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# A Harmonic-Sine Series Expansion and its Application to Partitioning and Reconstruction Problems in a Limited Area

Qiu-Shi Chen
and
Ying-Hwa Kuo

## Abstract

A harmonic-sine series expansion for a function in two-dimensional space is proposed to be a sum of two parts. The harmonic part is the solution of the Laplace equation with prescribed boundary values of this function. The inner part is the function from which the harmonic part has been subtracted; thus, it has zero boundary value and can be expanded by the double Fourier sine series. By using the harmonic-sine series expansion, it is shown that only simple operations are needed to solve the Laplace, Poisson, and Helmholtz equations with a given boundary condition.

The harmonic-sine series expansion is used to solve the wind partitioning and reconstruction problems in a limited area. The internal wind is computed from the inner parts of the streamfunction and the velocity potential. The harmonic wind is the difference between the observed wind and internal wind. In a limited region, the internal wind can be dealt with in the same way as the horizontal wind on the globe. The development of the vorticity and divergence in a limited area can be diagnosed from the inner parts of the streamfunction and velocity potential, and the corresponding internal rotational and divergent wind components. As long as the inner parts of the streamfunction and velocity potential are defined, the separation of the wind field into the internal rotational, the internal divergent, and the harmonic winds becomes completely definite. The harmonic wind is not only nondivergent but also irrotational in a limited region.

In both partitioning and reconstruction problems, the key is to solve the Laplace equations of the harmonic parts with the prescribed boundary value of the harmonic wind. The solution of the harmonic parts for the key problem is not unique, but the computed harmonic wind from the harmonic parts is. Based on this characteristic, an iterative method is developed. From a real-data example, it is demonstrated that the harmonic parts of the streamfunction and velocity potential and the computed harmonic wind can be accurately determined within 15 iterations. The iteration method by using harmonic-sine series expansion is very effective in solving the partitioning and reconstruction of problems in a limited region.

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# A Consistency Condition for Wind-Field Reconstruction in a Limited Area and a Harmonic-Cosine Series Expansion

Qiu-Shi Chen
and
Ying-Hwa Kuo

## Abstract

This paper examines further the problem of deducing the wind field from vorticity and divergence over a limited area with prescribed winds at the boundary. An earlier work showed that the wind field in a limited area can be partitioned into internal divergent, internal rotational, and harmonic wind components. Because the harmonic wind is both nondivergent and irrotational, it is demonstrated in this paper that the two harmonic wind components at the boundary must satisfy a consistency condition. Based on this properly, a direct method is developed to solve two Laplace equations with the prescribed two harmonic wind components at the boundary. If the prescribed harmonic wind components at the boundary satisfy the consistency condition, the solution of the two Laplace equations must be nondivergent and irrotational. The direct method is shown to be highly accurate and efficient. If the prescribed wind at the boundary does not satisfy the consistency condition, this implies a mismatch between the interior vorticity and divergence and the prescribed winds at the boundary. This inconsistency must be removed before the wind field can be reconstructed. A method to remove this inconsistency is discussed.

A harmonic-cosine series expansion is also developed for a function over a limited area. The application of the harmonic-cosine series expansion to the wind-field partitioning and reconstruction problem has two distinct advantages compared with the harmonic-sine series expansion. The first is that the internal and harmonic winds can be more accurately determined at the boundary. The second is that the partitioning of the wind field into streamfunction and velocity potential can be obtained more efficiently and accurately through an iterative method.

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# An Equivalent Isobaric Geopotential Height and Its Application to Synoptic Analysis and a Generalized ω Equation in σ Coordinates

Qiu-shi Chen
and
David H. Bromwich

## Abstract

In σ coordinates, a variable ϕ e (x, y, σ, t) whose horizontal gradient − ϕ e is equal to the irrotational part of the horizontal pressure gradient force is referred to as an equivalent isobaric geopotential height. Its inner part can be derived from the solution of a Poisson equation with zero Dirichlet boundary value. Because − ϕ(x, y, p, t) is also the irrotational part of the horizontal pressure gradient force in p coordinates, the equivalent geopotential ϕ e in σ coordinates can be used in the same way as the geopotential ϕ(x, y, p, t) used in p coordinates. In the sea level pressure (SLP) analysis over Greenland, small but strong high pressure systems often occur due to extrapolation. These artificial systems can be removed if the equivalent geopotential ϕ e is used in synoptic analysis on a constant σ surface, for example, at σ = 0.995 level. The geostrophic relation between the equivalent geopotential and streamfunction at σ = 0.995 is approximately satisfied.

