Showing papers by "Naval Postgraduate School published in 2003"

The extratropical transition of tropical cyclones : forecast challenges, current understanding, and future directions

Abstract: A significant number of tropical cyclones move into the midlatitudes and transform into extratropical cyclones. This process is generally referred to as extratropical transition (ET). During ET a cyclone frequently produces intense rainfall and strong winds and has increased forward motion, so that such systems pose a serious threat to land and maritime activities. Changes in the structure of a system as it evolves from a tropical to an extratropical cyclone during ET necessitate changes in forecast strategies. In this paper a brief climatology of ET is given and the challenges associated with forecasting extratropical transition are described in terms of the forecast variables (track, intensity, surface winds, precipitation) and their impacts (flooding, bush fires, ocean response). The problems associated with the numerical prediction of ET are discussed. A comprehensive review of the current understanding of the processes involved in ET is presented. Classifications of extratropical transition ...

A User's Guide to the Brave New World of Designing Simulation Experiments

Abstract: The article of record as published may be located at http://dx.doi.org/10.1287/ijoc.1050.0136

Islamic Political Identity in Turkey

Abstract: In November of 2002, the Justice and Development Party swept to victory in the Turkish parliamentary elections. Because of the party's Islamic roots, its electoral triumph has sparked a host of questions both in Turkey and in the West: Does the party harbor a secret Islamist agenda? Will the new government seek to overturn nearly a century of secularization stemming from Kemal Ataturk's early-twentieth-century reforms? Most fundamentally, is Islam compatible with democracy? In this penetrating work, M. Hakan Yavuz seeks to answer these questions, and to provide a comprehensive analysis of Islamic political identity in Turkey. He begins in the early twentieth century, when Kemal Ataturk led Turkey through a process of rapid secularization and crushed Islamic opposition to his authoritarian rule. Yavuz argues that since Ataturk's death in 1938, however, Turkey has been gradually moving away from his militant secularism and experiencing "a quiet Muslim reformation." Islamic political identity is not homogeneous, says Yavuz, but can be modern and progressive as well as conservative and potentially authoritarian. While the West has traditionally seen Kemalism as an engine for reform against "reactionary" political Islam, in fact the Kemalist establishment has traditionally used the "Islamic threat" as an excuse to avoid democratization and thus hold on to power. Yavuz offers an account of the "soft coup" of 1997, in which the Kemalist military-bureaucratic establishment overthrew the democratically elected coalition government, which was led by the pro-Islamic Refah party. He argues that the soft coup plunged Turkey into a renewed legitimacy crisis which can only be resolved by the liberalization of the political system. The book ends with a discussion of the most recent election and its implications for Turkey and the Muslim world. Yavuz argues that Islamic social movements can be important agents for promoting a democratic and pluralistic society, and that the Turkish example holds long term promise for the rest of the Muslim world. Based on extensive fieldwork and interviews, this work offers a sophisticated new understanding of the role of political Islam in one of the world's most strategically important countries.

Mesoscale eddies in the South China Sea observed with altimeter data

Abstract: [1] A composite time series (1993–2000) of sea surface height anomaly from several satellites is used to identify eddies in the South China Sea (SCS). The eddy lifetime, radius, strength, and straight-line travel distance are estimated. Altogether 58 anticyclonic eddies and 28 cyclonic eddies are identified for this period. They are grouped into four geographical zones according to known eddy generation mechanisms, and their statistics are discussed accordingly. Our geographical classification is a useful first step in gaining an overview of their generation.

A Theory for the Indian Ocean Dipole–Zonal Mode*

Abstract: Four fundamental differences of air–sea interactions between the tropical Pacific and Indian Oceans are identified based on observational analyses and physical reasoning. The first difference is represented by the strong contrast of a zonal cloud–SST phase relationship between the warm and cool oceans. The in-phase cloud–SST relationship in the warm oceans leads to a strong negative feedback, while a significant phase difference in the cold tongue leads to a much weaker thermodynamic damping. The second difference arises from the reversal of the basic-state zonal wind and the tilting of the ocean thermocline, which leads to distinctive effects of ocean waves. The third difference lies in the existence of the Asian monsoon and its interaction with the adjacent oceans. The fourth difference is that the southeast Indian Ocean is a region where a positive atmosphere–ocean thermodynamic feedback exists in boreal summer. A conceptual coupled atmosphere–ocean model was constructed aimed to understand th...

