Bruce P. Hayden

Secular Variation in Atlantic Coast Extratropical Cyclones

Abstract To define spatial and temporal variations in annual cyclone frequencies, principal components were calculated from a matrix of annual frequencies for 74 grid cells covering eastern North America and the western North Atlantic and the years 1885 to 1978. The first principal component contrasts cyclone frequencies in continental versus marine areas. Since the early years of this century, there has been a trend toward increased cyclone frequency over marine areas and a decline in frequencies over the continent. This trend peaked in the 1960s. The second principal component is interpreted as an east coast cyclogenesis function. Like the first component, it exhibits a century-long secular variation with increasing coastal cyclogenesis in recent decades and a maximum in the 1950s. The first two components explain 45% of the oral variance. Higher order vectors (3rd and 4th) explained 12% of the variance and geographically depict variance in the Gulf coast and Great Lakes regions, respectively. Secular...

Coastal Marine Fauna and Marine Climates of the Americas

Geographic ranges of 968 marine species along coastal areas of the Americas, excluding the Arctic, were analysedfor co-ranges and compared with recent classifications of coastal marine and wave climates. Forty-two co-ranges and thirty-nine characteristic endpoints are reported. Many faunal boundaries correspond to those of previous studies, and thirty of the thirty-nine characteristic endpoints coincide with transition regions of the physical environment previously determined through analysis of motion fields of marine and atmospheric fluids. The hydrodynamics of the coastal marine environment give rise to the extant thermal structure of coastal waters and as such to the faunal distributional patterns exhibited. The high level of coincidence between biotic and abiotic zones of change along the coast clearly merits the use of both coastal marine fauna and the hydrodynamics of adjacent waters to establish the marine provinces of the coastal environment.

Systematic Variations in Inshore Bathymetry

To specify and characterize systematic regional variations in inshore bathymetry, the eigenvectors of 504 profiles of the U.S. Atlantic and Gulf coasts were calculated. The first three eigenvectors calculated account for over 97% of the topographic variance. The first eigenvector represents nearly linear departures from the mean; the second and third eigenvectors represent curvilinear bathymetrie variation; i.e., bar/trough morphology. The orthogonality of the linear slope and curvilinear bar/trough forms does not support the concept of a functional relationship between slope and the frequency of bars. In addition no relationship was revealed between inshore bar/trough morphology and offshore slope within nine miles (14 km) of the shoreline.

Climatology of 500 mb Cyclones and Anticyclones, 1950–85

Abstract The geographical and monthly frequencies of 500 mb cyclones and anticyclones in the National Meteorological Center analyses over the western half of the Northern Hemisphere are investigated for the period 1950–85. These cyclones and anticyclones, defined by the appearance of at least one closed (approximately) 6-dekameter contour around relatively low or high heights in the 500 mb height field, are generally observed less than ten percent of the time in any 10° by 10° latitude-longitude quadrangle, with cyclones being more numerous than anticyclones. The 500 mb cyclones are found primarily at middle and high latitudes, while anticyclones are observed most frequently over the subtropics. Cyclone frequency increases over the northern oceanic regions during summer, while anticyclone frequency increases throughout the subtropics during summer, especially over southwestern North America. Exceptions to these rules are observed; relatively high springtime 500 mb anticyclone frequency is found over the n...

Storms and Shoreline Configuration

ABSTRACT Spectral analysis of the 1962 great Atlantic coast storm penetration (overwash) along the Outer Banks of North Carolina and Fenwick Island, Maryland, reveals along-the-coast periodicities ranging in wavelength from 14 km to 15 km. Periodicities with similar wavelengths exist in long-term mean rates of change of the shoreline and storm-surge penetration line. This suggests the location and magnitude of storm deposits and storm hazards along the Atlantic coast are systematically distributed.

Season-to-Season Cyclone Frequency Prediction

Abstract Winter and summer half-year cyclone frequencies for eastern North America and the western North Atlantic were tabulated for 2.5° latitude by 5° longitude grid cells for the years 1885–1980. Correlation matrix eigenvectors were calculated for matrices of both the winter and summer data for a dependent set of years (1885–1959). The first four eigenvectors for winter are highly similar in form to their summer counterparts and are correlated with them in the time domain. These correlations permit a season-in-advance estimation of half-year cyclone frequencies. Forecast skill for independent years (1960–1980) in both winter and summer averages 75% relative to the 1885–1959 means as forecasts. The multivariate statistical forecast scheme outperforms both simple and damped persistence in addition to raw climatology. The climatological persistence from which the forecast skill results is shown to have both intermediate- and low-frequency components.

Shoreline Periodicities and Edge Waves

Spectral analysis of shoreline rate change data spanning 40 years and 122.6 km between Cape Hatteras and Cape Lookout reveals a hierarchy of longshore periodicities. The periodicities closely match wavelengths of hypothetical standing waves trapped between the offshore shoals of the two large capes. In addition, active and relic inlets and site-level beach characteristics coincide with the periodicities. We conclude that edge waves may play a significant role in determining the intensity of regional-scale processes and geomorphological responses along the Atlantic coast barrier islands.

Systematic Variations in Barrier-Island Topography

To quantify systematic topographic variations in Atlantic and Gulf coast barrier islands, we calculated eigenvectors of a matrix of 530 profiles. The first 2 eigenvectors (or profile functions) explained 64% of the topographic variance. Along-the-coast trends in the weightings on these functions indicate a regional scale organization and thus provide the basis for a quantitative classification of barrier-island forms.

Cyclone Occurrence Mapping: Equal Area or Raw Frequencies?

Abstract Meteorological data extracted from maps and charts is frequently normalized for area because grid cell size changes with latitude. Raw and area-normalized cyclone frequency data were compared. Area normalization deforms mean frequency patterns. The patterns of standard deviations about the mean are not deformed in the same way. Area normalization does not change calculated principal components or their time histories of weightings.

Shoreline Periodicities and Linear Offshore Shoals

Linear shoals off the Delmarva coast are believed to have evolved on the shoreface of Assateague Island in response to inshore processes. Analyses of shoreline rate-of-change data and the spatial distribution of the linear shoals indicate several spatial periodicities. The shoreline periodicities correspond to hypothetical standing edge waves. The linear shoals, however, do not have wavelengths consistent with either the shoreline periodicities or the edge waves. The strongest periodicity in the shoal field has an orientation parallel to relict beach ridges on Assateague Island dated ca 2,000 BP. Thus, the linear offshore shoals may have formed at a time when Assateague Island was shorter and edge waves of a different wavelength were present. Where sedimentary shorelines are strongly concave, such as the 123 km Arc between Cape Hatteras and Cape Lookout, inshore currents associated with standing edge waves seem to inhibit the development of linear shoals. Where the shoreline is convex, such as along the Delmarva coast, currents associated with standing edge waves are less prevalent and thus less likely to inhibit the development of linear shoals.