comparison Of The X-Track Altimetry Estimated Currents With Moored Adcp And Hf Radar Observations On The West Florida Shelf, Yonggang Liu, Robert H. Weisberg, Stefano Vignudelli, Laurent Roblou, Clifford R. Merz

Yonggang Liu

The performance of coastal altimetry over a wide continental shelf is assessed using multiple-year ocean current observations by moored Acoustic Doppler Current Profilers (ADCP) and high-frequency (HF) radar on the West Florida Shelf. Across-track, surface geostrophic velocity anomalies, derived from the X-TRACK along-track sea level anomalies are compared with the near surface current vector components from moored ADCP observations at mid shelf. The altimeter-derived velocity anomalies are also directly compared with the HF radar surface current vector radial components that are aligned perpendicular to the satellite track. Preliminary results indicate the potential usefulness of the along-track altimetry data in contributing …

Seasonal Variability On The West Florida Shelf, Yonggang Liu, Robert H. Weisberg

Yonggang Liu

The seasonal variations of the West Florida Continental Shelf (WFS) circulation and sea level are described using observations of velocity from an array of moored acoustic Doppler current profilers and various ancillary data. With record lengths ranging from 3 years to over a decade, a robust seasonal cycle in velocity is found, which varies across the shelf in a dynamically sensible way. Over most of the inner shelf these seasonal variations are primarily in response to local forcing, through Ekman-geostrophic spin-up, as previously found for the synoptic scale variability. Thus the inner shelf circulation is predominantly upwelling favorable from fall …

Tracking The Deepwater Horizon Oil Spill: A Modeling Perspective, Yonggang Liu, Robert H. Weisberg, Chuanmin Hu, Lianyuan Zheng

Yonggang Liu

The Deepwater Horizon oil spill was caused by a drilling rig explosion on 20 April 2010 that killed 11 people. It was the largest oil spill in U.S. history and presented an unprecedented threat to Gulf of Mexico marine resources. Although oil gushing to the surface diminished after the well was capped, on 15 July 2010, much remains to be known about the oil and the dispersants beneath the surface, including their trajectories and effects on marine life. A system for tracking the oil, both at the surface and at depth, was needed for mitigation efforts and ship survey guidance. …

Evaluation Of Trajectory Modeling In Different Dynamic Regions Using Normalized Cumulative Lagrangian Separation, Yonggang Liu, Robert H. Weisberg

Yonggang Liu

The Lagrangian separation distance between the endpoints of simulated and observed drifter trajectories is often used to assess the performance of numerical particle trajectory models. However, the separation distance fails to indicate relative model performance in weak and strong current regions, such as a continental shelf and its adjacent deep ocean. A new skill score is proposed based on the cumulative Lagrangian separation distances normalized by the associated cumulative trajectory lengths. This skill score is used to evaluate surface trajectories implied by Global HYCOM hindcast surface currents as gauged against actual satellite-tracked drifter trajectories in the eastern Gulf of Mexico …

Evolution Of The Loop Current System During The Deepwater Horizon Oil Spill Event As Observed With Drifters And Satellites, Yonggang Liu, Robert H. Weisberg, Charles Kovach, Rolf Riethmüller

Yonggang Liu

The ocean circulation patterns of the Gulf of Mexico (GOM) Loop Current (LC) system and their effects on the advection of the oil discharged during the Deepwater Horizon incident are described using in situ surface drifter trajectories and satellite observations from May to August 2010. These observations include altimetry-derived surface geostrophic velocities, sea surface temperature, ocean color, and surface oil locations. The elongated, northwestward penetrating LC retreated back from its northernmost position in late April 2010 and stayed farther away from the surface oil in the north during May 2010. Although the main body of the surface oil slick remained …

Hf Radar Performance In A Low-Energy Environment: Codar Seasonde Experience On The West Florida Shelf, Yonggang Liu, Robert H. Weisberg, Clifford R. Merz, Sage Litchtenwalner, Gary J. Kirkpatrick

