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Robin Chadwick
,
Angeline G. Pendergrass
,
Lincoln Muniz Alves
, and
Aurel Moise

Abstract

Global warming is changing the intensity distribution of daily precipitation, with an increased frequency of heavy precipitation and reduced frequency of light/moderate precipitation in general circulation model (GCM) projections. Projected future CMIP5 GCM changes in regional daily precipitation distribution can be described by a combination of two idealized modes: a frequency decrease mode, representing a reduction in the frequency of precipitation at all rain rates; and a frequency shift mode, where the distribution shifts toward heavier rain rates. A decrease in daily precipitation frequency and an increase in intensity are projected in most regions, but the magnitude of change shows large regional variations. The two modes generally capture the projected shift from light/moderate to heavy rain rates but do not recreate GCM changes at the very highest and lowest rain rates. We propose a simple framework for deep convective precipitation change based on the dry static energy (DSE) budget, which provides a physical explanation of these idealized modes in regions and seasons where deep convection dominates precipitation. One possibility is that a frequency decrease mode is driven by increased convective inhibition (CIN). In this DSE framework, increased moisture under warming could influence the shape of the precipitation intensity distribution, particularly at the highest rain rates, but does not govern the overall magnitude of the shift to heavier rain rates, which is not well described by the Clausius–Clapeyron relationship. Changes in daily regional precipitation are not free to respond only to local changes (in e.g., moisture) but are also constrained by the DSE budget, particularly by DSE transport associated with the large-scale circulation.

Restricted access
Josephine R. Brown
,
Aurel F. Moise
,
Robert Colman
, and
Huqiang Zhang

Abstract

Multimodel mean projections of the Australian summer monsoon show little change in precipitation in a future warmer climate, even under the highest emission scenario. However, there is large uncertainty in this projection, with model projections ranging from around a 40% increase to a 40% decrease in summer monsoon precipitation. To understand the source of this model uncertainty, a set of 33 climate models from the Coupled Model Intercomparison Project phase 5 (CMIP5) is divided into groups based on their future precipitation projections (DRY, MID, and WET terciles). The DRY model mean has enhanced sea surface temperature (SST) warming across the equatorial Pacific, with maximum increases in precipitation in the western equatorial Pacific. The DRY model mean also has a large cold bias in present day SSTs in this region. The WET model mean has the largest warming in the central and eastern equatorial Pacific, with precipitation increases over much of Australia. These results suggest lower confidence for projections of reduced monsoon precipitation because of the influence of model SST biases on the SST warming pattern and precipitation response. The precipitation changes for the DRY and WET models are also decomposed into dynamic and thermodynamic components. The component due to spatial shifts in the location of convergence and precipitation is responsible for most of the difference between DRY and WET models. As spatial shifts in precipitation are closely associated with patterns of SST change, reducing uncertainty in model SST warming patterns will be crucial to improved projections of Australian monsoon precipitation.

Full access
Scott B. Power
,
François Delage
,
Robert Colman
, and
Aurel Moise

Abstract

Under global warming, increases in precipitation are expected at high latitudes and near major tropical convergence zones in some seasons, while decreases are expected in many subtropical and midlatitude areas in between. In many other areas there is no consensus among models on the sign of the projected change. This is often assumed to indicate that precipitation projections in these regions are highly uncertain.

Here, twenty-first century precipitation projections under the Special Report on Emissions Scenarios (SRES) A1B scenario using 24 World Climate Research Programme (WCRP)/Coupled Model Intercomparison Project phase 3 (CMIP3) climate models are examined. In areas with no consensus on the sign of projected change there are extensive subregions where the projected change is “very likely” (i.e., probability > 0.90) to be small (relative to, e.g., the size of interannual variability during the late twentieth century) or zero. The statistical significance of and interrelationships between methods used to identify model consensus on projected change in the 2007 Intergovernmental Panel on Climate Change (IPCC) report are examined, and the impact of interdependency among model projections on statistical significance is investigated. Interdependency among projections is shown to be much weaker than interdependency among simulations of climatology. The results show that there is more widespread consistency among the model projections than one might infer from the 2007 IPCC Fourth Assessment report. This discovery highlights the broader need to identify regions, variables, and phenomena that are expected to be little affected by anthropogenic climate change and to communicate this information to the wider community. This is especially important for projections of climate for the next 1–3 decades.