Comparison of size and morphological measurements of coarse mode dust particles from Africa

Abstract: [1] A multitude of sensitivity studies in the literature point to the importance of proper chemical and morphological characterization of particles when the radiative impacts of airborne dusts are modeled. However, the community data set is based on heterogeneous measurement methods relying on varying aerodynamic, chemical, morphological, and optical means. During the Puerto Rico Dust Experiment, size distributions of dust particles from Africa were measured using a variety of aerodynamic, optical, and geometric means. Consistent with the literature, comparisons of these size distributions showed quite dissimilar results. “Measured” volume median diameters varied from 2.5 to 9 μm for various geometric, aerodynamic, optical, and optical inversion methods. Aerodynamic systems showed mixed performance. Column integrated size distributions inverted from AERONET Sun/sky radiance data produced somewhat reasonable results in the coarse mode when given proper constraints and taken in the proper context. The largest systematic errors were found in optical particle counters due to insensitivities to particle size in the 4–10 μm region with further complications due to dust particle morphology and index of refraction issues. As these methods can produce quite dissimilar size distributions, considerable errors in calculated radiative properties can occur if incorrectly modeled into dust parameters. None of the methods compared in this study can adequately reproduce the measured mass extinction or mass scattering efficiency of the dust using spherical geometry methods. Given all of the uncertainties in the sizing methods, we promote the use of fundamental and quantifiable descriptors of particles such as mass as a function of aerodynamic diameter.

Ekman transport and pumping in the California Current based on the U.S. Navy's high‐resolution atmospheric model (COAMPS)

Abstract: [1] Upwelling in the California Current system due to Ekman transport and pumping was estimated using a high-resolution (9-km grid) atmospheric model reanalysis. Model winds, verified with satellite-measured winds at 13 locations, had weekly averaged wind components within 1.7 m s−1 RMS, and wind gradients within 1.6 m s−1 per 100 km RMS. Model wind hind-casts from May 1999 to September 2000 revealed narrow bands (about 10 by 50 km) of strong wind stress and wind stress curl parallel to the coast and adjacent to major coastal promontories. These bands, which are sub-grid scale in operational models, were capable of generating local upwelling greater than 10 m d−1 and downwelling greater than 5 m d−1. Peak summer estimates for the California Current system indicate vertical transport due to Ekman pumping was roughly 1.0 × 10−6 m3 s−1, and Ekman transport from alongshore wind stress was about 0.5 × 10−6 m3 s−1. These estimates suggest that Ekman pumping from wind stress curl is as important as Ekman transport from alongshore winds in the California Current system.

Differences in safety climate between hospital personnel and naval aviators.

Abstract: We compared results of safety climate survey questions from health care respondents with those from naval aviation, a high-reliability organization. Separate surveys containing a subset of 23 similar questions were conducted among employees from 15 hospitals and from naval aviators from 226 squadrons. For each question a "problematic response" was defined that suggested an absence of a safety climate. Overall, the problematic response rate was 5.6% for naval aviators versus 17.5% for hospital personnel (p < .0001). The problematic response was 20.9% in high-hazard hospital domains such as emergency departments and operating rooms. Problematic response among hospital workers was up to 12 times greater than that among aviators on certain questions. Although further research on safety climate in health care is warranted, hospitals may need to make substantial changes to achieve a safety climate consistent with the status of high-reliability organizations.