Because weather systems over the Tibetan Plateau are very difficult to track using routine SLP, 850-hPa, and 700-hPa analyses, equivalent isobaric geopotential analysis in σ coordinates is especially useful over this area. An example of equivalent isobaric geopotential analysis at σ = 0.995 shows that a secondary high separated from a major anticyclone over the Tibetan Plateau when cold air affected the northeastern part of the plateau, but this secondary high is hardly resolved by the SLP analysis. The early stage of a low (or vortex), called a southwest vortex due to its origin in southwest China, over the eastern flank of the Tibetan Plateau is more clearly identified by equivalent isobaric geopotential analysis at σ = 0.825 and 0.735 than by routine isobaric analysis at the 850- and 700-hPa levels. Anomalous high and low systems in the SLP analysis over the Tibetan Plateau due to extrapolation are all removed by equivalent isobaric geopotential analysis at σ = 0.995.

Use of equivalent geopotential ϕ e in the vorticity and divergence equations is presented, and the equivalent geopotential equation is derived. These equations can be used in numerical models, initializations, and other dynamical studies. As an example, it is shown how these equations are used to derive a velocity potential form of the generalized ω equation in σ coordinates. As a check, retrieval of precipitation over Greenland using this ω equation shows that the computed precipitation distributions for 1987 and 1988 are in good agreement with the observed annual accumulation.

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# A Harmonic-Fourier Spectral Limited-Area Model with an External Wind Lateral Boundary Condition

Qiu-shi Chen
,
Le-sheng Bai
, and
David H. Bromwich

## Abstract

In comparison to the Tatsumi’s spectral method, the harmonic-Fourier spectral method has two major advantages. 1) The semi-implicit scheme is quite efficient because the solutions of the Poisson and Helmholtz equations are readily derived. 2) The lateral boundary value problem of a limited-area model is easily solved. These advantages are the same as those of the spherical harmonics used in global models if the singularity at the pole points for a globe is considered to be the counterpart of the lateral boundary condition for a limited region.

If a limited-area model is nested in a global model, the prediction of the limited-area model at each time step is the sum of the inner part and the harmonic part predictions. The inner part prediction is solved by the double sine series from the inner part equations for the limited-area model. The harmonic part prediction is derived from the prediction of the global model. An external wind lateral boundary method is proposed based on the basic property of the wind separation in a limited region. The boundary values of a limited-area model in this method are not given at the closed boundary line, but always given by harmonic functions defined throughout the limited domain. The harmonic functions added to the inner parts at each time step represent the effects of the lateral boundary values on the prediction of the limited-area model, and they do not cause any discontinuity near the boundary.

Tests show that predicted motion systems move smoothly in and out through the boundary, where the predicted variables are very smooth without any other boundary treatment. In addition, the boundary method can also be used in the most complicated mountainous region where the boundary intersects high mountains. The tests also show that the adiabatic dynamical part of the limited-area model very accurately predicts the rapid development of a cyclone caused by dry baroclinic instability along the east coast of North America and a lee cyclogenesis case in East Asia. The predicted changes of intensity and location of both cyclones are close to those given by the observations.

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# Modeled Antarctic Precipitation. Part I: Spatial and Temporal Variability

David H. Bromwich
,
Zhichang Guo
,
Lesheng Bai
, and
Qiu-shi Chen

## Abstract

Surface snow accumulation is the primary mass input to the Antarctic ice sheets. As the dominant term among various components of surface snow accumulation (precipitation, sublimation/deposition, and snow drift), precipitation is of particular importance in helping to assess the mass balance of the Antarctic ice sheets and their contribution to global sea level change.

The Polar MM5, a mesoscale atmospheric model based on the fifth-generation Pennsylvania State University–NCAR Mesoscale Model, has been run for the period of July 1996 through June 1999 to evaluate the spatial and temporal variability of Antarctic precipitation. Drift snow effects on the redistribution of surface snow over Antarctica are also assessed with surface wind fields from Polar MM5 in this study. It is found that areas with large drift snow transport convergence and divergence are located around escarpment areas where there is considerable katabatic wind acceleration. It is also found that the drift snow transport generally diverges over most areas of East and West Antarctica with relatively small values.

