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Amy Solomon
,
Julian P. McCreary Jr.
,
Richard Kleeman
, and
Barry A. Klinger

Abstract

Processes that cause decadal variability in an intermediate coupled ocean–atmosphere model of the Pacific basin, both at northern midlatitudes and in the Tropics, are studied. The model's ocean component is a variable-temperature 3½-layer system. Its atmospheric component consists of two basic parts: an empirical model, constructed from patterns obtained by the singular value decomposition (SVD) statistical technique that determines wind stress anomalies from model sea surface temperature (SST), and a simple representation of the planetary boundary layer to calculate the surface heat flux anomalies. A third part specifies stochastic wind stress forcing from observed variability. In addition, the model is specifically designed to separate tropical and extratropical interactions, such that the Tropics can force the extratropics through the atmosphere but the extratropics can only feed back to the Tropics through the ocean.

Solutions develop two types of oscillations: an ENSO-like interannual mode and a decadal mode. As in many models of ENSO, the interannual mode is driven by positive, ocean–atmosphere feedbacks near the equator, and time-delayed negative feedback is provided by off-equatorial Rossby waves. For parameter choices that amplify midlatitude coupling by 30% (ϕ o = 1.3), a self-sustained decadal oscillation develops in the North Pacific without any tropical interactions. Diagnostic analyses show that it is maintained by ocean-to-atmosphere feedbacks in the northwest and subtropical northeast Pacific, and by atmospheric teleconnections from those regions to the northeast ocean. For weaker coupling (ϕ o = 1.2), the decadal mode is damped. In this case, the mode can be sustained by atmospheric teleconnections from the Tropics associated with the interannual mode, but not by extratropical stochastic forcing. Although including stochastic forcing does generate variability at decadal timescales, a distinct decadal spectral peak only exists when the decadal mode is active.

Decadal variability is carried to the equator by variations in the transport, rather than temperature, of the North Pacific subtropical cell. These variations modulate near-equatorial SST by altering the amount of cool, thermocline water that upwells in the eastern equatorial Pacific, which in turn feeds back to the interannual mode.

Full access
Barry A. Klinger
,
Julian P. McCreary Jr.
, and
Richard Kleeman

Abstract

An earlier study showed that an atmosphere–ocean model of the Pacific develops a midlatitude oscillation that produces decadal sea surface temperature (SST) variability on the equator. The authors use the ocean component of this model to understand better how subtropical wind stress oscillations can cause such SST variability. The model ocean consists of three active layers that correspond to the mixed layer, the thermocline, and intermediate water, all lying above a motionless abyss.

For a steady wind, the model develops a subtropical cell (STC) in which northward surface Ekman transport subducts, flows equatorward within the thermocline, and returns to the surface at the equator. Analytic results predict the model's equatorial temperature, given some knowledge of the circulation and external forcing. A prescribed subtropical wind stress anomaly perturbs the strength of the STC, which in turn modifies equatorial upwelling and equatorial SST.

The transient response to a switched-on wind perturbation is used to predict the ocean response to an oscillating wind. This method correctly predicts the results of several numerical experiments, and extends these results to a wide range of forcing periods. For an oscillating wind, there is a more complicated relationship between perturbations to equatorial SST and the various branches of the STC. The thermocline-branch anomalies are generally weaker than those in the surface and equatorial-upwelling branches. Equatorial SST anomalies lead, follow, and are roughly coincident with, variations in the thermocline, surface, and upwelling branches, respectively. Thus, while recent studies have suggested using the subsurface branch variations as a predictor of tropical–subtropical interactions, the surface branch may be a better predictor.

