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M. Princevac, J. C. R. Hunt, and H. J. S. Fernando

1. Introduction About 70% of the earth’s land surface is characterized by sloping topography ( Strobach 1991 ), as is the terrain of most urban areas of the world. Air circulation over complex terrain is governed by synoptic forcing driven by large-scale pressure gradients or by the thermal circulation induced by heating/cooling of uneven topography ( Whiteman 2000 ). The thermal circulation, which is the theme of this paper, consists of slope and valley flows, with upslope and upvalley winds

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M. N. Raphael

1. Introduction The Santa Ana wind is a hot, dry, foehn-type, easterly or northeasterly wind that blows from the deserts east of the Sierra Nevada to the coast of southern California ( Glickman, 2000 ). It tends to occur in winter and spring. While it is named after the pass and river valley of Santa Ana, California, it can affect much of the southern California region. The occurrence of the Santa Ana wind is anticipated each year. It is an important local, meteorological phenomenon commanding

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M. Oltmanns, F. Straneo, G. W. K. Moore, and S. H. Mernild

1. Introduction The Ammassalik region of southeast Greenland is well known for strong winds blowing off the ice sheet, which can be of hurricane intensity and cause severe destruction ( Rasmussen 1989 ; Born and Boecher 2000 ; Mernild et al. 2008 ). These winds are called “piteraqs” and the strongest was observed on 6 February 1970, with estimated wind speeds of 90 m s −1 and temperatures of −20°C ( Born and Boecher 2000 ). While similar events occur in other regions along the coast, for

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David M. Gaffin

1. Introduction Widespread reports of wind damage (large trees and power lines down) occurred in the southern Appalachian region ( Fig. 1 ) on 23 December 2004, 17 October 2006, 25 February 2007, and 1 March 2007. Especially hard hit were the western foothills of the Great Smoky Mountains National Park and the Camp Creek area in the foothills of Greene County, Tennessee ( Fig. 2 ), where numerous trees were reported down, which closed almost all roads in these areas. In addition, several homes

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Juerg Schmidli, Brian Billings, Fotini K. Chow, Stephan F. J. de Wekker, James Doyle, Vanda Grubišić, Teddy Holt, Qiangfang Jiang, Katherine A. Lundquist, Peter Sheridan, Simon Vosper, C. David Whiteman, Andrzej A. Wyszogrodzki, and Günther Zängl

1. Introduction Over mountain areas the evolution of the boundary layer is particularly complex as a result of the interaction between boundary layer turbulence and thermally induced mesoscale wind systems, such as the slope and valley winds (e.g., Rotach et al. 2008 ). As the horizontal resolution of operational forecasts progresses to finer resolution, a larger spectrum of thermally induced wind systems can be explicitly resolved. It is therefore useful to document the current state

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Daniel F. Steinhoff, David H. Bromwich, Michelle Lambertson, Shelley L. Knuth, and Matthew A. Lazzara

1. Introduction During 15–16 May 2004, a severe windstorm struck McMurdo Station, Antarctica. Official observations are lacking because the anemometer was blown away; however, observations from McMurdo Building 71 recorded a maximum wind speed of 71.5 m s −1 and sustained wind speeds of 35–50 m s −1 between 1800 UTC 15 May and 0000 UTC 16 May ( Dalrymple 2004 ). Observations from nearby Arrival Heights and Black Island recorded maximum speeds of 84 and 64 m s −1 , respectively, and sustained

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Michael A. Spall and Joseph Pedlosky

shelf and the open ocean is important and dynamically interesting because it is generally marked by a rapid change in bottom depth at the shelf break. Because flow tends to be along constant depth contours, the shelf break provides a strong barrier to exchange. There are many mechanisms that may lead to exchange across the shelf break, including wind forcing, eddy fluxes, filamenting and small-scale mixing, dense bottom plumes, and transport in the bottom boundary layer. We focus here on one

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Ákos Horváth, Olivier Hautecoeur, Régis Borde, Hartwig Deneke, and Stefan A. Buehler

combination with Earth’s rotation over 50 min produces a minimum imagery overlap between the tandem of approximately one-half of a swath at low latitudes. Atmospheric motion vectors (AMVs)—hereinafter also referred to as “winds” although they are only a proxy measure of air motion—are derived day and night by tracking clouds in 10.8- μ m infrared (IR) images, utilizing either the swath overlap between consecutive orbits of one of the MetOp satellites or that between the pair. EUMETSAT provides three

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Kristopher B. Karnauskas, Antonio J. Busalacchi, and Raghu Murtugudde

orographic interaction with the Isthmuses of Tehuantepec and Papagayo, form intense low-level wind jets over the east Pacific warm pool (e.g., Hurd 1929 ; Clarke 1988 ; Schultz et al. 1997 , 1998 ; Fig. 1 ). These wind jets have long been known to the shipping and fishing industries, as well as recreational boaters, many of whom can recall encounters with “Tehuantepecers,” or gale-force winds near the Gulf of Tehuantepec that seem to “come out of nowhere.” Tehuantepec gap wind events have been

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Olivier Hautecoeur and Régis Borde

1. Introduction Atmospheric motion vectors (AMVs) are derived from satellites by tracking clouds or water vapor features in consecutive satellite images. Because they constitute the only upper-level wind observations with good global coverage for the tropics, midlatitudes, and polar areas, especially over the large oceanic areas, the AMVs are continuously assimilated into numerical weather prediction (NWP) models to improve the forecast score. AMVs are extracted routinely by a number of

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