Yonggang Liu

Three long-range (5 MHz) Coastal Ocean Dynamics Application Radar (CODAR) SeaSonde HF radars overlooking an array of as many as eight moored acoustic Doppler current profilers (ADCPs) have operated on the West Florida Shelf since September 2003 for the purpose of observing the coastal ocean currents. HF radar performance on this low-energy (currents and waves) continental shelf is evaluated with respect to data returns, the rms differences between the HF radar and the ADCP radial currents, bearing offsets, and radial velocity uncertainties. Possible environmental factors affecting the HF radar performance are discussed, with the findings that both the low-energy sea …

West Florida Shelf Mean Circulation Observed With Long-Term Moorings, Robert H. Weisberg, Yonggang Liu, Dennis A. Mayer

Yonggang Liu

The mean circulation on the West Florida Continental Shelf is described using long-term current measurements. Bounded by the Florida peninsula to the east and the Gulf of Mexico to the west, the West Florida Continental Shelf mean flow is oriented approximately along-isobath and southward. The mean velocity vectors veer systematically with depth, shoreward over shallow water and seaward over deeper water. This polarization change implies that the mean flow is upwelling over shallow water and downwelling seaward from the inner shelf. Such a well-organized, three-dimensional coastal ocean circulation pattern, revealed by an unprecedented set of observations, and explained on the …

Why We Do It – The University Of South Florida Tampa Library’S Commitment To Open-Access Publishing, Todd A. Chavez

Todd A. Chavez

The University of South Florida Tampa Library's support for open-access content is part of the organization's mission to advance scholarly communication generally and an important element of the Karst Information Portal initiative. As the costs associated with journal subscriptions increase and pressures to ensure unfettered access to high-quality, peer-reviewed research mount, research libraries must partner with scholars to establish sustainable open-access publishing models.

Patterns Of Upper Layer Circulation Variability In The South China Sea From Satellite Altimetry Using The Self-Organizing Map, Yonggang Liu, Robert H. Weisberg, Yaochu Yuan

Yonggang Liu

Patterns of the South China Sea (SCS) circulation variability are extracted from merged satellite altimetry data from October 1992 through August 2004 by using the self-organizing map (SOM). The annual cycle, seasonal and inter-annual variations of the SCS surface circulation are identified through the evolution of the characteristic circulation patterns. The annual cycle of the SCS gener- al circulation patterns is described as a change between two opposite basin-scale SW-NE oriented gyres embedded with eddies: low sea surface height anomaly (SSHA) (cyclonic) in winter and high SSHA (anticyclonic) in summer half year. The transition starts from July--August (January--February) with a …

Superior Karst Management Through Superior Data Management: The Karst Information Portal, E. Spencer Fleury, George H. Veni, Todd A. Chavez, Penelope J. Boston, Diana E. Northup, H. Len Vacher, Pat Seiser

Todd A. Chavez

Effective stewardship of caves and karst areas requires access to and efficient analysis of a diverse range of information. Vital data are scattered throughout specialty mainstream journals, which even for a single project could include fields such as ecology, hydrogeology, contaminant transport, toxicology, engineering geology and law. Additionally, volumes of crucial information often lie in diffi­cult-to-find gray literature. Management recommendations and decisions should be based on assessments of state-of-the-art information, but fall short when im­portant patterns and relationships are overlooked.

The Karst Information Portal (KIP) offers a solution to these problems. Con­ceived in 2005 and launched in June 2007, KIP …

Rectification Of The Bias In The Wavelet Power Spectrum, Yonggang Liu, X. San Liang, Robert H. Weisberg

Yonggang Liu

This paper addresses a bias problem in the estimate of wavelet power spectra for atmospheric and oceanic datasets. For a time series comprised of sine waves with the same amplitude at different frequencies the conventionally adopted wavelet method does not produce a spectrum with identical peaks, in contrast to a Fourier analysis. The wavelet power spectrum in this definition, that is, the transform coefficient squared (to within a constant factor), is equivalent to the integration of energy (in physical space) over the influence period (time scale) the series spans. Thus, a physically consistent definition of energy for the wavelet power …

