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CONTENTS
Volume 24, Number 6, June 2017
 

Abstract
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Key Words
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Address
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Abstract
The Santa Ana winds occur in Southern California during the September-May time frame, bringing low humidities across the area and strong winds at favored locations, which include some mountain gaps and on particular slopes. The exceptionally strong event of late October 2007, which sparked and/or spread numerous fires across the region, is compared to more recent events using a numerical model verified against a very dense, limited-area network (mesonet) that has been recently deployed in San Diego County. The focus is placed on the spatial and temporal structure of the winds within the lowest two kilometers above the ground within the mesonet, along with an attempt to gauge winds and gusts occurring during and after the onset of October 2007\'s Witch fire, which became one of the largest wildfires in California history.

Key Words
complex terrain; downslope winds; numerical weather prediction; gust forecasting

Address
Robert G. Fovell: Department of Atmospheric and Environmental Sciences, University at Albany, State University of New York, Albany, NY, USA
Yang Cao: Department of Hydrology and Atmospheric Sciences, The University of Arizona, Tucson, AZ, USA

Abstract
The meteorological model WRF is used to investigate the wind circulation in Valle Camonica, Italy, an alpine valley that includes a large subalpine lake. The aim was to obtain the information necessary to evaluate the wind potential of this area and, from a methodological point of view, to suggest how numerical modeling can be used to locate the most interesting spots for wind exploitation. Two simulations are carried out in order to analyze typical scenarios occurring in the valley. In the first one, the diurnal cycle of thermally-induced winds generated by the heating-cooling of the mountain range encircling the valley is analyzed. The results show that the mountain slopes strongly affect the low-level winds during both daytime and nighttime, and that the correct setting of the lake temperature improves the quality of the meteorological fields provided by WRF significantly. The second simulation deals with an event of strong downslope winds caused by the passage of a cold front. Comparisons between simulated and measured wind speed, direction and air temperature are also shown.

Key Words
alpine valley; complex terrain; katabatic flows; Lake Iseo; WRF

Address
Antonio Cantelli, Paolo Monti and Giovanni Leuzzi: DICEA, Università degli Studi di Roma \"La Sapienza\", Via Eudossiana 18, Roma, Italy
Giulia Valerio and Marco Pilotti: DICATAM, Università di Brescia, Via Branze 43, Brescia, Italy

Abstract
Bora is a strong, usually dry temporally and spatially transient wind that is common at the eastern Adriatic Coast and many other dynamically similar regions around the world. One of the Bora main characteristics is its gustiness, when wind velocities can reach up to five times the mean velocity. Bora often creates significant problems to traffic, structures and human life in general. In this study, Bora velocity and near-ground turbulence are studied using the results of three-level high-frequency Bora field measurements carried out on a meteorological tower near the city of Split, Croatia. These measurements are analyzed for a period from April 2010 until June 2011. This rather long period allows for making quite robust and reliable conclusions. The focus is on mean Bora velocity, turbulence intensity, Reynolds shear stress and turbulence length scale profiles, as well as on Bora velocity power spectra and thermal stratification. The results are compared with commonly used empirical laws and recommendations provided in the ESDU 85020 wind engineering standard to question its applicability to Bora. The obtained results report some interesting findings. In particular, the empirical power- and logarithmic laws proved to fit mean Bora velocity profiles well. With decreasing Bora velocity there is an increase in the power-law exponent and aerodynamic surface roughness length, and simultaneously a decrease in friction velocity. This indicates an urban-like velocity profile for smaller wind velocities and a rural-like velocity profile for larger wind velocities. Bora proved to be near-neutral thermally stratified. Turbulence intensity and lateral component of turbulence length scales agree well with ESDU 85020 for this particular terrain type. Longitudinal and vertical turbulence length scales, Reynolds shear stress and velocity power spectra differ considerably from ESDU 85020. This may have significant implications on calculations of Bora wind loads on structures.