Full access
François Ascani
,
Eric Firing
,
Julian P. McCreary
,
Peter Brandt
, and
Richard J. Greatbatch

Abstract

We perform eddy-resolving and high vertical resolution numerical simulations of the circulation in an idealized equatorial Atlantic Ocean in order to explore the formation of the deep equatorial circulation (DEC) in this basin. Unlike in previous studies, the deep equatorial intraseasonal variability (DEIV) that is believed to be the source of the DEC is generated internally by instabilities of the upper-ocean currents. Two main simulations are discussed: solution 1, configured with a rectangular basin and with wind forcing that is zonally and temporally uniform, and solution 2, with realistic coastlines and an annual cycle of wind forcing varying zonally. Somewhat surprisingly, solution 1 produces the more realistic DEC; the large, vertical-scale currents [equatorial intermediate currents (EICs)] are found over a large zonal portion of the basin, and the small, vertical-scale equatorial currents [equatorial deep jets (EDJs)] form low-frequency, quasi-resonant, baroclinic equatorial basin modes with phase propagating mostly downward, consistent with observations. This study demonstrates that both types of currents arise from the rectification of DEIV, consistent with previous theories. The authors also find that the EDJs contribute to maintaining the EICs, suggesting that the nonlinear energy transfer is more complex than previously thought. In solution 2, the DEC is unrealistically weak and less spatially coherent than in the first simulation probably because of its weaker DEIV. Using intermediate solutions, this study finds that the main reason for this weaker DEIV is the use of realistic coastlines in solution 2. It remains to be determined what needs to be modified or included to obtain a realistic DEC in the more realistic configuration.

Full access
Thomas E. Lee
,
Steven D. Miller
,
F. Joseph Turk
,
Carl Schueler
,
Richard Julian
,
Steve Deyo
,
Patrick Dills
, and
Sherwood Wang

The National Polar-orbiting Operational Environmental Satellite System (NPOESS) will feature the Visible-Infrared Imager-Radiometer Suite (VIIRS), a 22-channel imager that will contribute to nearly half of the NPOESS environmental data records. Included on VIIRS will be the Day/Night band (DNB), a visible channel designed to image the Earth and its atmosphere in all conditions ranging from bright solar illumination, to nocturnal lunar illumination, and negligible external illumination. Drawing heritage from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) instruments orbiting since the late 1960s, the DNB will be used to detect clouds at night, understand patterns of urban development based on the emissions of cities, monitor fires, and image scenes of snow and ice at the surface of the Earth. Thanks to significant engineering improvements, the DNB will produce superior capabilities to the OLS for a number of new applications.

Full access
Duane E. Waliser
,
Mitchell W. Moncrieff
,
David Burridge
,
Andreas H. Fink
,
Dave Gochis
,
B. N. Goswami
,
Bin Guan
,
Patrick Harr
,
Julian Heming
,
Huang-Hsuing Hsu
,
Christian Jakob
,
Matt Janiga
,
Richard Johnson
,
Sarah Jones
,
Peter Knippertz
,
Jose Marengo
,
Hanh Nguyen
,
Mick Pope
,
Yolande Serra
,
Chris Thorncroft
,
Matthew Wheeler
,
Robert Wood
, and
Sandra Yuter

The representation of tropical convection remains a serious challenge to the skillfulness of our weather and climate prediction systems. To address this challenge, the World Climate Research Programme (WCRP) and The Observing System Research and Predictability Experiment (THORPEX) of the World Weather Research Programme (WWRP) are conducting a joint research activity consisting of a focus period approach along with an integrated research framework tailored to exploit the vast amounts of existing observations, expanding computational resources, and the development of new, high-resolution modeling frameworks. The objective of the Year of Tropical Convection (YOTC) is to use these constructs to advance the characterization, modeling, parameterization, and prediction of multiscale tropical convection, including relevant two-way interactions between tropical and extratropical systems. This article highlights the diverse array of scientifically interesting and socially important weather and climate events associated with the WCRP–WWRP/THORPEX YOTC period of interest: May 2008–April 2010. Notable during this 2-yr period was the change from cool to warm El Niño– Southern Oscillation (ENSO) states and the associated modulation of a wide range of smaller time- and space-scale tropical convection features. This period included a near-record-setting wet North American monsoon in 2008 and a very severe monsoon drought in India in 2009. There was also a plethora of tropical wave activity, including easterly waves, the Madden–Julian oscillation, and convectively coupled equatorial wave interactions. Numerous cases of high-impact rainfall events occurred along with notable features in the tropical cyclone record. The intent of this article is to highlight these features and phenomena, and in turn promote their interrogation via theory, observations, and models in concert with the YOTC program so that improved understanding and pre- dictions of tropical convection can be afforded.