Boussinesq modeling of longshore currents

Abstract: [1] A time domain Boussinesq model for nearshore hydrodynamics is improved to obtain the conservation of vertical vorticity correct to second order and extended for use on an open coast using longshore periodic boundary conditions. The model is utilized to simulate surface waves and longshore currents under laboratory and field conditions. Satisfactory agreement is found between numerical results and measurements, including root mean square wave height, mean water level, and longshore current. One striking result of the simulations is the prediction of the strong longshore current in the trough shoreward of the bar as observed during the Duck Experiment on Low-frequency and Incident-band Longshore and Across-shore Hydrodynamics field campaign. The model results give insight into the spatial and temporal variability of wave-driven longshore currents and the associated vertical vorticity field under the phase-resolving, random wave forcing with wave/current interaction. Numerical experiments are carried out to examine the response of the modeled longshore currents to the randomness of surface waves and the cross-shore distributions of bed shear stress coefficient. We find that both regular and irregular waves lead to very similar mean longshore currents, while the input of monochromatic, unidirectional waves results in much more energetic shear waves than does the input of random waves. The model results favor Whitford and Thornton's [1996] finding that the bed shear stress coefficient for the area offshore the bar is larger than that in the trough, as better agreement with the field data for both regular and irregular waves is found if such coefficients are used in the Boussinesq model.

Analysis of measurements of Saharan dust by airborne and ground-based remote sensing methods during the Puerto Rico Dust Experiment (PRIDE)

Abstract: For 26 days in mid-June and July 2000, a research group comprised of U.S. Navy, NASA, and university scientists conducted the Puerto Rico Dust Experiment (PRIDE). In this paper we give a brief overview of mean meteorological conditions during the study. We focus on findings on African dust transported into the Caribbean utilizing Navajo aircraft and AERONET Sun photometer data. During the study midvisible aerosol optical thickness (AOT) in Puerto Rico averaged 0.25, with a maximum less than 0.5 and with clean marine periods of _0.08. Dust AOTs near the coast of Africa (Cape Verde Islands and Dakar) averaged _0.4, 30% less than previous years. By analyzing dust vertical profiles in addition to supplemental meteorology and MPLNET lidar data we found that dust transport cannot be easily categorized into any particular conceptual model. Toward the end of the study period, the vertical distribution of dust was similar to the commonly assumed Saharan Air Layer (SAL) transport. During the early periods of the study, dust had the highest concentrations in the marine and convective boundary layers with only a, weak dust layer in the SAL being present, a state usually associated with wintertime transport patterns. We corroborate the findings of Maring et al. that in most cases, there was an unexpected lack of vertical stratification of dust particle size. We systematically analyze processes which may impact dust vertical distribution and determine and speculate that dust vertical distribution predominately influenced by flow patterns over Africa and differential advection couple with mixing by easterly waves and regional subsidence.

Principal-components-based display strategy for spectral imagery

Abstract: A new pseudocolor mapping strategy for use with spectral imagery is presented. This strategy is based on a principal components analysis of spectral data, and it capitalizes on the similarities between three-color human vision and high-dimensional hyperspectral datasets. The mapping is closely related to three-dimensional versions of scatter plots that are commonly used in remote sensing to visualize the data cloud. The transformation results in final images where the color assigned to each pixel is solely determined by the position within the data cloud. Materials with similar spectral characteristics are presented in similar hues, and basic classification and clustering decisions can be made by the observer. Final images tend to have large regions of desaturated pixels that make the image more readily interpretable. The data cloud is shown to be conical in nature, and materials with common spectral signatures radiate from the origin of the cone, which is not (in general) at the origin of the spectral data. A supervised method for locating the origin of the cone based on identification of clusters in the data is presented, and the effects of proper origin orientation are illustrated.

Swell Transformation across the Continental Shelf. Part I: Attenuation and Directional Broadening

Abstract: Extensive wave measurements were collected on the North Carolina–Virginia continental shelf in the autumn of 1999. Comparisons of observations and spectral refraction computations reveal strong cross-shelf decay of energetic remotely generated swell with, for one particular event, a maximum reduction in wave energy of 93% near the Virginia coastline, where the shelf is widest. These dramatic energy losses were observed in light-wind conditions when dissipation in the surface boundary layer caused by wave breaking (whitecaps) was weak and wave propagation directions were onshore with little directional spreading. These observations suggest that strong dissipation of wave energy takes place in the bottom boundary layer. The inferred dissipation is weaker for smaller-amplitude swells. For the three swell events described here, observations are reproduced well by numerical model hindcasts using a parameterization of wave friction over a movable sandy bed. Directional spectra that are narrow off the s...