Current Patterns On The West Florida Shelf From Joint Self-Organizing Map Analyses Of Hf Radar And Adcp Data, Yonggang Liu, Robert H. Weisberg, Lynn K. Shay

Yonggang Liu

To assess the spatial structures and temporal evolutions of distinct physical processes on the West Florida Shelf, patterns of ocean current variability are extracted from a joint HF radar and ADCP dataset acquired from August to September 2003 using Self-Organizing Map (SOM) analyses. Three separate ocean– atmosphere frequency bands are considered: semidiurnal, diurnal, and subtidal. The currents in the semidiurnal band are relatively homogeneous in space, barotropic, clockwise polarized, and have a neap-spring modulation consistent with semidiurnal tides. The currents in the diurnal band are less homogeneous, more baroclinic, and clockwise polarized, consistent with a combination of diurnal tides and …

The Impact Of Grey Literature In Advancing Global Karst Research: An Information Needs Assessment For A Globally Distributed Interdisciplinary Community, Todd A. Chavez, Anna H. Perrault, Pete Reehling, Courtney Crummett

Anna H. Perrault

A survey of the global karst community was conducted in 2006. The survey was distributed via the World Wide Web to known karst researchers. The instrument was designed to generate an initial inventory of core grey information types, to assess levels of usage of grey information by the respondents, and to gauge the karst community’s willingness to participate in building and expanding both this collection and the associated controlled vocabularies.

The Impact Of Grey Literature In Advancing Global Karst Research: An Information Needs Assessment For A Globally Distributed Interdisciplinary Community, Todd A. Chavez, Anna H. Perrault, Pete Reehling, Courtney Crummett

Todd A. Chavez

A survey of the global karst community was conducted in 2006. The survey was distributed via the World Wide Web to known karst researchers. The instrument was designed to generate an initial inventory of core grey information types, to assess levels of usage of grey information by the respondents, and to gauge the karst community’s willingness to participate in building and expanding both this collection and the associated controlled vocabularies.

Sea Surface Temperature Patterns On The West Florida Shelf Using Growing Hierarchical Self-Organizing Maps, Yonggang Liu, Robert H. Wesiberg, Ruoying He

Yonggang Liu

Neural network analyses based on the self-organizing map (SOM) and the growing hierarchical self-organizing map (GHSOM) are used to examine patterns of the sea surface temperature (SST) variability on the West Florida Shelf from time series of daily SST maps from 1998 to 2002. Four characteristic SST patterns are extracted in the first-layer GHSOM array: winter and summer season patterns, and two transitional patterns. Three of them are further expanded in the second layer, yielding more detailed structures in these seasons. The winter pattern is one of low SST, with isotherms aligned approximately along isobaths. The summer pattern is one …

Momentum Balance Diagnoses For The West Florida Shelf, Yonggang Liu, Robert H. Weisberg

Yonggang Liu

The momentum balance over the West Florida Shelf is diagnosed using observations of currents, bottom pressures, temperatures, winds, and coastal sea levels, along with hydrographic data from 32 monthly cruises spanning summer 1998 to winter 2001. Over synoptic weather time scales, the depth-averaged across-shelf momentum balance on the inner shelf is essentially geostrophic with smaller contributions from the across-shelf wind stress and other terms. Coherence analyses show that 95% of the acceleration (Coriolis and local) variance may be accounted for by the pressure gradient and friction (surface and bottom) over the synoptic weather band. The balances are more complicated on …

The Reflection Of Karst In The Online Mirror: A Survey Within Scientific Databases, 1960-2005, Lee J. Florea, Beth Fratesi, Todd A. Chavez

Todd A. Chavez

The field of cave and karst science is served by a literature that is dispersed across far-flung topical journals, government publications, and club newsletters. As part of an inter-institutional project to globalize karst information (KIP, the Karst Information Portal), the USF Library undertook a structured battery of literature searches to map the domain of karst literature. The study used 4,300 individual searches and four literature databases: GeoRef, BIOSIS, Anthropology Plus, and GPO Access. The searches were based on a list of 632 terms including 321 karst-related keywords culled from three leading encyclopedias and glossaries of cave and karst science. An …