The use of the dynamic retrieval method (DRM) to calculate precipitation has been developed and verified for the Greenland ice sheet. The DRM is also applied to retrieve the precipitation over Antarctica from 1979 to 1999 in this study. Most major features in the spatial distribution of Antarctic accumulation are well captured by the DRM results. In comparison with predicted precipitation amounts from atmospheric analyses and reanalyses, DRM calculations capture more mesoscale features of the precipitation distribution over Antarctica. A significant upward trend of +1.3 to +1.7 mm yr−2 for 1979–99 is found from DRM and forecast precipitation amounts for Antarctica that is consistent with results reported by other investigators and indicates that an additional 0.05 mm yr−1 is being extracted from the global ocean and locked up in the Antarctic ice sheets. While there is good agreement in this trend among all of the datasets, the interannual variability about the trend on the continental scale is not well captured. However, on the subcontinental scale, the interannual variability about the trend is well resolved for sectors in West Antarctica and the South Atlantic. It is also noted that the precipitation trend is weakly downward over much of the continent.

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# Precipitation over Greenland Retrieved by a Dynamic Method and Its Relation to Cyclonic Activity

Qiu-shi Chen
,
David H. Bromwich
, and
Lesheng Bai

## Abstract

In order to calculate the vertical motion over some high mountain regions, such as Greenland, an ω-equation without the quasigeostrophic approximation in σ-coordinates has been developed. A dynamic method for retrieving precipitation over Greenland is based on this ω-equation. The retrieved annual mean precipitation distribution for 1987 and 1988 is in very good agreement with the observed annual accumulation pattern over the Greenland Ice Sheet.

The major weather system producing precipitation over Greenland is the frontal cyclone. Based on the precipitation characteristics, Greenland can be divided into five subregions. Precipitation over the north coastal and central interior regions primarily occurs in summer. For the three other subregions, if the composite monthly mean sea level pressure charts for high and low monthly precipitation amounts are constructed, a clear relationship between precipitation and cyclonic activity emerges. If a mean cyclone exists in the Labrador Sea, heavy precipitation will fall over Greenland during that month. By contrast, if a mean cyclone exists near Iceland, precipitation over Greenland will be reduced. This is an important relationship between Greenland precipitation and cyclonic activity.

The cyclonic tracks near Greenland are established. A synoptic example is used to show the relation between precipitation and a cyclone moving up the west side of Greenland (track B) combined with movement across the southern tip of the island (track C). In this example, lee cyclogenesis is caused by the southern part of the Greenland Ice Sheet. The lee cyclone develops on the east coast along track C. During lee cyclogenesis, heavy precipitation falls over the southern region. The “parent” cyclone moves along track B, and precipitation falls along the west coast of Greenland.

A possible feedback between cyclonic activity and the mass balance of the Greenland Ice Sheet is proposed. On the one hand, cyclonic activity has a significant influence on snow accumulation over the ice sheet. The development of Icelandic cyclones is not favorable for precipitation over Greenland. On the other hand, the Greenland Ice Sheet has an important dynamic effect in producing lee cyclogenesis and affecting the frequency of Icelandic cyclones. This possible feedback may be important for understanding how the mass balance of the Greenland Ice Sheet and the Icelandic low are maintained in the present climate state.

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# Applications of Bivariate Fourier Series for Solving the Poisson Equation in Limited-Area Modeling of the Atmosphere: Higher Accuracy with a Boundary Buffer Strip Discarded and an Improved Order-Raising Procedure

John P. Boyd
,
Difei Deng
,
Qiu-Shi Chen
, and
Shouting Gao

## Abstract

Bivariate Fourier series have many benefits in limited-area modeling (LAM), weather forecasting, and meteorological data analysis. However, atmospheric data are not spatially periodic on the LAM domain (“window”), which can be normalized to the unit square (x, y) ∈ [0, 1] ⊗ [0, 1] by rescaling the coordinates. Most Fourier LAM meteorology has employed rather low-order methods that have been quite successful in spite of Gibbs phenomenon at the boundaries of the artificial periodicity window. In this article, the authors explain why. Because data near the boundary between the high-resolution LAM window and the low-resolution global model are necessarily suspect, corrupted by the discontinuity in resolution, meteorologists routinely ignore LAM results in a buffer strip of nondimensional width D, and analyze only the Fourier sums in the smaller domain (x, y) ∈ [D, 1 − D] ⊗ [D, 1 − D]. It is shown that the error in a one-dimensional Fourier series with N terms or in a two-dimensional series with N 2 terms, is smaller by a factor of N on a boundary-buffer-discarded domain than on the full unit square. A variety of procedures for raising the order of Fourier series convergence are described, and it is explained how the deletion of the boundary strip greatly simplifies and improves these enhancements. The prime exemplar is solving the Poisson equation with homogeneous boundary conditions by sine series, but the authors also discuss the Laplace equation with inhomogeneous boundary conditions.