A constitutive model for creep of lead-free solders undergoing strain-enhanced microstructural coarsening: A first report

Abstract: Lead-free solder joints in microelectronic applications frequently have microstructures comprising a dispersion of intermetallic particles in a Sn matrix. During thermomechanical cycling (TMC) of the solder joint, these particles undergo strain-enhanced coarsening, resulting in a continuously evolving, creep behavior. Because the extent of coarsening is dependent on the stress/strain state, which is dependent on the location within a joint, it is important that creep models used in joint-life prediction incorporate these effects. Here, an approach for incorporating the effect of in-situ second-phase particle coarsening in a dislocation-creep model applicable to lead-free solder alloys is proposed. The formulation, which can be expressed in a closed analytic form following some simplifications, incorporates the effects of both static- and strain-enhanced coarsening and accounts for the effects of inelastic-strain history and hydrostatic constraint. Predictions of coarsening based on the model agreed reasonably well with experimentally observed trends. Because of its simplicity, the microstructurally adaptive creep model proposed here can be easily incorporated in current finite-element codes for joint behavior simulation.

QuikSCAT Satellite Comparisons with Nearshore Buoy Wind Data off the U.S. West Coast

Abstract: To determine the accuracy of nearshore winds from the QuikSCAT satellite, winds from three satellite datasets (scientifically processed swath, gridded near-real-time, and gridded science datasets) were compared to those from 12 nearshore and 3 offshore U.S. West Coast buoys. Satellite observations from August 1999 to December 2000 that were within 25 km and 30 min of each buoy were used. Comparisons showed that satellite–buoy wind differences near shore were larger than those offshore. Editing the satellite data by discarding observations recorded in rain and those recorded in light winds improved the accuracy of all three datasets. After removing rain-flagged data and wind speeds less than 3 m s−1, root-mean-squared differences (satellite minus buoy) for swath data, the best of the three datasets, were 1.4 m s−1 and 37° based on 5741 nearshore comparisons. By removing winds less than 6 m s−1, these differences were reduced to 1.3 m s−1 and 26°. At the three offshore buoys, the root-mean-squared ...

Knowledge management research & practice: visions and directions

Abstract: This editorial paper outlines key directions for knowledge management research and practice. The editorial team presents the results from a small survey of academics and practitioners about the present and future of knowledge management, and the editors include their own informed views on how this journal can help promote scholarly inquiry in the field.

An improved quaternion-based Kalman filter for real-time tracking of rigid body orientation

Abstract: This paper presents an improved Kalman filter for real-time tracking of human body motions. An earlier version of the filter was presented at IROS 2001. Since then, the filter has been substantially improved. Real-time tracking of rigid body orientation is accomplished using the MARG (magnetic, angular rate, and gravity) sensors. A MARG sensor measures the three-dimensional local magnetic field, three-dimensional angular rate, and three-dimensional acceleration. A Kalman filter is designed to process measurements provided by the MARG sensors, and to produce real-time orientation represented in quaternions. There are many design decisions as related to choice of state vectors, output equations, process model, etc. The filter design presented in this paper utilizes the Gauss-Newton method for parameter optimization in conjunction with Kalman filtering. The use of the Gauss-Newton method, particularly the reduced-order implementation introduced in the paper, significantly simplifies the Kalman filter design, and reduces computational requirements.

Toward aerosol/cloud condensation nuclei (CCN) closure during CRYSTAL‐FACE

Abstract: During July 2002, measurements of cloud condensation nuclei were made in the vicinity of southwest Florida as part of the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE) field campaign These observations, at supersaturations of 02 and 085%, are presented here The performance of each of the two CCN counters was validated through laboratory calibration and an in situ intercomparison The measurements indicate that the aerosol sampled during the campaign was predominantly marine in character: the median concentrations were 233 cm-3 (at S = 02%) and 371 cm(sup -3) (at S = 085%) Three flights during the experiment differed from this general trend; the aerosol sampled during the two flights on 18 July was more continental in character, and the observations on 28 July indicate high spatial variability and periods of very high aerosol concentrations This study also includes a simplified aerosol/CCN closure analysis Aerosol size distributions were measured simultaneously with the CCN observations, and these data are used to predict a CCN concentration using Kohler theory For the purpose of this analysis, an idealized composition of pure ammonium sulfate was assumed The analysis indicates that in this case, there was good general agreement between the predicted and observed CCN concentrations: at S = 02%, N(sub predicted)/N(sub observed)= 1047 (R(sup 2)= 0911)); at S = 085%, N(sub predicted)/N(sub observed)=1201 (R(sup 2)= 0835)) The impacts of the compositional assumption and of including in-cloud data in the analysis are addressed The effect of removing the data from the 28 July flight is also examined; doing so improves the result of the closure analysis at S = 085% When omitting that atypical flight, N(sub predicted)/N(sub observed) = 1085 (R(sup 2) = 0770) at S = 085%

