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Sophia E. Brumer
,
Christopher J. Zappa
,
Ian M. Brooks
,
Hitoshi Tamura
,
Scott M. Brown
,
Byron W. Blomquist
,
Christopher W. Fairall
, and
Alejandro Cifuentes-Lorenzen

Abstract

Concurrent wavefield and turbulent flux measurements acquired during the Southern Ocean (SO) Gas Exchange (GasEx) and the High Wind Speed Gas Exchange Study (HiWinGS) projects permit evaluation of the dependence of the whitecap coverage W on wind speed, wave age, wave steepness, mean square slope, and wind-wave and breaking Reynolds numbers. The W was determined from over 600 high-frequency visible imagery recordings of 20 min each. Wave statistics were computed from in situ and remotely sensed data as well as from a WAVEWATCH III hindcast. The first shipborne estimates of W under sustained 10-m neutral wind speeds U 10N of 25 m s−1 were obtained during HiWinGS. These measurements suggest that W levels off at high wind speed, not exceeding 10% when averaged over 20 min. Combining wind speed and wave height in the form of the wind-wave Reynolds number resulted in closely agreeing models for both datasets, individually and combined. These are also in good agreement with two previous studies. When expressing W in terms of wavefield statistics only or wave age, larger scatter is observed and/or there is little agreement between SO GasEx, HiWinGS, and previously published data. The wind speed–only parameterizations deduced from the SO GasEx and HiWinGS datasets agree closely and capture more of the observed W variability than Reynolds number parameterizations. However, these wind speed–only models do not agree as well with previous studies than the wind-wave Reynolds numbers.

Full access
Scott Sandgathe
,
Bonnie R. Brown
,
Jessie C. Carman
,
Johnna M. Infanti
,
Bradford Johnson
,
David McCarren
, and
Eileen McIlvain
Free access
Brian J. Carroll
,
W. Alan Brewer
,
Edward Strobach
,
Neil Lareau
,
Steven S. Brown
,
M. Miguel Valero
,
Adam Kochanski
,
Craig B. Clements
,
Ralph Kahn
,
Katherine T. Junghenn Noyes
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Amanda Makowiecki
,
Maxwell W. Holloway
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Michael Zucker
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Kathleen Clough
,
Jack Drucker
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Kristen Zuraski
,
Jeff Peischl
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Brandi McCarty
,
Richard Marchbanks
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Scott Sandberg
,
Sunil Baidar
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Yelena L. Pichugina
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Robert M. Banta
,
Siyuan Wang
,
Andrew Klofas
,
Braeden Winters
, and
Tyler Salas

Abstract

The social, economic, and ecological impacts of wildfires are increasing over much of the United States and globally, partially due to changing climate and build-up of fuels from past forest management practices. This creates a need to improve coupled fire–atmosphere forecast models. However, model performance is difficult to evaluate due to scarcity of observations for many key fire–atmosphere interactions, including updrafts and plume injection height, plume entrainment processes, fire intensity and rate-of-spread, and plume chemistry. Intensive observations of such fire–atmosphere interactions during active wildfires are rare due to the logistical challenges and scales involved. The California Fire Dynamics Experiment (CalFiDE) was designed to address these observational needs, using Doppler lidar, high-resolution multispectral imaging, and in situ air quality instruments on a NOAA Twin Otter research aircraft, and Doppler lidars, radar, and other instrumentation on multiple ground-based mobile platforms. Five wildfires were studied across northern California and southern Oregon over 16 flight days from 28 August to 25 September 2022, including a breadth of fire stages from large blow-up days to smoldering air quality observations. Missions were designed to optimize the observation of the spatial structure and temporal evolution of each fire from early afternoon until sunset during multiple consecutive days. The coordination of the mobile platforms enabled four-dimensional sampling strategies during CalFiDE that will improve understanding of fire–atmosphere dynamics, aiding in model development and prediction capability. Satellite observations contributed aerosol measurements and regional context. This article summarizes the scientific objectives, platforms and instruments deployed, coordinated sampling strategies, and presents first results.

Open access
Edward G. Patton
,
Thomas W. Horst
,
Peter P. Sullivan
,
Donald H. Lenschow
,
Steven P. Oncley
,
William O. J. Brown
,
Sean P. Burns
,
Alex B. Guenther
,
Andreas Held
,
Thomas Karl
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Shane D. Mayor
,
Luciana V. Rizzo
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Scott M. Spuler
,
Jielun Sun
,
Andrew A. Turnipseed
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Eugene J. Allwine
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Steven L. Edburg
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Brian K. Lamb
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Roni Avissar
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Ronald J. Calhoun
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Jan Kleissl
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William J. Massman
,
Kyaw Tha Paw U
, and
Jeffrey C. Weil

