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Wendell A. Nuss
,
John ML Bane
,
William T. Thompson
,
Teddy Holt
,
Clive E. Dorman
,
F. Martin Ralph
,
Richard Rotunno
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Joseph B. Klemp
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William C. Skamarock
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Roger M. Samelson
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Audrey M. Rogerson
,
Chris Reason
, and
Peter Jackson

Coastally trapped wind reversals along the U.S. west coast, which are often accompanied by a northward surge of fog or stratus, are an important warm-season forecast problem due to their impact on coastal maritime activities and airport operations. Previous studies identified several possible dynamic mechanisms that could be responsible for producing these events, yet observational and modeling limitations at the time left these competing interpretations open for debate. In an effort to improve our physical understanding, and ultimately the prediction, of these events, the Office of Naval Research sponsored an Accelerated Research Initiative in Coastal Meteorology during the years 1993–98 to study these and other related coastal meteorological phenomena. This effort included two field programs to study coastally trapped disturbances as well as numerous modeling studies to explore key dynamic mechanisms. This paper describes the various efforts that occurred under this program to provide an advancement in our understanding of these disturbances. While not all issues have been solved, the synoptic and mesoscale aspects of these events are considerably better understood.

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Manuela Lehner
,
C. David Whiteman
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Sebastian W. Hoch
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Erik T. Crosman
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Matthew E. Jeglum
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Nihanth W. Cherukuru
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Ronald Calhoun
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Bianca Adler
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Norbert Kalthoff
,
Richard Rotunno
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Thomas W. Horst
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Steven Semmer
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William O. J. Brown
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Steven P. Oncley
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Roland Vogt
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A. Martina Grudzielanek
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Jan Cermak
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Nils J. Fonteyne
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Christian Bernhofer
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Andrea Pitacco
, and
Petra Klein

Abstract

The second Meteor Crater Experiment (METCRAX II) was conducted in October 2013 at Arizona’s Meteor Crater. The experiment was designed to investigate nighttime downslope windstorm−type flows that form regularly above the inner southwest sidewall of the 1.2-km diameter crater as a southwesterly mesoscale katabatic flow cascades over the crater rim. The objective of METCRAX II is to determine the causes of these strong, intermittent, and turbulent inflows that bring warm-air intrusions into the southwest part of the crater. This article provides an overview of the scientific goals of the experiment; summarizes the measurements, the crater topography, and the synoptic meteorology of the study period; and presents initial analysis results.

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Richard Rotunno
,
Leonard J. Pietrafesa
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John S. Allen
,
Bradley R. Colman
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Clive M. Dorman
,
Carl W. Kreitzberg
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Stephen J. Lord
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Miles G. McPhee
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George L. Mellor
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Christopher N. K. Mooers
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Pearn P. Niiler
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Roger A. Pielke Sr.
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Mark D. Powell
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David P. Rogers
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James D. Smith
, and
Lian Xie

U.S. Weather Research Program (USWRP) prospectus development teams (PDTs) are small groups of scientists that are convened by the USWRP lead scientist on a one-time basis to discuss critical issues and to provide advice related to future directions of the program. PDTs are a principal source of information for the Science Advisory Committee, which is a standing committee charged with the duty of making recommendations to the Program Office based upon overall program objectives. PDT-1 focused on theoretical issues, and PDT-2 on observational issues; PDT-3 is the first of several to focus on more specialized topics. PDT-3 was convened to identify forecasting problems related to U.S. coastal weather and oceanic conditions, and to suggest likely solution strategies.

There were several overriding themes that emerged from the discussion. First, the lack of data in and over critical regions of the ocean, particularly in the atmospheric boundary layer, and the upper-ocean mixed layer were identified as major impediments to coastal weather prediction. Strategies for data collection and dissemination, as well as new instrument implementation, were discussed. Second, fundamental knowledge of air–sea fluxes and boundary layer structure in situations where there is significant mesoscale variability in the atmosphere and ocean is needed. Companion field studies and numerical prediction experiments were discussed. Third, research prognostic models suggest that future operational forecast models pertaining to coastal weather will be high resolution and site specific, and will properly treat effects of local coastal geography, orography, and ocean state. The view was expressed that the exploration of coupled air-sea models of the coastal zone would be a particularly fruitful area of research. PDT-3 felt that forecasts of land-impacting tropical cyclones, Great Lakes-affected weather, and coastal cyclogenesis, in particular, would benefit from such coordinated modeling and field efforts. Fourth, forecasting for Arctic coastal zones is limited by our understanding of how sea ice forms. The importance of understanding air-sea fluxes and boundary layers in the presence of ice formation was discussed. Finally, coastal flash flood forecasting via hydrologic models is limited by the present accuracy of measured and predicted precipitation and storm surge events. Strategies for better ways to improve the latter were discussed.

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P. Drobinski
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V. Ducrocq
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P. Alpert
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E. Anagnostou
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K. Béranger
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M. Borga
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I. Braud
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A. Chanzy
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S. Davolio
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G. Delrieu
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C. Estournel
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N. Filali Boubrahmi
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J. Font
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V. Grubišić
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S. Gualdi
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V. Homar
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B. Ivančan-Picek
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C. Kottmeier
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V. Kotroni
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K. Lagouvardos
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P. Lionello
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M. C. Llasat
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W. Ludwig
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C. Lutoff
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A. Mariotti
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E. Richard
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R. Romero
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R. Rotunno
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O. Roussot
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I. Ruin
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S. Somot
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I. Taupier-Letage
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J. Tintore
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R. Uijlenhoet
, and
H. Wernli

The Mediterranean countries are experiencing important challenges related to the water cycle, including water shortages and floods, extreme winds, and ice/snow storms, that impact critically the socioeconomic vitality in the area (causing damage to property, threatening lives, affecting the energy and transportation sectors, etc.). There are gaps in our understanding of the Mediterranean water cycle and its dynamics that include the variability of the Mediterranean Sea water budget and its feedback on the variability of the continental precipitation through air–sea interactions, the impact of precipitation variability on aquifer recharge, river discharge, and soil water content and vegetation characteristics specific to the Mediterranean basin and the mechanisms that control the location and intensity of heavy precipitating systems that often produce floods. The Hydrological Cycle in Mediterranean Experiment (HyMeX) program is a 10-yr concerted experimental effort at the international level that aims to advance the scientific knowledge of the water cycle variability in all compartments (land, sea, and atmosphere) and at various time and spatial scales. It also aims to improve the processes-based models needed for forecasting hydrometeorological extremes and the models of the regional climate system for predicting regional climate variability and evolution. Finally, it aims to assess the social and economic vulnerability to hydrometeorological natural hazards in the Mediterranean and the adaptation capacity of the territories and populations therein to provide support to policy makers to cope with water-related problems under the influence of climate change, by linking scientific outcomes with related policy requirements.

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