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# Spring Land Temperature in Tibetan Plateau and Global-Scale Summer Precipitation: Initialization and Improved Prediction

Yongkang Xue
,
Ismaila Diallo
,
Aaron A. Boone
,
Tandong Yao
,
Yang Zhang
,
Xubin Zeng
,
J. David Neelin
,
William K. M. Lau
,
Yan Pan
,
Ye Liu
,
Xiaoduo Pan
,
Qi Tang
,
Peter J. van Oevelen
,
Tomonori Sato
,
Myung-Seo Koo
,
Stefano Materia
,
Chunxiang Shi
,
Jing Yang
,
Constantin Ardilouze
,
Zhaohui Lin
,
Xin Qi
,
Tetsu Nakamura
,
Subodh K. Saha
,
Retish Senan
,
Yuhei Takaya
,
Hailan Wang
,
Hongliang Zhang
,
Mei Zhao
,
,
Qiuyu Chen
,
Jinming Feng
,
Michael A. Brunke
,
Tianyi Fan
,
Songyou Hong
,
Paulo Nobre
,
Daniele Peano
,
Yi Qin
,
Frederic Vitart
,
Shaocheng Xie
,
Yanling Zhan
,
Daniel Klocke
,
Ruby Leung
,
Xin Li
,
Michael Ek
,
Weidong Guo
,
Gianpaolo Balsamo
,
Qing Bao
,
Sin Chan Chou
,
Patricia de Rosnay
,
Yanluan Lin
,
Yuejian Zhu
,
Yun Qian
,
Ping Zhao
,
Jianping Tang
,
Xin-Zhong Liang
,
Jinkyu Hong
,
Duoying Ji
,
Zhenming Ji
,
Yuan Qiu
,
Shiori Sugimoto
,
Weicai Wang
,
Kun Yang
, and
Miao Yu

## Abstract

Subseasonal-to-seasonal (S2S) precipitation prediction in boreal spring and summer months, which contains a significant number of high-signal events, is scientifically challenging and prediction skill has remained poor for years. Tibetan Plateau (TP) spring observed surface ­temperatures show a lag correlation with summer precipitation in several remote regions, but current global land–atmosphere coupled models are unable to represent this behavior due to significant errors in producing observed TP surface temperatures. To address these issues, the Global Energy and Water Exchanges (GEWEX) program launched the “Impact of Initialized Land Temperature and Snowpack on Subseasonal-to-Seasonal Prediction” (LS4P) initiative as a community effort to test the impact of land temperature in high-mountain regions on S2S prediction by climate models: more than 40 institutions worldwide are participating in this project. After using an innovative new land state initialization approach based on observed surface 2-m temperature over the TP in the LS4P experiment, results from a multimodel ensemble provide evidence for a causal relationship in the observed association between the Plateau spring land temperature and summer precipitation over several regions across the world through teleconnections. The influence is underscored by an out-of-phase oscillation between the TP and Rocky Mountain surface temperatures. This study reveals for the first time that high-mountain land temperature could be a substantial source of S2S precipitation predictability, and its effect is probably as large as ocean surface temperature over global “hotspot” regions identified here; the ensemble means in some “hotspots” produce more than 40% of the observed anomalies. This LS4P approach should stimulate more follow-on explorations.

