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  • Author or Editor: E. D. Cokelet x
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E. D. Cokelet

Abstract

A local, two-dimensional principal-component analysis has been applied to mesoscale winds in a region strongly influenced by topography. The principal components successfully separate axial winds over Puget Sound from cross-axial winds. Energy spectra of winter axial winds contain significant peaks at synoptic-scale periods of 1.5–5 days but also a strong peak of unknown origin at 17 days. Cross-axial winds are dominated by the land-sea breeze. Day-night asymmetries in the land-sea temperature contrast lead to diurnal modulation and energy at the semidiurnal period. The land breeze persists in winter over Puget Sound, but the sea breeze dominates a weakened land breeze in summer.

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E. D. Cokelet
,
M. L. Schall
, and
D. M. Dougherty

Abstract

A month-long circumnavigation of the Bering Sea basin in August 1991 was designed to study the basin-scale circulation. For the first time in this region vessel-mounted acoustic Doppler current profiler (ADCP) measurements provided an absolute reference for geostrophic currents. Transport in the Alaskan Stream (01/1500 db) was 24 Sv (Sv ≡ 106 m3 s−1) westward, considerably higher than the 10–15 Sv usually inferred from geostrophic calculations referred to 1500 db, but in good agreement with previous work relative to moored current meters. As previously reported, the stream separated from the Aleutian Ridge, forming an anticyclonic eddy that restricted inflow to the Bering Sea. Flow through the Aleutians varied substantially across the passes. The Kamchatka Current was traceable for 800 km until it left the Bering Sea carrying 14 Sv (0/3000 db). Eddies were detected from the clustering of centers of curvature of sequential ADCP vectors. Incompletely spanned eddies can bias transports. Counterrotating eddy pairs deflected and entrained Kamchatka Current water and transported it to the basin interior.

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Chidong Zhang
,
Gregory R. Foltz
,
Andy M. Chiodi
,
Calvin W. Mordy
,
Catherine R. Edwards
,
Christian Meinig
,
Dongxiao Zhang
,
Edoardo Mazza
,
Edward D. Cokelet
,
Eugene F. Burger
,
Francis Bringas
,
Gustavo J. Goni
,
Hristina G. Hristova
,
Hyun-Sook Kim
,
Joaquin A. Trinanes
,
Jun A. Zhang
,
Kathleen E. Bailey
,
Kevin M. O’Brien
,
Maria Morales-Caez
,
Noah Lawrence-Slavas
,
Richard Jenkins
,
Shuyi S. Chen
, and
Xingchao Chen

Abstract

On 30 September 2021, a saildrone uncrewed surface vehicle (USV) was steered into category 4 Hurricane Sam, the most intense storm of the 2021 Atlantic hurricane season. It measured significant wave heights up to 14 m (maximum wave height = 27 m) and near-surface winds exceeding 55 m s−1. This was the first time in more than seven decades of hurricane observations that in real time a USV transmitted scientific data, images, and videos of the dynamic ocean surface near a hurricane’s eyewall. The saildrone was part of a five-saildrone deployment of the NOAA 2021 Atlantic Hurricane Observations Mission. These saildrones observed the atmospheric and oceanic near-surface conditions of five other tropical storms, of which two became hurricanes. Such observations inside tropical cyclones help to advance the understanding and prediction of hurricanes, with the ultimate goal of saving lives and protecting property. The 2021 deployment pioneered a new practice of coordinating measurements by saildrones, underwater gliders, and airborne dropsondes to make simultaneous and near-collocated observations of the air–sea interface, the ocean immediately below, and the atmosphere immediately above. This experimental deployment opened the door to a new era of using remotely piloted uncrewed systems to observe one of the most extreme phenomena on Earth in a way previously impossible. This article provides an overview of this saildrone hurricane observations mission, describes how the saildrones were coordinated with other observing platforms, presents preliminary scientific results from these observations to demonstrate their potential utility and motivate further data analysis, and offers a vision of future hurricane observations using combined uncrewed platforms.

Open access