Full access
Roberta D’Agostino
,
Josephine R. Brown
,
Aurel Moise
,
Hanh Nguyen
,
Pedro L. Silva Dias
, and
Johann Jungclaus

Abstract

Past changes of Southern Hemisphere (SH) monsoons are less investigated than their northern counterpart because of relatively scarce paleodata. In addition, projections of SH monsoons are less robust than in the Northern Hemisphere. Here, we use an energetic framework to shed lights on the mechanisms determining SH monsoonal response to external forcing: precession change at the mid-Holocene versus future greenhouse gas increase (RCP8.5). Mechanisms explaining the monsoon response are investigated by decomposing the moisture budget in thermodynamic and dynamic components. SH monsoons weaken and contract in the multimodel mean of midHolocene simulations as a result of decreased net energy input and weakening of the dynamic component. In contrast, SH monsoons strengthen and expand in the RCP8.5 multimodel mean, as a result of increased net energy input and strengthening of the thermodynamic component. However, important regional differences on monsoonal precipitation emerge from the local response of Hadley and Walker circulations. In the midHolocene, the combined effect of Walker–Hadley changes explains the land–ocean precipitation contrast. Conversely, the increased local gross moist stability explains the increased local precipitation and net energy input under circulation weakening in RCP8.5.

Open access
Michael R. Grose
,
James S. Risbey
,
Aurel F. Moise
,
Stacey Osbrough
,
Craig Heady
,
Louise Wilson
, and
Tim Erwin

Abstract

Atmospheric circulation change is likely to be the dominant driver of multidecadal rainfall trends in the midlatitudes with climate change this century. This study examines circulation features relevant to southern Australian rainfall in January and July and explores emergent constraints suggested by the intermodel spread and their impact on the resulting rainfall projection in the CMIP5 ensemble. The authors find relationships between models’ bias and projected change for four features in July, each with suggestions for constraining forced change. The features are the strength of the subtropical jet over Australia, the frequency of blocked days in eastern Australia, the longitude of the peak blocking frequency east of Australia, and the latitude of the storm track within the polar front branch of the split jet. Rejecting models where the bias suggests either the direction or magnitude of change in the features is implausible produces a constraint on the projected rainfall reduction for southern Australia. For RCP8.5 by the end of the century the constrained projections are for a reduction of at least 5% in July (with models showing increase or little change being rejected). Rejecting these models in the January projections, with the assumption the bias affects the entire simulation, leads to a rejection of wet and dry outliers.

Full access
Josephine R. Brown
,
Scott B. Power
,
Francois P. Delage
,
Robert A. Colman
,
Aurel F. Moise
, and
Bradley F. Murphy

Abstract

Understanding how the South Pacific convergence zone (SPCZ) may change in the future requires the use of global coupled atmosphere–ocean models. It is therefore important to evaluate the ability of such models to realistically simulate the SPCZ. The simulation of the SPCZ in 24 coupled model simulations of the twentieth century is examined. The models and simulations are those used for the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC). The seasonal climatology and interannual variability of the SPCZ is evaluated using observed and model precipitation. Twenty models simulate a distinct SPCZ, while four models merge intertropical convergence zone and SPCZ precipitation. The majority of models simulate an SPCZ with an overly zonal orientation, rather than extending in a diagonal band into the southeast Pacific as observed. Two-thirds of models capture the observed meridional displacement of the SPCZ during El Niño and La Niña events. The four models that use ocean heat flux adjustments simulate a better tropical SPCZ pattern because of a better representation of the Pacific sea surface temperature pattern and absence of cold sea surface temperature biases on the equator. However, the flux-adjusted models do not show greater skill in simulating the interannual variability of the SPCZ. While a small subset of models does not adequately reproduce the climatology or variability of the SPCZ, the majority of models are able to capture the main features of SPCZ climatology and variability, and they can therefore be used with some confidence for future climate projections.

Full access
Bin Wang
,
Michela Biasutti
,
Michael P. Byrne
,
Christopher Castro
,
Chih-Pei Chang
,
Kerry Cook
,
Rong Fu
,
Alice M. Grimm
,
Kyung-Ja Ha
,
Harry Hendon
,
Akio Kitoh
,
R. Krishnan
,
June-Yi Lee
,
Jianping Li
,
Jian Liu
,
Aurel Moise
,
Salvatore Pascale
,
M. K. Roxy
,
Anji Seth
,
Chung-Hsiung Sui
,
Andrew Turner
,
Song Yang
,
Kyung-Sook Yun
,
Lixia Zhang
, and
Tianjun Zhou