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# Introduction

Tim Boyer
,
Ellen Bartow-Gillies
,
A. Abida
,
,
,
,
W. Agyakwah
,
Brandon Ahmasuk
,
Laura S. Aldeco
,
Mihai Alexe
,
Eric J. Alfaro
,
Richard P. Allan
,
,
Lincoln. M. Alves
,
,
John Anderson
,
,
Orlane Anneville
,
Yasuyuki Aono
,
Anthony Arguez
,
Carlo Arosio
,
C. Atkinson
,
John A. Augustine
,
Grinia Avalos
,
Cesar Azorin-Molina
,
Stacia A. Backensto
,
,
Julian Baez
,
Rebecca Baiman
,
Thomas J. Ballinger
,
Alison F. Banwell
,
M. Yu Bardin
,
Jonathan Barichivich
,
John E. Barnes
,
Sandra Barreira
,
,
Hylke E. Beck
,
Emily J. Becker
,
E. Bekele
,
Guillem Martín Bellido
,
Nicolas Bellouin
,
Angela Benedetti
,
,
Christine Berne
,
Logan. T. Berner
,
Germar H. Bernhard
,
Uma S. Bhatt
,
A. E. Bhuiyan
,
Siiri Bigalke
,
Tiago Biló
,
Peter Bissolli
,
W. Bjerke Jarle
,
Kevin Blagrave
,
Eric S. Blake
,
Stephen Blenkinsop
,
Jessica Blunden
,
Oliver Bochníček
,
Olivier Bock
,
Xavier Bodin
,
Michael Bosilovich
,
Olivier Boucher
,
Deniz Bozkurt
,
Brian Brettschneider
,
Francis G. Bringas
,
Francis Bringas
,
Dennis Buechler
,
Stefan A. Buehler
,
Brandon Bukunt
,
Blanca Calderón
,
Suzana J. Camargo
,
Jayaka Campbell
,
Diego Campos
,
Laura Carrea
,
Brendan R. Carter
,
Ivona Cetinić
,
Don P. Chambers
,
Duo Chan
,
Elise Chandler
,
Kai-Lan Chang
,
Hua Chen
,
Lin Chen
,
Lijing Cheng
,
Vincent Y. S. Cheng
,
Leah Chomiak
,
Hanne H. Christiansen
,
John R. Christy
,
Eui-Seok Chung
,
Laura M. Ciasto
,
Leonardo Clarke
,
Kyle R. Clem
,
Scott Clingan
,
Caio A.S. Coelho
,
Judah L. Cohen
,
Melanie Coldewey-Egbers
,
Steve Colwell
,
Owen R. Cooper
,
Richard C. Cornes
,
Kris Correa
,
Felipe Costa
,
Curt Covey
,
Lawrence Coy
,
Jean-François Créatux
,
Lenka Crhova
,
Theresa Crimmins
,
Meghan F. Cronin
,
Thomas Cropper
,
Molly Crotwell
,
Joshua Culpepper
,
Ana P. Cunha
,
Diego Cusicanqui
,
Rajashree T. Datta
,
Sean M. Davis
,
Veerle De Bock
,
Richard A. M. de Jeu
,
Jos De Laat
,
Bertrand Decharme
,
Doug Degenstein
,
Reynald Delaloye
,
Mesut Demircan
,
Chris Derksen
,
Ricardo Deus
,
K. R. Dhurmea
,
Howard J. Diamond
,
S. Dirkse
,
Dmitry Divine
,
Martin T. Dokulil
,
Markus G. Donat
,
Shenfu Dong
,
Wouter A. Dorigo
,
Caroline Drost Jensen
,
Matthew L. Druckenmiller
,
Paula Drumond
,
Marcel du Plessis
,
Hilary A. Dugan
,
Dashkhuu Dulamsuren
,
Devon Dunmire
,
Robert J. H. Dunn
,
Imke Durre
,
Geoff Dutton
,
Gregory Duveiller
,
Mithat Ekici
,
Alesksandra Elias Chereque
,
M. ElKharrim
,
Howard E. Epstein
,
Jhan-Carlo Espinoza
,
Thomas W. Estilow
,
Nicole Estrella
,
Nicolas Fauchereau
,
Robert S. Fausto
,
Richard A. Feely
,
Chris Fenimore
,
David Fereday
,
Xavier Fettweis
,
vitali E. Fioletov
,
Johannes Flemming
,
Chris Fogarty
,
Ryan L. Fogt
,
Bruce C. Forbes
,
Michael J. Foster
,
Bryan A. Franz
,
Natalie M. Freeman
,
Helen A. Fricker
,
Stacey M. Frith
,
Lucien Froidevaux
,
(JJ)
,
Steven Fuhrman
,
Martin Füllekrug
,
Catherine Ganter
,
Meng Gao
,
Alex S. Gardner
,
Judith Garforth
,
Jay Garg
,
Sebastian Gerland
,
,
Sarah T. Gille
,
John Gilson
,
Karin Gleason
,
,
Scott J. Goetz
,
Stanley B. Goldenberg
,
Gustavo Goni
,
Steven Goodman
,
Atsushi Goto
,
Jens-Uwe Grooß
,
Alexander Gruber
,
Guojun Gu
,
Charles “Chip” P. Guard
,
S. Hagos
,
Sebastian Hahn
,
Leopold Haimberger