Full access
Andreas Schäfler
,
George Craig
,
Heini Wernli
,
Philippe Arbogast
,
James D. Doyle
,
Ron McTaggart-Cowan
,
John Methven
,
Gwendal Rivière
,
Felix Ament
,
Maxi Boettcher
,
Martina Bramberger
,
Quitterie Cazenave
,
Richard Cotton
,
Susanne Crewell
,
Julien Delanoë
,
Andreas Dörnbrack
,
André Ehrlich
,
Florian Ewald
,
Andreas Fix
,
Christian M. Grams
,
Suzanne L. Gray
,
Hans Grob
,
Silke Groß
,
Martin Hagen
,
Ben Harvey
,
Lutz Hirsch
,
Marek Jacob
,
Tobias Kölling
,
Heike Konow
,
Christian Lemmerz
,
Oliver Lux
,
Linus Magnusson
,
Bernhard Mayer
,
Mario Mech
,
Richard Moore
,
Jacques Pelon
,
Julian Quinting
,
Stephan Rahm
,
Markus Rapp
,
Marc Rautenhaus
,
Oliver Reitebuch
,
Carolyn A. Reynolds
,
Harald Sodemann
,
Thomas Spengler
,
Geraint Vaughan
,
Manfred Wendisch
,
Martin Wirth
,
Benjamin Witschas
,
Kevin Wolf
, and
Tobias Zinner

Abstract

The North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft, each with a sophisticated set of remote sensing and in situ instruments, and coordinated with a suite of ground-based measurements. A total of 49 research flights were performed, including, for the first time, coordinated flights of the four aircraft: the German High Altitude and Long Range Research Aircraft (HALO), the Deutsches Zentrum für Luft- und Raumfahrt (DLR) Dassault Falcon 20, the French Service des Avions Français Instrumentés pour la Recherche en Environnement (SAFIRE) Falcon 20, and the British Facility for Airborne Atmospheric Measurements (FAAM) BAe 146. The observation period from 17 September to 22 October 2016 with frequently occurring extratropical and tropical cyclones was ideal for investigating midlatitude weather over the North Atlantic. NAWDEX featured three sequences of upstream triggers of waveguide disturbances, as well as their dynamic interaction with the jet stream, subsequent development, and eventual downstream weather impact on Europe. Examples are presented to highlight the wealth of phenomena that were sampled, the comprehensive coverage, and the multifaceted nature of the measurements. This unique dataset forms the basis for future case studies and detailed evaluations of weather and climate predictions to improve our understanding of diabatic influences on Rossby waves and the downstream impacts of weather systems affecting Europe.

