Impact of US west coastline inhomogeneity and synoptic forcing on winds, wind stress, and wind stress curl during upwelling season

TitleImpact of US west coastline inhomogeneity and synoptic forcing on winds, wind stress, and wind stress curl during upwelling season
Publication TypeJournal Article
Year of Publication2013
AuthorsDorman C.E, Mejia J.F, Koracin D.
JournalJournal of Geophysical Research-Oceans
Volume118
Pagination4036-4051
Date Published2013/09
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000326230200004
Keywordsaccuracy; atmosphere; baja-california; cape mendocino; coastal waves 1996; inhomogeneity; marine boundary-layer; model; northern california; pressure gradient; quikscat satellite; S; supercritical-flow; U; Upwelling; West Coast; wind
Abstract

Although buoy and aircraft measurements, as well as numerical simulations, have shown intense over-shelf and slope dynamics of the west coast of the United States in the summer upwelling season, satellite footprint limitations of approximately 25 km resolution have thus far precluded long term, spatially extended monitoring of the near-coastline dynamics. However, recent advancements in satellite data processing have allowed a finer footprint, of approximately 12 km resolution, to investigate further the properties of coastal winds and consequent upwelling. This improved satellite data analysis has confirmed the intense coastal winds over the shelf and slope and revealed their spatial extensions and inhomogeneities on event and multiday scales. The inhomogeneities are dominated by the along-coast pressure gradient modulated by the synoptic effects and topographical forcing of the five major capes, which also generate upwelling wind stress and curl pattern inhomogeneities. Synoptic forcing of the coastal flow was evidenced by high correlation coefficients, in excess of 0.8, between the buoy-measured pressure differences and wind speeds; wind speeds greater than 11 m s(-1) occurred only when the along-coast pressure gradient was greater than 0.8 hPa/100 km. Based on Bernoulli flow principles, the observed upper limit of the wind speed on the downwind sides of the major capes is explained by using characteristic values of atmospheric marine layer parameters. Numerical simulations at a similar resolution (12 km) as the new satellite data footprint for June 2001, completed as part of multiyear regional climate modeling efforts, were able to reproduce the main characteristics of the flow.

DOI10.1002/jgrc.20282
Short TitleJ Geophys Res-Oceans
Integrated Research Themes: 
Student Publication: 
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