Typhoon Vamei: An equatorial tropical cyclone formation

Abstract: [1] Due to the diminishing Coriolis effect, the belt 300 km either side of the equator has been considered tropical cyclone-free. Typhoon Vamei, which developed near Singapore on 27 December 2001, was the first recorded tropical cyclone formation within 1.5 degrees of the equator. The development was the result of two interacting systems, a weak Borneo vortex that drifted into the southern tip of the South China Sea and remained there for four days, and a strong and persistent cold surge that created the large background cyclonic vorticity at the equator. The probability of a similar equatorial development is estimated to be once every 100–400 years.

Genetic Algorithms for the Construction of D-Optimal Designs

Abstract: Computer-generated designs are useful for situations where standard factorial, fractional factorial or response surface designs cannot be easily employed. Alphabetically-optimal designs are the most widely used type of computer-generated designs, and of these, the D-optimal (or D-efficient) class of designs is extremely popular. D-optimal designs are usually constructed by algorithms that sequentially add and delete points from a potential design by using a candidate set of points spaced over the region of interest. We present a technique to generate D-efficient designs using genetic algorithms (GA). This approach eliminates the need to explicitly consider a candidate set of experimental points and it can be used in highly constrained regions while maintaining a level of performance comparable to more traditional design construction techniques.

Turbulence, Condensation, and Liquid Water Transport in Numerically Simulated Nonprecipitating Stratocumulus Clouds.

Abstract: Condensation and turbulent liquid water transport in stratocumulus clouds involve complicated interactions between turbulence dynamics and cloud microphysical processes, and play essential roles in defining the cloud structure. This work aims at understanding this dynamical–microphysical interaction and providing information necessary for parameterizations of the ensemble mean condensation rate and turbulent fluxes of liquid water variables in a coupled turbulence–microphysics model. The approach is to simulate nonprecipitating stratocumulus clouds with a coupled large eddy simulation and an explicit bin-microphysical model, and then perform a budget analysis for four liquid water variables: mean liquid water content, turbulent liquid water flux, mean cloud droplet number concentration, and the number density flux. The results show that the turbulence contribution to the mean condensation rate comes from covariance of the integral cloud droplet radius and supersaturation, which enhances condensat...

Rapid Verification Method for the Trajectory Optimization of Reentry Vehicles

Abstract: Introduction T HE trajectory optimization of path-constrained nonlinear dynamic systems such as those arising in the guidanceand design of reentry vehicles has long been considereda difŽ cult problem.1i3 Of themany methods to solve such problems, the direct collocation method with sparse nonlinear programming (NLP) has proved to be quite effective. Because direct methods do not tie the resulting solutions to the Pontryaginmaximum principle4 (PMP), a two-step direct–indirect approach has been used successfully for Ž nding extremal solutions.5 One major drawback of the direct–indirect approach is that a signiŽ cant amount of labor is necessary to derive all of the necessary conditions including complex switching and junction conditions for state-constrainedproblems.Even with estimates of the adjoint arcs, solving the multipoint boundary-valueproblem is an elaborate task. Over the past few years, a new approach to solving complex trajectory optimizationproblems has been proposed.6i9 The Legendre pseudospectralmethod is a particularlyeffectivemethod because it providesspectrallyaccuratesolutionsfor the costatesand other covectorswithout the use of any analyticaldifferentialequationsfor the

The California Current system off Monterey, California: physical and biological coupling