Full access
Francina Dominguez
,
Roy Rasmussen
,
Changhai Liu
,
Kyoko Ikeda
,
Andreas Prein
,
Adam Varble
,
Paola A. Arias
,
Julio Bacmeister
,
Maria Laura Bettolli
,
Patrick Callaghan
,
Leila M. V. Carvalho
,
Christopher L. Castro
,
Fei Chen
,
Divyansh Chug
,
Kwok Pan (Sun) Chun
,
Aiguo Dai
,
Luminita Danaila
,
Rosmeri Porfírio da Rocha
,
Ernani de Lima Nascimento
,
Erin Dougherty
,
Jimy Dudhia
,
Trude Eidhammer
,
Zhe Feng
,
Lluís Fita
,
Rong Fu
,
Julian Giles
,
Harriet Gilmour
,
Kate Halladay
,
Yongjie Huang
,
Angela Maylee Iza Wong
,
Miguel Ángel Lagos-Zúñiga
,
Charles Jones
,
Jorge Llamocca
,
Marta Llopart
,
J. Alejandro Martinez
,
J. Carlos Martinez
,
Justin R. Minder
,
Monica Morrison
,
Zachary L. Moon
,
Ye Mu
,
Richard B. Neale
,
Kelly M. Núñez Ocasio
,
Sujan Pal
,
Erin Potter
,
German Poveda
,
Franciano Puhales
,
Kristen L. Rasmussen
,
Amanda Rehbein
,
Rosimar Rios-Berrios
,
Christoforus Bayu Risanto
,
Alan Rosales
,
Lucia Scaff
,
Anton Seimon
,
Marcelo Somos-Valenzuela
,
Yang Tian
,
Peter Van Oevelen
,
Daniel Veloso-Aguila
,
Lulin Xue
, and
Timothy Schneider
Open access
Tim Li
,
Abdallah Abida
,
Laura S. Aldeco
,
Eric J. Alfaro
,
Lincoln M. Alves
,
Jorge A. Amador
,
B. Andrade
,
Julian Baez
,
M. Yu. Bardin
,
Endalkachew Bekele
,
Eric Broedel
,
Brandon Bukunt
,
Blanca Calderón
,
Jayaka D. Campbell
,
Diego A. Campos Diaz
,
Gilma Carvajal
,
Elise Chandler
,
Vincent. Y. S. Cheng
,
Chulwoon Choi
,
Leonardo A. Clarke
,
Kris Correa
,
Felipe Costa
,
A. P. Cunha
,
Mesut Demircan
,
R. Dhurmea
,
Eliecer A. Díaz
,
M. ElKharrim
,
Bantwale D. Enyew
,
Jhan C. Espinoza
,
Amin Fazl-Kazem
,
Nava Fedaeff
,
Z. Feng
,
Chris Fenimore
,
S. D. Francis
,
Karin Gleason
,
Charles “Chip” P. Guard
,
Indra Gustari
,
S. Hagos
,
Richard R. Heim Jr.
,
Rafael Hernández
,
Hugo G. Hidalgo
,
J. A. Ijampy
,
Annie C. Joseph
,
Guillaume Jumaux
,
Khadija Kabidi
,
Johannes W. Kaiser
,
Pierre-Honore Kamsu-Tamo
,
John Kennedy
,
Valentina Khan
,
Mai Van Khiem
,
Khatuna Kokosadze
,
Natalia N. Korshunova
,
Andries C. Kruger
,
Nato Kutaladze
,
L. Labbé
,
Mónika Lakatos
,
Hoang Phuc Lam
,
Mark A. Lander
,
Waldo Lavado-Casimiro
,
T. C. Lee
,
Kinson H. Y. Leung
,
Andrew D. Magee
,
Jostein Mamen
,
José A. Marengo
,
Dora Marín
,
Charlotte McBride
,
Lia Megrelidze
,
Noelia Misevicius
,
Y. Mochizuki
,
Aurel Moise
,
Jorge Molina-Carpio
,
Natali Mora
,
Awatif E. Mostafa
,
uan José Nieto
,
Lamjav Oyunjargal
,
Reynaldo Pascual Ramírez
,
Maria Asuncion Pastor Saavedra
,
Uwe Pfeifroth
,
David Phillips
,
Madhavan Rajeevan
,