The Canopy Horizontal Array Turbulence Study (CHATS) took place in spring 2007 and is the third in the series of Horizontal Array Turbulence Study (HATS) experiments. The HATS experiments have been instrumental in testing and developing subfilterscale (SFS) models for large-eddy simulation (LES) of planetary boundary layer (PBL) turbulence. The CHATS campaign took place in a deciduous walnut orchard near Dixon, California, and was designed to examine the impacts of vegetation on SFS turbulence. Measurements were collected both prior to and following leafout to capture the impact of leaves on the turbulence, stratification, and scalar source/sink distribution. CHATS utilized crosswind arrays of fast-response instrumentation to investigate the impact of the canopy-imposed distribution of momentum extraction and scalar sources on SFS transport of momentum, energy, and three scalars. To directly test and link with PBL parameterizations of canopy-modified turbulent exchange, CHATS also included a 30-m profile tower instrumented with turbulence instrumentation, fast and slow chemical sensors, aerosol samplers, and radiation instrumentation. A highresolution scanning backscatter lidar characterized the turbulence structure above and within the canopy; a scanning Doppler lidar, mini sodar/radio acoustic sounding system (RASS), and a new helicopter-observing platform provided details of the PBL-scale flow. Ultimately, the CHATS dataset will lead to improved parameterizations of energy and scalar transport to and from vegetation, which are a critical component of global and regional land, atmosphere, and chemical models. This manuscript presents an overview of the experiment, documents the regime sampled, and highlights some preliminary key findings.

Full access
Randall M. Dole
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J. Ryan Spackman
,
Matthew Newman
,
Gilbert P. Compo
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Catherine A. Smith
,
Leslie M. Hartten
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Joseph J. Barsugli
,
Robert S. Webb
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Martin P. Hoerling
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Robert Cifelli
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Klaus Wolter
,
Christopher D. Barnet
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Maria Gehne
,
Ronald Gelaro
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George N. Kiladis
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Scott Abbott
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Elena Akish
,
John Albers
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John M. Brown
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Christopher J. Cox
,
Lisa Darby
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Gijs de Boer
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Barbara DeLuisi
,
Juliana Dias
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Jason Dunion
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Jon Eischeid
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Christopher Fairall
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Antonia Gambacorta
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Brian K. Gorton
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Andrew Hoell
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Janet Intrieri
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Darren Jackson
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Paul E. Johnston
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Richard Lataitis
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Kelly M. Mahoney
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Katherine McCaffrey
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H. Alex McColl
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Michael J. Mueller
,
Donald Murray
,
Paul J. Neiman
,
William Otto
,
Ola Persson
,
Xiao-Wei Quan
,
Imtiaz Rangwala
,
Andrea J. Ray
,
David Reynolds
,
Emily Riley Dellaripa
,
Karen Rosenlof
,
Naoko Sakaeda
,
Prashant D. Sardeshmukh
,
Laura C. Slivinski
,
Lesley Smith
,
Amy Solomon
,
Dustin Swales
,
Stefan Tulich
,
Allen White
,
Gary Wick
,
Matthew G. Winterkorn
,
Daniel E. Wolfe
, and
Robert Zamora

Abstract

Forecasts by mid-2015 for a strong El Niño during winter 2015/16 presented an exceptional scientific opportunity to accelerate advances in understanding and predictions of an extreme climate event and its impacts while the event was ongoing. Seizing this opportunity, the National Oceanic and Atmospheric Administration (NOAA) initiated an El Niño Rapid Response (ENRR), conducting the first field campaign to obtain intensive atmospheric observations over the tropical Pacific during El Niño.

The overarching ENRR goal was to determine the atmospheric response to El Niño and the implications for predicting extratropical storms and U.S. West Coast rainfall. The field campaign observations extended from the central tropical Pacific to the West Coast, with a primary focus on the initial tropical atmospheric response that links El Niño to its global impacts. NOAA deployed its Gulfstream-IV (G-IV) aircraft to obtain observations around organized tropical convection and poleward convective outflow near the heart of El Niño. Additional tropical Pacific observations were obtained by radiosondes launched from Kiritimati , Kiribati, and the NOAA ship Ronald H. Brown, and in the eastern North Pacific by the National Aeronautics and Space Administration (NASA) Global Hawk unmanned aerial system. These observations were all transmitted in real time for use in operational prediction models. An X-band radar installed in Santa Clara, California, helped characterize precipitation distributions. This suite supported an end-to-end capability extending from tropical Pacific processes to West Coast impacts. The ENRR observations were used during the event in operational predictions. They now provide an unprecedented dataset for further research to improve understanding and predictions of El Niño and its impacts.

