Vladimir A. Paramygin

On the Design of Virtual Machine Sandboxes for Distributed Computing in Wide-area Overlays of Virtual Workstations

With recent advances in virtual computing and the revelation that compute-intensive tasks run well on system virtual machines (VMs), the ability to develop, deploy, and manage distributed systems has been ameliorated. This paper explores the design space of VM-based sandboxes where the following techniques that facilitate the deployment of secure nodes in wide-area overlays of virtual workstations (WOWs) are employed: DHCP-based virtual IP address allocation, self-configuring virtual networks supporting peer-to-peer NAT traversal, stacked file systems, and IPsec-based host authentication and end-to-end encryption of communication channels. Experiments with implementations of single-image VM sandboxes, which incorporate the above features and are easily deployable on hosted I/O VMMs, show execution time overheads of 10.6% or less for a batch- oriented CPU-intensive benchmark.

Circulation and Flushing in the Lagoonal System of the Guana Tolomato Matanzas National Estuarine Research Reserve (GTMNERR), Florida

Abstract Circulation and flushing inside the lagoon system of Guana Tolomato Matanzas National Estuarine Research Reserve (GTMNERR or GTM) have been studied using a three-dimensional numerical circulation model CH3D. The lagoon system includes two tidal inlets (St. Augustine Inlet and Matanzas Inlet). To ensure accuracy in model results, we extend the model domain to include a large portion of the coastal water and the Ponce de Leon Inlet in the south. Water levels on the open boundaries are provided by the East Coast (2001) ADCIRC Tidal Database. Model simulations of barotropic and baroclinic circulation from April 1 to May 31, 2004, produced reasonable water levels at numerous stations inside the GTM. Simulated salinity results are not as good because of the lack of freshwater inflow data inside the GTM and salinity data offshore. Using the simulated flow fields, we solve the three-dimensional transport equations for conservative species, and determine the flushing characteristics inside the GTM in terms of the 50% renewal time of the conservative species within each of eight segments, which are selected by considering the geographical features and proximity to tidal inlets and rivers. The flushing results indicate that tide is the most dominant flushing mechanism, while river and salinity are important flushing mechanisms for segments that are far from the tidal inlets. The normalized flushing times, defined as the 50% renewal time divided by the volume of the segment, are calculated for the eight segments and compared with each other. Comparing the “normalized” flushing time at all segments, a relative flushing ranking (RFR) is generated that ranks the “normalized” flushing time from the shortest to the longest as follows: segment 2 (includes St. Sebastian), segment 8 (near Ponce Inlet), segment 3 (includes Fort Matanzas), segment 7 (near Ponce Inlet), segment 1 (includes Pine Island), segment 4 (includes Pellicer Creek), segment 6 (includes High Bridge Road), and segment 5 (includes Bings Landing). This quantitative ranking of flushing characteristics inside the GTM is made possible because of the use of a three-dimensional numerical circulation and transport model that incorporates the effect of hydrodynamics on flushing. These results provide much more quantitative information than the simple empirical residence time indices (1–4) developed for the GTM in a previous study. CH3D was also applied to simulate the circulation during January 25 to February 3, 2006. Simulated currents inside the St. Augustine Inlet on February 2, 2006, compare favorably with the currents measured by Acoustic Doppler Current Profiler (ADCP). Model simulated flow rates through St. Augustine and Matanzas inlets reproduced measured data on July 1 and June 16, 2004, respectively. Model-simulated currents and water levels improved when the flooding-and-drying version of the model was used. The three-dimensional modeling approach can be used to provide sguidance on resource management and the development of sampling strategies for several ongoing and prospective biogeochemical studies in the GTM.

Toward the Probabilistic Simulation of Storm Surge and Inundation in a Limited-Resource Environment

Abstract To create more useful storm surge and inundation forecast products, probabilistic elements are being incorporated. To achieve the highest levels of confidence in these products, it is essential that as many simulations as possible are performed during the limited amount of time available. This paper develops a framework by which probabilistic storm surge and inundation forecasts within the Curvilinear Hydrodynamics in 3D (CH3D) Storm Surge Modeling System and the Southeastern Universities Research Association Coastal Ocean Observing and Prediction Program’s forecasting systems are initiated with specific focus on the application of these methods in a limited-resource environment. Ensemble sets are created by dividing probability density functions (PDFs) of the National Hurricane Center model forecast error into bins, which are then grouped into priority levels (PLs) such that each subsequent level relies on results computed earlier and has an increasing confidence associated with it. The PDFs are...

A Real-Time Forecasting System for Hurricane Induced Storm Surge and Coastal Flooding

Hurricanes cause property damages and loss of lives in the U.S. every year. In 2004, four major hurricanes caused more than 5 billion dollars in damage each in Florida alone. Katrina in 2005 caused more than

Toward High-Resolution, Rapid, Probabilistic Forecasting of the Inundation Threat from Landfalling Hurricanes