Andrea M. Ramos
,
Jayashree V. Revadekar
,
Miliaritiana Robjhon
,
Ernesto Rodriguez Camino
,
Esteban Rodriguez Guisado
,
Josyane Ronchail
,
Benjamin Rösner
,
Roberto Salinas
,
Amal Sayouri
,
Carl J. Schreck III
,
Serhat Sensoy
,
A. Shimpo
,
Fatou Sima
,
Adam Smith
,
Jacqueline Spence
,
Sandra Spillane
,
Arne Spitzer
,
A. K. Srivastava
,
José L. Stella
,
Kimberly A. Stephenson
,
Tannecia S. Stephenson
,
Michael A. Taylor
,
Wassila Thiaw
,
Skie Tobin
,
Dennis Todey
,
Katja Trachte
,
Adrian R. Trotman
,
Gerard van der Schrier
,
Cedric J. Van Meerbeeck
,
Ahad Vazifeh
,
José Vicencio Veloso
,
Wei Wang
,
Fei Xin
,
Peiqun Zhang
,
Zhiwei Zhu
, and
Jonas Zucule
Free access
Peter Bissolli
,
Catherine Ganter
,
Tim Li
,
Ademe Mekonnen
,
Ahira Sánchez-Lugo
,
Eric J. Alfaro
,
Lincoln M. Alves
,
Jorge A. Amador
,
B. Andrade
,
Francisco Argeñalso
,
P. Asgarzadeh
,
Julian Baez
,
Reuben Barakiza
,
M. Yu. Bardin
,
Mikhail Bardin
,
Oliver Bochníček
,
Brandon Bukunt
,
Blanca Calderón
,
Jayaka D. Campbell
,
Elise Chandler
,
Ladislaus Chang’a
,
Vincent Y. S. Cheng
,
Leonardo A. Clarke
,
Kris Correa
,
Catalina Cortés
,
Felipe Costa
,
A.P.M.A. Cunha
,
Mesut Demircan
,
K. R. Dhurmea
,
A. Diawara
,
Sarah Diouf
,
Dashkhuu Dulamsuren
,
M. ElKharrim
,
Jhan-Carlo Espinoza
,
A. Fazl-Kazem
,
Chris Fenimore
,
Steven Fuhrman
,
Karin Gleason
,
Charles “Chip” P. Guard
,
Samson Hagos
,
Mizuki Hanafusa
,
H. R. Hasannezhad
,
Richard R. Heim Jr.
,
Hugo G. Hidalgo
,
J. A. Ijampy
,
Gyo Soon Im
,
Annie C. Joseph
,
G. Jumaux
,
K. R. Kabidi
,
P-H. Kamsu-Tamo
,
John Kennedy
,
Valentina Khan
,
Mai Van Khiem
,
Philemon King’uza
,
Natalia N. Korshunova
,
A. C. Kruger
,
Hoang Phuc Lam
,
Mark A. Lander
,
Waldo Lavado-Casimiro
,
Tsz-Cheung Lee
,
Kinson H. Y. Leung
,
Gregor Macara
,
Jostein Mamen
,
José A. Marengo
,
Charlotte McBride
,
Noelia Misevicius
,
Aurel Moise
,
Jorge Molina-Carpio
,
Natali Mora
,
Awatif E. Mostafa
,
Habiba Mtongori
,
Charles Mutai
,
O. Ndiaye
,
Juan José Nieto
,
Latifa Nyembo
,
Patricia Nying’uro
,
Xiao Pan
,
Reynaldo Pascual Ramírez
,
David Phillips
,
Brad Pugh
,
Madhavan Rajeevan
,
M. L. Rakotonirina
,
Andrea M. Ramos
,
M. Robjhon
,
Camino Rodriguez
,
Guisado Rodriguez
,
Josyane Ronchail
,
Benjamin Rösner
,
Roberto Salinas
,
Hirotaka Sato
,
Hitoshi Sato
,
Amal Sayouri
,
Joseph Sebaziga
,
Serhat Sensoy
,
Sandra Spillane
,
Katja Trachte
,
Gerard van der Schrier
,
F. Sima
,
Adam Smith
,
Jacqueline M. Spence
,
O. P. Sreejith
,
A. K. Srivastava
,
José L. Stella
,
Kimberly A. Stephenson
,
Tannecia S. Stephenson
,