Abstract: Repeated hydrobiological surveys over the period 1988–2002 perpendicular to the central California coast indicate strong coupling between physical circulation and biological production. An equatorward-flowing jet about 100–200 km from shore marked the inshore edge of the California Current (CC). This ‘‘CC Jet’’ had its highest velocities during late winter and spring. The jet divided inshore, biologicallyproductive waters from offshore, low-production waters. Mean flow in the inshore waters is poleward. However, this flow is interrupted in late spring and summer bya surfaceenhanced, equatorward-flowing, coastal upwelling jet. The upwelling jet coincides with maxima of nutrients, chlorophyll-a and primaryproduction. Annual variabilityin the inshore zone is related to (1) vertical py cnocline movements associated with geostrophic adjustments to accelerations of the California Current system, and (2) coastal upwelling. In offshore waters, the annual cycle accounted for a small fraction of the variability, indicating the dominance of eddies and meanders in this zone (J. Geophys. Res. 92 (1987) 12 947). The offshore regime was mesotrophic to oligotrophic, with a subsurface chlorophyll-a maximum above the nutricline. Considerable subduction mayoccur under the California Current jet and be an important process in the export of biogenic material to the deep sea. Published byElsevier Ltd.

Representative unit-cell models for open-cell metal foams with or without elastic filler

Abstract: Representative unit-cell models were developed for open-cell metallic foams in order to predict their effective elastic moduli and the failure strengths. Two different open-cell metallic foams were considered. One was just open-cell foam and the other was open-cell foam filled with an elastic material. The models were based on the metallic frames consisting of edges of tetrakaidecahedron. The filling material was modeled as elastic foundation to the tetrakaidecahedral frames. The frame structure of the unit-cell was analyzed using the finite element (FE) method. The failure strength was determined when the vertices of edges became plastic hinges under the assumption of elastic-perfectly-plastic material behavior of the metallic material. Both elastic modulus and failure strength were computed using a single step of FE analysis without any iterative or incremental procedure. In addition, a very small number of FEs was used. As a result, the unit-cell was computationally very efficient. In order to assess the representative unit-cell models, experiments were also conducted. The experimental data agreed very well with the predicted values of both stiffness and strength.

Ocean-to-ice heat flux at the North Pole environmental observatory

Abstract: [1] Data from drifting buoys deployed in April, 2002, as part of the North Pole Environmental Observatory project have been analysed to estimate ocean heat flux in the time period from 1 May 2002 to 11 Mar 2003. Prior to late January, the observatory remained in deep water, but subsequently drifted directly over the Yermak Plateau, a relatively shallow feature north of Svalbard. While over deep water, heat flux was dominated by storage and release of solar energy in the ocean boundary layer during summer. The most likely annual average value for 2002 was 2.6 W m−2, less than previous determinations in the western Arctic. Over Yermak Plateau, heat flux at the interface came from mixing of warmer water into the boundary layer from below. When the observatory was in water with depths less than 1200 m, the average heat flux was around 22 W m−2.

Beyond the Body of Knowledge: A Knowledge-Flow Approach to Project Management Theory and Practice:

Abstract: Much of the theory associated with project management is explicitly organized according to taxonomic bodies of knowledge (BOK). Although such BOK are conceptually simple and easily disseminated, th...

Simulations of the Extratropical Transition of Tropical Cyclones: Contributions by the Midlatitude Upper-Level Trough to Reintensification

Abstract: The extratropical cyclone development processes during the reintensification stage of an extratropical transition from a tropical cyclone (TC) are described using numerical simulations. Three control simulations without a tropical cyclone present examine the extratropical cyclogenesis associated with upper-level troughs that are characterized as weak, moderate, and strong. When no tropical cyclone is included in the simulation, the minimum surface pressures attained with the weak, moderate, and strong troughs are 1003, 991, and 977 mb, respectively. In all three cases, the low tilts northwestward with height during intensification, and the rainfall pattern and eventual occlusion are representative of classic extratropical cyclone development. The interactions of a tropical cyclone with each of the three midlatitude circulation patterns are compared with the control simulations to illustrate the contributions to the extratropical transition of the tropical cyclone. In the three trough-with-TC case...