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I. A. Renfrew
,
G. W. K. Moore
,
J. E. Kristjánsson
,
H. Ólafsson
,
S. L. Gray
,
G. N. Petersen
,
K. Bovis
,
P. R. A. Brown
,
I. Føre
,
T. Haine
,
C. Hay
,
E. A. Irvine
,
A Lawrence
,
T. Ohigashi
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S. Outten
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R. S. Pickart
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M. Shapiro
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D. Sproson
,
R. Swinbank
,
A. Woolley
, and
S. Zhang

Greenland has a major influence on the atmospheric circulation of the North Atlantic-western European region, dictating the location and strength of mesoscale weather systems around the coastal seas of Greenland and directly influencing synoptic-scale weather systems both locally and downstream over Europe. High winds associated with the local weather systems can induce large air-sea fluxes of heat, moisture, and momentum in a region that is critical to the overturning of the thermohaline circulation, and thus play a key role in controlling the coupled atmosphere-ocean climate system.

The Greenland Flow Distortion Experiment (GFDex) is investigating the role of Greenland in defining the structure and predictability of both local and downstream weather systems through a program of aircraft-based observation and numerical modeling. The GFDex observational program is centered upon an aircraft-based field campaign in February and March 2007, at the dawn of the International Polar Year. Twelve missions were flown with the Facility for Airborne Atmospheric Measurements' BAe-146, based out of the Keflavik, Iceland. These included the first aircraft-based observations of a reverse tip jet event, the first aircraft-based observations of barrier winds off of southeast Greenland, two polar mesoscale cyclones, a dramatic case of lee cyclogenesis, and several targeted observation missions into areas where additional observations were predicted to improve forecasts.

In this overview of GFDex the background, aims and objectives, and facilities and logistics are described. A summary of the campaign is provided, along with some of the highlights of the experiment.

Full access
G. Vaughan
,
J. Methven
,
D. Anderson
,
B. Antonescu
,
L. Baker
,
T. P. Baker
,
S. P. Ballard
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K. N. Bower
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P. R. A. Brown
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J. Chagnon
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T. W. Choularton
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J. Chylik
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P. J. Connolly
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P. A. Cook
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R. J. Cotton
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J. Crosier
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C. Dearden
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J. R. Dorsey
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T. H. A. Frame
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M. W. Gallagher
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M. Goodliff
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S. L. Gray
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B. J. Harvey
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P. Knippertz
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H. W. Lean
,
D. Li
,
G. Lloyd
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O. Martínez–Alvarado
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J. Nicol
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J. Norris
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E. Öström
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J. Owen
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D. J. Parker
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R. S. Plant
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I. A. Renfrew
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N. M. Roberts
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P. Rosenberg
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A. C. Rudd
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D. M. Schultz
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J. P. Taylor
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T. Trzeciak
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R. Tubbs
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A. K. Vance
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P. J. van Leeuwen
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A. Wellpott
, and
A. Woolley

Abstract

The Diabatic Influences on Mesoscale Structures in Extratropical Storms (DIAMET) project aims to improve forecasts of high-impact weather in extratropical cyclones through field measurements, high-resolution numerical modeling, and improved design of ensemble forecasting and data assimilation systems. This article introduces DIAMET and presents some of the first results. Four field campaigns were conducted by the project, one of which, in late 2011, coincided with an exceptionally stormy period marked by an unusually strong, zonal North Atlantic jet stream and a succession of severe windstorms in northwest Europe. As a result, December 2011 had the highest monthly North Atlantic Oscillation index (2.52) of any December in the last 60 years. Detailed observations of several of these storms were gathered using the U.K.’s BAe 146 research aircraft and extensive ground-based measurements. As an example of the results obtained during the campaign, observations are presented of Extratropical Cyclone Friedhelm on 8 December 2011, when surface winds with gusts exceeding 30 m s–1 crossed central Scotland, leading to widespread disruption to transportation and electricity supply. Friedhelm deepened 44 hPa in 24 h and developed a pronounced bent-back front wrapping around the storm center. The strongest winds at 850 hPa and the surface occurred in the southern quadrant of the storm, and detailed measurements showed these to be most intense in clear air between bands of showers. High-resolution ensemble forecasts from the Met Office showed similar features, with the strongest winds aligned in linear swaths between the bands, suggesting that there is potential for improved skill in forecasts of damaging winds.

Open access
Keith A. Browning
,
Alan M. Blyth
,
Peter A. Clark
,
Ulrich Corsmeier
,
Cyril J. Morcrette
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Judith L. Agnew
,
Sue P. Ballard
,
Dave Bamber
,
Christian Barthlott
,
Lindsay J. Bennett
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Karl M. Beswick
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Mark Bitter
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Karen E. Bozier
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Barbara J. Brooks
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Chris G. Collier
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Fay Davies
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Bernhard Deny
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Mark A. Dixon
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Thomas Feuerle
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Richard M. Forbes
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Catherine Gaffard
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Malcolm D. Gray
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Rolf Hankers
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Tim J. Hewison
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Norbert Kalthoff
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Samiro Khodayar
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Martin Kohler
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Christoph Kottmeier
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Stephan Kraut
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Michael Kunz
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Darcy N. Ladd
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Humphrey W. Lean
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Jürgen Lenfant
,
Zhihong Li
,
John Marsham
,
James McGregor
,
Stephan D. Mobbs
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John Nicol
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Emily Norton
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Douglas J. Parker
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Felicity Perry
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Markus Ramatschi
,
Hugo M. A. Ricketts
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Nigel M. Roberts
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Andrew Russell
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Helmut Schulz
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Elizabeth C. Slack
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Geraint Vaughan
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Joe Waight
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David P. Wareing
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Robert J. Watson
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Ann R. Webb
, and
Andreas Wieser

The Convective Storm Initiation Project (CSIP) is an international project to understand precisely where, when, and how convective clouds form and develop into showers in the mainly maritime environment of southern England. A major aim of CSIP is to compare the results of the very high resolution Met Office weather forecasting model with detailed observations of the early stages of convective clouds and to use the newly gained understanding to improve the predictions of the model.

A large array of ground-based instruments plus two instrumented aircraft, from the U.K. National Centre for Atmospheric Science (NCAS) and the German Institute for Meteorology and Climate Research (IMK), Karlsruhe, were deployed in southern England, over an area centered on the meteorological radars at Chilbolton, during the summers of 2004 and 2005. In addition to a variety of ground-based remote-sensing instruments, numerous rawinsondes were released at one- to two-hourly intervals from six closely spaced sites. The Met Office weather radar network and Meteosat satellite imagery were used to provide context for the observations made by the instruments deployed during CSIP.

This article presents an overview of the CSIP field campaign and examples from CSIP of the types of convective initiation phenomena that are typical in the United Kingdom. It shows the way in which certain kinds of observational data are able to reveal these phenomena and gives an explanation of how the analyses of data from the field campaign will be used in the development of an improved very high resolution NWP model for operational use.

Full access