,
,
Benjamin D. Hamlington
,
Edward Hanna
,
Inger Hanssen-Bauer
,
Daniel S. Harnos
,
Ian Harris
,
Qiong He
,
Richard R. Heim Jr.
,
Sverker Hellström
,
Deborah L. Hemming
,
Stefan Hendricks
,
J. Hicks
,
Hugo G. Hidalgo
,
Martin Hirschi
,
(Ben)
,
W. Hobbs
,
Robert M. Holmes
,
Robert Holzworth
,
Filip Hrbáček
,
Guojie Hu
,
Zeng-Zhen Hu
,
Boyin Huang
,
Hongjie Huang
,
Dale F. Hurst
,
Iolanda Ialongo
,
Antje Inness
,
Ketil Isaksen
,
Masayoshi Ishii
,
,
Svetlana Jevrejeva
,
Viju O. John
,
W. Johns
,
Bjørn Johnsen
,
Bryan Johnson
,
Gregory C. Johnson
,
Philip D. Jones
,
Timothy Jones
,
Simon A. Josey
,
G. Jumaux
,
Robert Junod
,
Andreas Kääb
,
K. Kabidi
,
Johannes W. Kaiser
,
Robb S.A. Kaler
,
Lars Kaleschke
,
Viktor Kaufmann
,
Amin Fazl Kazemi
,
Linda M. Keller
,
Andreas Kellerer-Pirklbauer
,
Mike Kendon
,
John Kennedy
,
Elizabeth C. Kent
,
Kenneth Kerr
,
Valentina Khan
,
Mai Van Khiem
,
Richard Kidd
,
Mi Ju Kim
,
Seong-Joong Kim
,
Zak Kipling
,
Philip J. Klotzbach
,
John A. Knaff
,
Akash Koppa
,
Natalia N. Korshunova
,
Benjamin M. Kraemer
,
Natalya A. Kramarova
,
A. C. Kruger
,
Andries Kruger
,
Arun Kumar
,
Michelle L’Heureux
,
Sofia La Fuente
,
Alo Laas
,
Zachary M. Labe
,
,
Mónika Lakatos
,
Kaisa Lakkala
,
Hoang Phuc Lam
,
Xin Lan
,
Peter Landschützer
,
Chris W. Landsea
,
Timothy Lang
,
Matthias Lankhorst
,
Kathleen O. Lantz
,
Mark J. Lara
,
,
David A. Lavers
,
Matthew A. Lazzara
,
Thierry Leblanc
,
Tsz-Cheung Lee
,
Eric M. Leibensperger
,
Chris Lennard
,
Eric Leuliette
,
Kinson H. Y. Leung
,
Jan L. Lieser
,
Tanja Likso
,
I-I. Lin
,
Jackie Lindsey
,
Yakun Liu
,
Ricardo Locarnini
,
Norman G. Loeb
,
Bryant D. Loomis
,
Andrew M. Lorrey
,
Diego Loyola
,
Rui Lu
,
Rick Lumpkin
,
Jing-Jia Luo
,
Kari Luojus
,
John M. Lyman
,
Stephen C. Maberly
,
Matthew J. Macander
,
Michael MacFerrin
,
Graeme A. MacGilchrist
,
Michelle L. MacLennan
,
,
Andrew D. Magee
,
Florence Magnin
,
Jostein Mamen
,
Ken D. Mankoff
,
Gloria L. Manney
,
Izolda Marcinonienė
,
Jose A. Marengo
,
,
Ana E. Martínez
,
Robert A. Massom
,
Shin-Ichiro Matsuzaki
,
Linda May
,
Michael Mayer
,
Matthew R. Mazloff
,
Stephanie A. McAfee
,
C. McBride
,
Matthew F. McCabe
,
James W. McClelland
,
,
Tim R. Mcvicar
,
Carl A. Mears
,
Walter N. Meier
,
A. Mekonnen
,
Annette Menzel
,
Christopher J. Merchant
,
Mark A. Merrifield
,
Michael F. Meyer
,
Tristan Meyers
,
David E. Mikolajczyk
,
John B. Miller
,
Diego G. Miralles
,
Noelia Misevicius
,
Alexey Mishonov
,
Gary T. Mitchum
,
Ben I. Moat
,
Leander Moesinger
,
Aurel Moise
,
Jorge Molina-Carpio
,
Ghislaine Monet
,
Stephan A. Montzka
,
Twila A. Moon
,
G. W. K. Moore
,
Natali Mora
,
Johnny Morán
,
Claire Morehen
,
Colin Morice
,
A. E. Mostafa
,
Thomas L. Mote
,
Ivan Mrekaj
,
Lawrence Mudryk
,
Jens Mühle
,
Rolf Müller
,
David Nance
,
Eric R. Nash
,
R. Steven Nerem
,
Paul A. Newman
,
Julien P. Nicolas
,
Juan J. Nieto
,
Jeannette Noetzli
,
Ben Noll
,
Taylor Norton
,
Kelsey E. Nyland
,
John O’Keefe
,
Naomi Ochwat
,
Yoshinori Oikawa
,
Yuka Okunaka
,
Timothy J. Osborn
,
James E. Overland
,
Taejin Park
,
Mark Parrington
,
Julia K. Parrish
,
Richard J. Pasch
,
Reynaldo Pascual Ramírez
,
Cécile Pellet
,
Mauri S. Pelto
,
,
Donald K. Perovich
,
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## Abstract