S. Supari
,
Sahar Tajbakhsh-Mosalman
,
Gerard Tamar
,
Michael A. Taylor
,
Asaminew Teshome
,
Wassila M. Thiaw
,
Skie Tobin
,
Adrian R. Trotman
,
Cedric J. Van Meerbeeck
,
A. Vazifeh
,
Shunya Wakamatsu
,
Wei Wang
,
Fei Xin
,
F. Zeng
,
Peiqun Zhang
, and
Zhiwei Zhu
Free access
Peter Bissolli
,
Catherine Ganter
,
A. Mekonnen
,
Ahira Sánchez-Lugo
,
Zhiwei Zhu
,
A. Abida
,
W. Agyakwah
,
Laura S. Aldeco
,
Eric J. Alfaro
,
Lincoln. M. Alves
,
Jorge A. Amador
,
B. Andrade
,
Grinia Avalos
,
Stephan Bader
,
Julian Baez
,
M. Yu Bardin
,
E. Bekele
,
Guillem Martín Bellido
,
Christine Berne
,
A. E. Bhuiyan
,
Oliver Bochníček
,
Brandon Bukunt
,
Blanca Calderón
,
Jayaka Campbell
,
Elise Chandler
,
Hua Chen
,
Vincent Y. S. Cheng
,
Leonardo Clarke
,
Kris Correa
,
Felipe Costa
,
Lenka Crhova
,
Ana P. Cunha
,
Veerle De Bock
,
Mesut Demircan
,
Ricardo Deus
,
K. R. Dhurmea
,
S. Dirkse
,
Paula Drumond
,
Dashkhuu Dulamsuren
,
Mithat Ekici
,
M. ElKharrim
,
Jhan-Carlo Espinoza
,
Chris Fenimore
,
Chris Fogarty
,
Steven Fuhrman
,
Karin Gleason
,
Charles “Chip” P. Guard
,
S. Hagos
,
Richard R. Heim Jr.
,
Sverker Hellström
,
J. Hicks
,
Hugo G. Hidalgo
,
Hongjie Huang
,
Gerardo Jadra
,
G. Jumaux
,
K. Kabidi
,
Amin Fazl Kazemi
,
Mike Kendon
,
Kenneth Kerr
,
Valentina Khan
,
Mai Van Khiem
,
Mi Ju Kim
,
Natalia N. Korshunova
,
A. C. Kruger
,
Mónika Lakatos
,
Hoang Phuc Lam
,
Waldo Lavado-Casimiro
,
Tsz-Cheung Lee
,
Kinson H. Y. Leung
,
Tanja Likso
,
Rui Lu
,
Jostein Mamen
,
Izolda Marcinonienė
,
Jose A. Marengo
,
Mohammadi Marjan
,
Ana E. Martínez
,
C. McBride
,
Tristan Meyers
,
Noelia Misevicius
,
Aurel Moise
,
Jorge Molina-Carpio
,
Natali Mora
,
Johnny Morán
,
Claire Morehen
,
A. E. Mostafa
,
Juan J. Nieto
,
Yoshinori Oikawa
,
Yuka Okunaka
,
Reynaldo Pascual Ramírez
,
Melita Perčec Tadić
,
Vanda Pires
,
Kenny Quisbert
,
Willy R. Quispe
,
M. Rajeevan
,
Andrea M. Ramos
,
Cristina Recalde
,
Alejandra J. Reyes Kohler
,
M. Robjhon
,
Esteban Rodriguez Guisado
,
Josyane Ronchail
,
Benjamin Rösner
,
Henrieke Rösner
,
Frans Rubek
,
Roberto Salinas
,
A. Sayouri
,
Semjon Schimanke
,
Z. T. Segele
,
Serhat Sensoy
,
Amsari Mudzakir Setiawan
,
R. Shukla
,
F. Sima
,
Adam Smith
,
Jacqueline Spence-Hemmings
,
Sandra Spillane
,
O. P. Sreejith
,
A. K. Srivastava
,
Jose L. Stella
,
Tannecia S. Stephenson
,
Kiyotoshi Takahashi
,
Kazuto Takemura
,
Michael A. Taylor
,
W. M. Thiaw
,
Skie Tobin
,
Lidia Trescilo
,
Adrian Trotman
,
Gerard van der Schrier
,
Cedric J. Van Meerbeeck
,
Ahad Vazife
,
An Willems
, and
Peiqun Zhang
Open access