Key Words
Bora wind; gusts; velocity profile; thermal stratification; turbulence intensity; Reynolds shear stress; turbulence length scales; velocity power spectra; field measurements

Address
Petra Lepri: Meteorological and Hydrological Service, Gric 3, 10000 Zagreb, Croatia
Zeljko Vecenaj and Branko Grisogono: Department of Geophysics, Faculty of Science, University of Zagreb,
Horvatovac 95, 10000 Zagreb, Croatia
Hrvoje Kozmar: Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lucica 5, 10000 Zagreb, Croatia




Abstract
Strong downslope windstorms often occur in the Liguria Region. This part of North-Western Italy is characterised by an almost continuous mountain range along its West-East axis consisting of Maritime Alps and Apennines, which separate the Padan Plain to the North from the Mediterranean Sea to the South. Along this mountain range many valleys occur, frequently perpendicular to the mountain range axis, where strong gap flows sometimes develop from the top of the mountains ridge to the sea. In the framework of the European projects \"Wind and Ports\" and \"Wind, Ports, and Sea\", an anemometric monitoring network made up of 15 (ultra)sonic anemometric stations and 2 LiDARs has been realised in the three main commercial ports of Liguria. Thanks to this network two investigations are herein carried out. First, the wind climatology and the main statistical parameters of one Liguria valley have been studied through the analysis of the measurements taken along a period of 4 years by the anemometer placed at its southern exit. Then, the main characteristics of two strong gap flows that occurred in two distinct valley of Liguria are examined. Both these studies focus, on the one hand, on the climatological and meteorological characterisation of the downslope wind events and, on the other hand, on their most relevant quantities that can affect wind engineering problems.

Key Words
downslope winds; Alps and Apennines; (ultra)sonic anemometric measurements; LiDAR measurements; Liguria Region

Address
Massimiliano Burlando, Marco Tizzi and Giovanni Solari: Department of Civil, Chemical, and Environmental Engineering, University of Genoa, via Montallegro 1, 16145 Genoa, Italy


Abstract
In Japan, at least 28 local winds are known by name, most of them associated with downslope windstorms and gap winds. To review these windstorms, we categorize them based largely on the atmospheric conditions and formation mechanisms, and then focus on representative examples. These representative cases include the \"Yamaji kaze\", a typical downslope windstorm, the \"Hirodo kaze\", a downslope windstorm induced by a nearby typhoon (intense tropical cyclone), and the \"Karak kaze\", a downslope wind with a clear diurnal variation. Other downslope winds such as the \"Inami kaze\" and the gap wind \"Kiyokawa

Key Words
downslope windstorm; gap wind; local wind; Yamaji-kaze; Hirodo-kaze; Karak-kaze; Kiyokawa-dashi; numerical simulation; complex terrain

Address
Hiroyuki Kusaka: Center for Computational Sciences, University of Tsukuba, 305-8577, 1-1-1 Tennodai, Tsukuba, Japan
Hironori Fudeyasu: College of Education, Yokohama National University, 240-8501, 79-2 Tokiwadai, Hodogaya-ku, Yokohama, Japan


Abstract
This paper discusses some features and conditions that characterize the Zonda wind, focusing particularly on the implications for wind engineering applications. This kind of wind, typical of mountainous regions, is far from being adequately characterized for computational simulations and proper modeling in experimental facilities such as boundary layer wind tunnels. The objective of this article is to report the research works that are being developed on this kind of wind, describing the main obtained results, and also to establish some general guidelines for the proper analysis of the Zonda in the wind engineering context. A classification for the Zonda wind is indicated and different cases of structural and environmental effects are described. Available meteorological data is analyzed from the wind engineering point of view to obtain the Zonda wind gust factors, as well as basic wind speeds relevant for structural design. Some considerations and possible directions for the Zonda wind-tunnel and computational modeling are provided. Gust factor values larger than those used for open terrain were obtained, nevertheless, the basic wind speed values obtained are similar to values presented by the Argentinian Wind Code for three-second gust, principally at Mendoza airport.

Key Words
Zonda wind characteristics; katabatic wind; topographic effects; Zonda wind effects on structures and environment; field measurements

Address
Acir M. Loredo-Souza and Matthew B. Vallis1: Laboratorio de Aerodinamica das Construcoes, Universidade Federal do Rio Grande do Sul, PO Box 15035, Postal Code 91501-970, Porto Alegre, Rio Grande do Sul, Brazil
Adrian R. Wittwer: Laboratorio de Aerodinamica, Facultad de Ingeniería, Universidad Nacional del Nordeste,Postal Code 3500, Resistencia, Argentina
Hugo G. Castro: Grupo de Investigacion en Mecanica de Fluidos, Instituto de Modelado e Innovación Tecnologica - CONICET,Universidad Tecnológica Nacional, Facultad Regional Resistencia, (H3500CHJ) Chaco, Argentina






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