Abstract

Monsoon rainfall has profound economic and societal impacts for more than two-thirds of the global population. Here we provide a review on past monsoon changes and their primary drivers, the projected future changes, and key physical processes, and discuss challenges of the present and future modeling and outlooks. Continued global warming and urbanization over the past century has already caused a significant rise in the intensity and frequency of extreme rainfall events in all monsoon regions (high confidence). Observed changes in the mean monsoon rainfall vary by region with significant decadal variations. Northern Hemisphere land monsoon rainfall as a whole declined from 1950 to 1980 and rebounded after the 1980s, due to the competing influences of internal climate variability and radiative forcing from greenhouse gases and aerosol forcing (high confidence); however, it remains a challenge to quantify their relative contributions. The CMIP6 models simulate better global monsoon intensity and precipitation over CMIP5 models, but common biases and large intermodal spreads persist. Nevertheless, there is high confidence that the frequency and intensity of monsoon extreme rainfall events will increase, alongside an increasing risk of drought over some regions. Also, land monsoon rainfall will increase in South Asia and East Asia (high confidence) and northern Africa (medium confidence), decrease in North America, and be unchanged in the Southern Hemisphere. Over the Asian–Australian monsoon region, the rainfall variability is projected to increase on daily to decadal scales. The rainy season will likely be lengthened in the Northern Hemisphere due to late retreat (especially over East Asia), but shortened in the Southern Hemisphere due to delayed onset.

Full access
Peter Bissolli
,
Catherine Ganter
,
Ademe Mekonnen
,
Ahira Sánchez-Lugo
,
Zhiwei Zhu
,
A. Abida
,
W. Agyakwah
,
Laura S. Aldeco
,
Eric J. Alfaro
,
Teddy Allen
,
Lincoln M. Alves
,
Jorge A. Amador
,
B. Andrade
,
P. Asgarzadeh
,
Grinia Avalos
,
Julian Baez
,
M. Yu. Bardin
,
E. Bekele
,
Renato Bertalanic
,
Oliver Bochníček
,
Brandon Bukunt
,
Blanca Calderón
,
Jayaka D. Campbell
,
Elise Chandler
,
Candice S Charlton
,
Vincent Y. S. Cheng
,
Leonardo A. Clarke
,
Kris Correa
,
Catalina R. Cortés Salazar
,
Felipe Costa
,
Lenka Crhová
,
Ana Paula Cunha
,
Mesut Demircan
,
K. R. Dhurmea
,
Diana A. Domínguez
,
Dashkhuu Dulamsuren
,
M. ElKharrim
,
Jhan-Carlo Espinoza
,
A. Fazl-Kezemi
,
Nava Fedaeff
,
Chris Fenimore
,
Steven Fuhrman
,
Karin Gleason
,
Charles “Chip” P. Guard
,
Samson Hagos
,
Mizuki Hanafusa
,
Richard R. Heim Jr.
,
John Kennedy
,
Sverker Hellström
,
Hugo G. Hidalgo
,
I. A. Ijampy
,
Gyo Soon Im
,
G. Jumaux
,
K. Kabidi
,
Kenneth Kerr
,
Yelena Khalatyan
,
Valentina Khan
,
Mai Van Khiem
,
Tobias Koch
,
Gerbrand Koren
,
Natalia N. Korshunova
,
A. C. Kruger
,
Mónika Lakatos
,
Jostein Mamen
,
Hoang Phuc Lam
,
Mark A. Lander
,
Waldo Lavado-Casimiro
,
Tsz-Cheung Lee
,
Kinson H. Y. Leung
,
Xuefeng Liu
,
Rui Lu
,
José A. Marengo
,
Mohammadi Marjan
,
Ana E. Martínez
,
Charlotte McBride
,
Mirek Mietus
,
Noelia Misevicius
,
Aurel Moise
,
Jorge Molina-Carpio
,
Natali Mora
,
Awatif E. Mostafa
,
O. Ndiaye
,
Juan J. Nieto
,
Kristin Olafsdottir
,
Reynaldo Pascual Ramírez
,
David Phillips
,
Amos Porat
,
Esteban Rodriguez Guisado
,
Madhavan Rajeevan
,
Andrea M. Ramos
,
Cristina Recalde Coronel
,
Alejandra J. Reyes Kohler
,
M. Robjhon
,
Josyane Ronchail
,
Roberto Salinas
,
Hirotaka Sato
,
Hitoshi Sato
,
Amal Sayouri
,
Serhat Sensoy
,
Amsari Mudzakir Setiawan
,
F. Sima
,
Adam Smith
,
Matthieu Sorel
,
Sandra Spillane
,
Jacqueline M. Spence
,
O. P. Sreejith
,
A. K. Srivastava
,
Tannecia S. Stephenson
,
Kiyotoshi Takahashi
,
Michael A. Taylor
,
Wassila M. Thiaw
,
Skie Tobin
,
Lidia Trescilo
,
Adrian R. Trotman
,
Cedric J. Van Meerbeeck
,
A. Vazifeh
,
Shunya Wakamatsu
,
M. F. Zaheer
,
F. Zeng
, and
Peiqun Zhang
Free 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