—J. BLUNDEN, T. BOYER, AND E. BARTOW-GILLIES

Earth’s global climate system is vast, complex, and intricately interrelated. Many areas are influenced by global-scale phenomena, including the “triple dip” La Niña conditions that prevailed in the eastern Pacific Ocean nearly continuously from mid-2020 through all of 2022; by regional phenomena such as the positive winter and summer North Atlantic Oscillation that impacted weather in parts the Northern Hemisphere and the negative Indian Ocean dipole that impacted weather in parts of the Southern Hemisphere; and by more localized systems such as high-pressure heat domes that caused extreme heat in different areas of the world. Underlying all these natural short-term variabilities are long-term climate trends due to continuous increases since the beginning of the Industrial Revolution in the atmospheric concentrations of Earth’s major greenhouse gases.

In 2022, the annual global average carbon dioxide concentration in the atmosphere rose to 417.1±0.1 ppm, which is 50% greater than the pre-industrial level. Global mean tropospheric methane abundance was 165% higher than its pre-industrial level, and nitrous oxide was 24% higher. All three gases set new record-high atmospheric concentration levels in 2022.

Sea-surface temperature patterns in the tropical Pacific characteristic of La Niña and attendant atmospheric patterns tend to mitigate atmospheric heat gain at the global scale, but the annual global surface temperature across land and oceans was still among the six highest in records dating as far back as the mid-1800s. It was the warmest La Niña year on record. Many areas observed record or near-record heat. Europe as a whole observed its second-warmest year on record, with sixteen individual countries observing record warmth at the national scale. Records were shattered across the continent during the summer months as heatwaves plagued the region. On 18 July, 104 stations in France broke their all-time records. One day later, England recorded a temperature of 40°C for the first time ever. China experienced its second-warmest year and warmest summer on record. In the Southern Hemisphere, the average temperature across New Zealand reached a record high for the second year in a row. While Australia’s annual temperature was slightly below the 1991–2020 average, Onslow Airport in Western Australia reached 50.7°C on 13 January, equaling Australia's highest temperature on record.

While fewer in number and locations than record-high temperatures, record cold was also observed during the year. Southern Africa had its coldest August on record, with minimum temperatures as much as 5°C below normal over Angola, western Zambia, and northern Namibia. Cold outbreaks in the first half of December led to many record-low daily minimum temperature records in eastern Australia.

The effects of rising temperatures and extreme heat were apparent across the Northern Hemisphere, where snow-cover extent by June 2022 was the third smallest in the 56-year record, and the seasonal duration of lake ice cover was the fourth shortest since 1980. More frequent and intense heatwaves contributed to the second-greatest average mass balance loss for Alpine glaciers around the world since the start of the record in 1970. Glaciers in the Swiss Alps lost a record 6% of their volume. In South America, the combination of drought and heat left many central Andean glaciers snow free by mid-summer in early 2022; glacial ice has a much lower albedo than snow, leading to accelerated heating of the glacier. Across the global cryosphere, permafrost temperatures continued to reach record highs at many high-latitude and mountain locations.