200 billion dollars in damage. Major damage caused by a hurricane is usually associated with storm surge and coastal flooding. This paper presents CH3D-SSMS, a robust storm surge and coastal flooding forecasting system for tropical and extratropical storms. The basic forecasting system couples a storm surge and coastal flooding model (CH3D) with a shallow water wave model (SWAN) in a high resolution (50–500m) coastal/estuary/inland model grid. The coupled surge-wave model receives open boundary conditions of surge and wave from a global surge model (ADCIRC) and a global wave model (WAVEWATCH-III) which cover the Gulf of Mexico and Western Atlantic. Currently high resolution grids have been set up for the East Florida Coast (including St. Johns River, Indian River Lagoon, and adjacent coastal water), Tampa Bay and Charlotte Harbor, Florida Panhandle, and Chesapeake Bay and adjacent coastal waters. The forecast wind and atmospheric pressure information are provided by a number of NOAA wind models including NAM (North Atlantic Mesoscale), GFDL-Hurricane model, and an analytic model which uses GFDL hurricane parameters. Based on the forecast wind, the CH3D-SSMS produces an 84-hour forecast of water level, wave height/period/direction, flow field, and maximum of maximum (MOM) water level and inundation, every 6 hours. Prior to forecasting, the model performs a 24-hour nowcast using analysis wind. Performance of the CH3D-SSMS forecasting system has been demonstrated using results from 2003 (Isabel) and 2004 (Frances and Ivan) hurricanes. Forecasting of the impact of Hurricane Wilma on the Charlotte Harbor region is illustrated to reflect the current capabilities and weaknesses of the CH3D-SSMS as well as hurricane wind model. To improve the forecasting system, more accurate and efficient hurricane wind models and coupling of models of various processes and scales are needed. Hurricane-ground interaction should be incorporated into the hurricane wind model to produce more realistic near ground wind after hurricane landfall. Cyberinfrastructure should also be employed to facilitate regional and community collaboration.

A Regional Testbed for Storm Surge and Coastal Inundation Models - An Overview

AbstractState-of-the-art coupled hydrodynamic and wave models can predict the inundation threat from an approaching hurricane with high resolution and accuracy. However, these models are not highly efficient and often cannot be run sufficiently fast to provide results 2 h prior to advisory issuance within a 6-h forecast cycle. Therefore, to produce a timely inundation forecast, coarser grid models, without wave setup contributions, are typically used, which sacrifices resolution and physics. This paper introduces an efficient forecast method by applying a multidimensional interpolation technique to a predefined optimal storm database to generate the surge response for any storm based on its landfall characteristics. This technique, which provides a “digital lookup table” to predict the inundation throughout the region, is applied to the southwest Florida coast for Hurricanes Charley (2004) and Wilma (2005) and compares well with deterministic results but is obtained in a fraction of the time. Because of t...

Integrated-Process and Integrated-Scale Modeling of Large Coastal and Estuarine Areas

Since 2008, a Regional Testbed has been comparing storm surge models in terms of historical storm simulations and coastal inundation maps, e.g., Flood Insurance Rate Maps and Surge Atlas. The models include two structured grid (CH3D and POM) and two unstructured grid (ADCIRC and FVCOM) models. During 2008, the storm surge and coastal inundation in the Chesapeake Bay and the Outer Banks of North Carolina during Hurricane Isabel was simulated and the results compared in an independent but non-interoperable effort by partners. In 2009-2010, an additional model SLOSH was added, and all five models were used to simulate the storm surge and coastal inundation in southwest Florida during Hurricane Charley and the results compared. Model inputs and outputs were designed in an interoperable fashion, using common model input data, parameterization and coefficients, common model output formats using a common model data grid. Thirty scenarios were developed to test the sensitivity of the models to bathymetry, storm forcing, wind drag coefficient, bottom friction, Coriolis, 2D vs. 3D formulation, etc. Various types of model products, including time series of storm surge and maximum inundation over the entire model domain, were compared to each other and measured data. The detailed model simulations and comparisons required considerable computational and analysis time, but resulted in the discovery of how model features affected the model accuracy, leading to an overall improvement of all the models used. Testbed results showed differences in storm surge elevation and coastal inundation during both Isabel and Charley. While the simulated water level at the observed stations generally did not differ by more than 20% and no model appears to be consistently superior / inferior to any other model, there are more significant differences in the produced inundation maps. The computational efficiency differs considerably among the various models. Additional simulations of a large number (20+) of storms and domains are needed to better define the relative importance of different model parameters and to sort out the causes for subtle differences among the model results. More in-depth model inter comparison results will be forthcoming in a future paper.

Simulation of storm surge, wave, currents, and inundation in the Outer Banks and Chesapeake Bay during Hurricane Isabel in 2003: The importance of waves

To predict the response of coastal and estuarine ecosystems to anthropogenic and natural changes, it is necessary to conduct integrated-process and integrated-scale modeling of large coastal and estuarine areas. This paper presents an integrated modeling system, CH3D-IMS, which includes models of circulation, wave, particle trajectory, sediment transport, water quality dynamics, light attenuation, and seagrass dynamics. The CH3D-IMS has been and continues to be validated with data from various estuaries in Florida. A 3-D variable-density groundwater flow model and a fishery model are being coupled to the CH3D-IMS. This paper presents example applications of the CH3D-IMS including: (1) simulation of the Indian River Lagoon and trajectory of Shuttle Columbia debris in North and Central Florida Atlantic Coastal water; (2) simulation of storm surge in Tampa Bay, Sarasota Bay and adjacent Gulf of Mexico; and (3) simulation of circulation in Charlotte Harbor and adjacent Gulf of Mexico water. As the integrated modeling system continues to be applied to ever more complex problems over increasingly larger coastal areas, it requires more computational resources and disciplinary expertise which are often unavailable in any single institution. To facilitate integrated-process and integrated-scale modeling by multiple institutions, the development of an infrastructure, a regional modeling “grid” is proposed.