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Thomas L. Kozo

Abstract

A nonlinear, time-dependent, two-dimensional sea breeze model allowing imposition of prevailing large-scale wind conditions has been developed. The model is an extension of Estoque's model with modifications in the treatment of the continuity equation, eddy diffusivity (unstable conditions), surface heating function and the numerical scheme.

The model is applied to a cross section of the Beaufort Sea Coast using typically measured arctic conditions as input. These include u-w plane velocity vectors, isotachs of the u, v and w wind velocity components, temperature contours, surface wind vectors at varying distances from the coastline, and wind speed and direction profiles for various simulated synoptic wind directions.

The mathematical results reproduced measurements of atmospheric boundary layer turning of the wind with height (pilot balloon data), temporal surface wind vector turning and inversion height variations, while also giving evidence that sea breeze circulation could be strengthened by weak offshore (southwesterly and westerly winds) opposing synoptic winds.

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Thomas L. Kozo

Abstract

Though sea breezes are not often associated with the arctic, atmospheric environmental data collected in August 1976, 1977 and 1979 along the Beaufort Sea Coast of Alaska offer both circumstantial and direct evidence of the existence of sea breezes at 70°N latitude. To estimate total atmospheric boundary layer turning, a two-dimensional least squares technique is used to calculate a three hourly geostrophic wind (above the atmospheric boundary layer) with data from irregularly distributed surface pressure stations for simultaneous comparison to surface wind data. Results indicated the average turning of the wind from above the boundary layer to the surface was 120° on sea breeze days. Rotary spectra from time series data of surface winds measured at offshore and inshore sites have shown the horizontal extent of sea breeze influence to include at least a 20 km zone centered on the coastline. The sea breeze is largely responsible for the increased persistence of surface onshore (northeasterly and easterly) winds documented in August historical data for the Alaskan Beaufort Sea Coast.

The data base for arctic sea breeze studies has been enhanced by the discovery and development of the Prudhoe Bay oil fields (mid-sixties). Since the nearshore ocean current flow along the Alaskan Beaufort Sea Coast is primarily wind driven, a direct application to oil spill trajectories in lagoons and embayments exists.

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Thomas L. Kozo
,
William J. Stringer
, and
Lenora J. Torgerson

Abstract

Surface atmospheric pressure data from a triangular station network surrounding the Bering Strait are used to calculate hypothetical geostrophic wind velocities. Net daily Strait sea ice movement is derived from visible and infrared NOAA satellite imagery for November through May, 1974 to 1984. These historical ice-motion data and network wind-velocity data are used to develop an empirical 12-h advance forecast (nowcast) sea ice movement model with all-weather capabilities. A necessary outgrowth of this study has been the identification and classification of three modes of ice movement and two modes of ice immobilization according to their major driving forces. The first ice-movement mode is from the Chukchi to the Bering Sea requiring a minimum northeasterly geostrophic wind of 12 m s−1. The second and third modes represent ice movement from the Bering to the Chukchi Sea. Mode 2 is driven by a preexisting north-flowing ocean current that offsets weak winds from the northeast. Mode three is large movement due to a combination of southwesterly winds and north-flowing ocean current. The first immobilization mode (maximum duration one week) is an apparent balance between northerly wind stress, current stress from the south, and internal ice stresses. The second immobilization mode (least common) is due to double, solid sea ice arches forming across the Strait. These arches remained intact under strong northeasterly geostrophic winds (20–26 m s−1) and can last up to four weeks.

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Robert W. Fett
,
Stephen D. Burk
,
William T. Thompson
, and
Thomas L. Kozo

This paper describes unique environmental phenomena observed during LEADEX (Leads Experiment), a multidisciplinary investigation staged from an ice camp in the Beaufort Sea during March and April 1992. The paper focuses on phenomena observed by NOAA, DMSP, and the European ERS-1 satellites. The opening and closing of a lead is studied using the synthetic aperture radar (SAR) data aboardERS-1. With a mesoscale model, the authors examine the three-dimensional nature of meteorological phenomena and their effect on the opening and closing of leads and show that this model is extremely useful for interpreting structures evident in satellite and in situ observations along northern Alaska. Storms or wind events, which result in leads and fractured ice, also cause ice floes to rotate; the authors document this rotation with automated weather stations anchored to the floes. Finally, the authors describe unique thermal streaks that appeared over a large area of the Beaufort Sea during strong northeasterly winds and explore their nature using multichannel satellite data.

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