In the high northern latitudes, the annual surface-air temperature across the Arctic was the fifth highest in the 123-year record. The seasonal Arctic minimum sea-ice extent, typically reached in September, was the 11th-smallest in the 43-year record; however, the amount of multiyear ice—ice that survives at least one summer melt season—remaining in the Arctic continued to decline. Since 2012, the Arctic has been nearly devoid of ice more than four years old.

In Antarctica, an unusually large amount of snow and ice fell over the continent in 2022 due to several landfalling atmospheric rivers, which contributed to the highest annual surface mass balance, 15% to 16% above the 1991–2020 normal, since the start of two reanalyses records dating to 1980. It was the second-warmest year on record for all five of the long-term staffed weather stations on the Antarctic Peninsula. In East Antarctica, a heatwave event led to a new all-time record-high temperature of −9.4°C—44°C above the March average—on 18 March at Dome C. This was followed by the collapse of the critically unstable Conger Ice Shelf. More than 100 daily low sea-ice extent and sea-ice area records were set in 2022, including two new all-time annual record lows in net sea-ice extent and area in February.

Across the world’s oceans, global mean sea level was record high for the 11th consecutive year, reaching 101.2 mm above the 1993 average when satellite altimetry measurements began, an increase of 3.3±0.7 over 2021. Globally-averaged ocean heat content was also record high in 2022, while the global sea-surface temperature was the sixth highest on record, equal with 2018. Approximately 58% of the ocean surface experienced at least one marine heatwave in 2022. In the Bay of Plenty, New Zealand’s longest continuous marine heatwave was recorded.

A total of 85 named tropical storms were observed during the Northern and Southern Hemisphere storm seasons, close to the 1991–2020 average of 87. There were three Category 5 tropical cyclones across the globe—two in the western North Pacific and one in the North Atlantic. This was the fewest Category 5 storms globally since 2017. Globally, the accumulated cyclone energy was the lowest since reliable records began in 1981. Regardless, some storms caused massive damage. In the North Atlantic, Hurricane Fiona became the most intense and most destructive tropical or post-tropical cyclone in Atlantic Canada’s history, while major Hurricane Ian killed more than 100 people and became the third costliest disaster in the United States, causing damage estimated at \$113 billion U.S. dollars. In the South Indian Ocean, Tropical Cyclone Batsirai dropped 2044 mm of rain at Commerson Crater in Réunion. The storm also impacted Madagascar, where 121 fatalities were reported.

As is typical, some areas around the world were notably dry in 2022 and some were notably wet. In August, record high areas of land across the globe (6.2%) were experiencing extreme drought. Overall, 29% of land experienced moderate or worse categories of drought during the year. The largest drought footprint in the contiguous United States since 2012 (63%) was observed in late October. The record-breaking megadrought of central Chile continued in its 13th consecutive year, and 80-year record-low river levels in northern Argentina and Paraguay disrupted fluvial transport. In China, the Yangtze River reached record-low values. Much of equatorial eastern Africa had five consecutive below-normal rainy seasons by the end of 2022, with some areas receiving record-low precipitation totals for the year. This ongoing 2.5-year drought is the most extensive and persistent drought event in decades, and led to crop failure, millions of livestock deaths, water scarcity, and inflated prices for staple food items.

In South Asia, Pakistan received around three times its normal volume of monsoon precipitation in August, with some regions receiving up to eight times their expected monthly totals. Resulting floods affected over 30 million people, caused over 1700 fatalities, led to major crop and property losses, and was recorded as one of the world’s costliest natural disasters of all time. Near Rio de Janeiro, Brazil, Petrópolis received 530 mm in 24 hours on 15 February, about 2.5 times the monthly February average, leading to the worst disaster in the city since 1931 with over 230 fatalities.

On 14–15 January, the Hunga Tonga-Hunga Ha'apai submarine volcano in the South Pacific erupted multiple times. The injection of water into the atmosphere was unprecedented in both magnitude—far exceeding any previous values in the 17-year satellite record—and altitude as it penetrated into the mesosphere. The amount of water injected into the stratosphere is estimated to be 146±5 Terragrams, or ∼10% of the total amount in the stratosphere. It may take several years for the water plume to dissipate, and it is currently unknown whether this eruption will have any long-term climate effect.

Open access