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  • Author or Editor: Xiaolan L. Wang x
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Urs Neu
,
Mirseid G. Akperov
,
Nina Bellenbaum
,
Rasmus Benestad
,
Richard Blender
,
Rodrigo Caballero
,
Angela Cocozza
,
Helen F. Dacre
,
Yang Feng
,
Klaus Fraedrich
,
Jens Grieger
,
Sergey Gulev
,
John Hanley
,
Tim Hewson
,
Masaru Inatsu
,
Kevin Keay
,
Sarah F. Kew
,
Ina Kindem
,
Gregor C. Leckebusch
,
Margarida L. R. Liberato
,
Piero Lionello
,
Igor I. Mokhov
,
Joaquim G. Pinto
,
Christoph C. Raible
,
Marco Reale
,
Irina Rudeva
,
Mareike Schuster
,
Ian Simmonds
,
Mark Sinclair
,
Michael Sprenger
,
Natalia D. Tilinina
,
Isabel F. Trigo
,
Sven Ulbrich
,
Uwe Ulbrich
,
Xiaolan L. Wang
, and
Heini Wernli

The variability of results from different automated methods of detection and tracking of extratropical cyclones is assessed in order to identify uncertainties related to the choice of method. Fifteen international teams applied their own algorithms to the same dataset—the period 1989–2009 of interim European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERAInterim) data. This experiment is part of the community project Intercomparison of Mid Latitude Storm Diagnostics (IMILAST; see www.proclim.ch/imilast/index.html). The spread of results for cyclone frequency, intensity, life cycle, and track location is presented to illustrate the impact of using different methods. Globally, methods agree well for geographical distribution in large oceanic regions, interannual variability of cyclone numbers, geographical patterns of strong trends, and distribution shape for many life cycle characteristics. In contrast, the largest disparities exist for the total numbers of cyclones, the detection of weak cyclones, and distribution in some densely populated regions. Consistency between methods is better for strong cyclones than for shallow ones. Two case studies of relatively large, intense cyclones reveal that the identification of the most intense part of the life cycle of these events is robust between methods, but considerable differences exist during the development and the dissolution phases.

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Russell S. Vose
,
Scott Applequist
,
Mark A. Bourassa
,
Sara C. Pryor
,
Rebecca J. Barthelmie
,
Brian Blanton
,
Peter D. Bromirski
,
Harold E. Brooks
,
Arthur T. DeGaetano
,
Randall M. Dole
,
David R. Easterling
,
Robert E. Jensen
,
Thomas R. Karl
,
Richard W. Katz
,
Katherine Klink
,
Michael C. Kruk
,
Kenneth E. Kunkel
,
Michael C. MacCracken
,
Thomas C. Peterson
,
Karsten Shein
,
Bridget R. Thomas
,
John E. Walsh
,
Xiaolan L. Wang
,
Michael F. Wehner
,
Donald J. Wuebbles
, and
Robert S. Young

This scientific assessment examines changes in three climate extremes—extratropical storms, winds, and waves—with an emphasis on U.S. coastal regions during the cold season. There is moderate evidence of an increase in both extratropical storm frequency and intensity during the cold season in the Northern Hemisphere since 1950, with suggestive evidence of geographic shifts resulting in slight upward trends in offshore/coastal regions. There is also suggestive evidence of an increase in extreme winds (at least annually) over parts of the ocean since the early to mid-1980s, but the evidence over the U.S. land surface is inconclusive. Finally, there is moderate evidence of an increase in extreme waves in winter along the Pacific coast since the 1950s, but along other U.S. shorelines any tendencies are of modest magnitude compared with historical variability. The data for extratropical cyclones are considered to be of relatively high quality for trend detection, whereas the data for extreme winds and waves are judged to be of intermediate quality. In terms of physical causes leading to multidecadal changes, the level of understanding for both extratropical storms and extreme winds is considered to be relatively low, while that for extreme waves is judged to be intermediate. Since the ability to measure these changes with some confidence is relatively recent, understanding is expected to improve in the future for a variety of reasons, including increased periods of record and the development of “climate reanalysis” projects.

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