Full access
J. K. Andersen
,
Liss M. Andreassen
,
Emily H. Baker
,
Thomas J. Ballinger
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Logan T. Berner
,
Germar H. Bernhard
,
Uma S. Bhatt
,
Jarle W. Bjerke
,
Jason E. Box
,
L. Britt
,
R. Brown
,
David Burgess
,
John Cappelen
,
Hanne H. Christiansen
,
B. Decharme
,
C. Derksen
,
D. S. Drozdov
,
Howard E. Epstein
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L. M. Farquharson
,
Sinead L. Farrell
,
Robert S. Fausto
,
Xavier Fettweis
,
Vitali E. Fioletov
,
Bruce C. Forbes
,
Gerald V. Frost
,
Sebastian Gerland
,
Scott J. Goetz
,
Jens-Uwe Grooß
,
Edward Hanna
,
Inger Hanssen-Bauer
,
Stefan Hendricks
,
Iolanda Ialongo
,
K. Isaksen
,
Bjørn Johnsen
,
L. Kaleschke
,
A. L. Kholodov
,
Seong-Joong Kim
,
Jack Kohler
,
Zachary Labe
,
Carol Ladd
,
Kaisa Lakkala
,
Mark J. Lara
,
Bryant Loomis
,
Bartłomiej Luks
,
K. Luojus
,
Matthew J. Macander
,
G. V. Malkova
,
Kenneth D. Mankoff
,
Gloria L. Manney
,
J. M. Marsh
,
Walt Meier
,
Twila A. Moon
,
Thomas Mote
,
L. Mudryk
,
F. J. Mueter
,
Rolf Müller
,
K. E. Nyland
,
Shad O’Neel
,
James E. Overland
,
Don Perovich
,
Gareth K. Phoenix
,
Martha K. Raynolds
,
C. H. Reijmer
,
Robert Ricker
,
Vladimir E. Romanovsky
,
E. A. G. Schuur
,
Martin Sharp
,
Nikolai I. Shiklomanov
,
C. J. P. P. Smeets
,
Sharon L. Smith
,
Dimitri A. Streletskiy
,
Marco Tedesco
,
Richard L. Thoman
,
J. T. Thorson
,
X. Tian-Kunze
,
Mary-Louise Timmermans
,
Hans Tømmervik
,
Mark Tschudi
,
Dirk van As
,
R. S. W. van de Wal
,
Donald A. Walker
,
John E. Walsh
,
Muyin Wang
,
Melinda Webster
,
Øyvind Winton
,
Gabriel J. Wolken
,
K. Wood
,
Bert Wouters
, and
S. Zador
Free access
Matthew L. Druckenmiller
,
Twila A. Moon
,
Richard L. Thoman
,
Thomas J. Ballinger
,
Logan T. Berner
,
Germar H. Bernhard
,
Uma S. Bhatt
,
Jarle W. Bjerke
,
Jason E. Box
,
R. Brown
,
John Cappelen
,
Hanne H. Christiansen
,
B. Decharme
,
C. Derksen
,
Dmitry Divine
,
D. S. Drozdov
,
A. Elias Chereque
,
Howard E. Epstein
,
L. M. Farquharson
,
Sinead L. Farrell
,
Robert S. Fausto
,
Xavier Fettweis
,
Vitali E. Fioletov
,
Bruce C. Forbes
,
Gerald V. Frost
,
Emily Gargulinski
,
Sebastian Gerland
,
Scott J. Goetz
,
Z. Grabinski
,
Jens-Uwe Grooß
,
Christian Haas
,
Edward Hanna
,
Inger Hanssen-Bauer
,
Stefan Hendricks
,
Robert M. Holmes
,
Iolanda Ialongo
,
K. Isaksen
,
Piyush Jain
,
Bjørn Johnsen
,
L. Kaleschke
,
A. L. Kholodov
,
Seong-Joong Kim
,
Niels J. Korsgaard
,
Zachary Labe
,
Kaisa Lakkala
,
Mark J. Lara
,
Bryant Loomis
,
K. Luojus
,
Matthew J. Macander
,
G. V. Malkova
,
Kenneth D. Mankoff
,
Gloria L. Manney
,
James W. McClelland
,
Walter N. Meier
,
Thomas Mote
,
L. Mudryk
,
Rolf Müller
,
K. E. Nyland
,
James E. Overland
,
T. Park
,
Olga Pavlova
,
Don Perovich
,
Alek Petty
,
Gareth K. Phoenix
,
Martha K. Raynolds
,
C. H. Reijmer
,
Jacqueline Richter-Menge
,
Robert Ricker
,
Vladimir E. Romanovsky
,
Lindsay Scott
,
Hazel Shapiro
,
Alexander I. Shiklomanov
,
Nikolai I. Shiklomanov
,
C. J. P. P. Smeets
,
Sharon L. Smith
,
Amber Soja
,
Robert G. M. Spencer
,
Sandy Starkweather
,
Dimitri A. Streletskiy
,
Anya Suslova
,
Tove Svendby
,
Suzanne E. Tank
,
Marco Tedesco
,
X. Tian-Kunze
,
Mary-Louise Timmermans
,
Hans Tømmervik
,
Mikhail Tretiakov
,
Mark Tschudi
,
Sofia Vakhutinsky
,
Dirk van As
,
R. S. W. van de Wal
,
Sander Veraverbeke
,
Donald A. Walker
,
John E. Walsh
,
Muyin Wang
,
Melinda Webster
,
Øyvind Winton
,
K. Wood
,
Alison York
, and
Robert Ziel
Free access