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4. Seasonal Prediction and Predictability of Regional Antarctic Sea Ice

Author

Bushuk, Mitchell, Winton, Michael, Haumann, F. Alexander, Delworth, Thomas, Lu, Feiyu, Zhang, Yongfei, Jia, Liwei, Zhang, Liping, Cooke, William, Harrison, Matthew, Hurlin, Bill, Johnson, Nathaniel C., Kapnick, Sarah B., McHugh, Colleen, Murakami, Hiroyuki, Rosati, Anthony, Tseng, Kai-Chih, Wittenberg, Andrew T., Yang, Xiaosong, and Zeng, Fanrong

Published
2021

5. EXPLAINING EXTREME EVENTS OF 2016 : From A Climate Perspective

Author

Herring, Stephanie C., Christidi, Nikolaos, Hoell, Andrew, Kossin, James P., Schreck, Carl J., Stott, Peter A., Webb, Robert S., Werner, Francisco E., Knutson, Thomas R., Kam, Jonghun, Zeng, Fanrong, Wittenberg, Andrew T., Brainard, Russell E., Oliver, Thomas, McPhaden, Michael J., Cohen, Anne, Venegas, Robert o, Heenan, Adel, Vargas-Ángel, Bernardo, Rotjan, Randi, Mangubhai, Sangeeta, Flint, Elizabeth, Hunter, Susan A., Oliver, Eric C. J., Perkins-Kirkpatrick, Sarah E., Holbrook, Neil J., Bindoff, Nathaniel L., Tett, Simon F. B., Falk, Alexander, Rogers, Megan, Spuler, Fiona, Turner, Calum, Wainwright, Joshua, Dimdore-Miles, Oscar, Knight, Sam, Freychet, Nicolas, Mineter, Michael J., Lehmann, Caroline E. R., Martins, Eduardo S. P. R., Coelho, Caio A. S., Haarsma, Rein, Otto, Friederike E. L., King, Andrew D., van Oldenborgh, Geert Jan, Kew, Sarah, Philip, Sjoukje, Vasconcelos, Francisco C., Cullen, Heidi, Jézéquel, Aglaé, Yiou, Pascal, Radanovics, Sabine, Vautard, Robert, Sippel, Sebastian, El-Madany, Tarek S., Migliavacca, Mirco, Mahecha, Miguel D., Carrara, Arnaud, Flach, Milan, Kaminski, Thomas, Otto, Friederike E. L., Thonicke, Kirsten, Vossbeck, Michael, Reichstein, Markus, Yuan, Xing, Wang, Linying, Wood, Eric F., Funk, Chris, Davenport, Frank, Harrison, Laura, Magadzire, Tamuka, Galu, Gideon, Artan, Guleid A., Shukla, Shraddhanand, Korecha, Diriba, Indeje, Matayo, Pomposi, Catherine, Macharia, Denis, Husak, Gregory, Nsadisa, Faka Dieudonne, Imada, Yukiko, Shiogama, Hideo, Takahashi, Chiharu, Watanabe, Masahiro, Mori, Masato, Kamae, Youichi, Maeda, Shuhei, Sun, Qiaohong, Miao, Chiyuan, Zhou, Chunlüe, Wang, Kaicun, Qi, Dan, Yuan, Xing, Wang, Shanshan, Hu, Zeng-Zhen, Qian, Cheng, Wang, Jun, Dong, Siyan, Yin, Hong, Burke, Claire, Ciavarella, Andrew, Dong, Buwen, Freychet, Nicolas, Lott, Fraser C., Tett, Simon F. B., Sun, Ying, Hu, Ting, Zhang, Xuebin, Wan, Hui, Stott, Peter, Lu, Chunhui, Christidis, Nikolaos, Manomaiphiboon, Kasemsan, Ciavarella, Andrew, Stott, Peter A., Hope, Pandora, Lim, Eun-Pa, Hendon, Harry, Wang, Guomin, Lewis, Sophie C., Mallela, Jennie, Grose, Michael R., Black, Mitchell, Risbey, James S., Uhe, Peter, Hope, Pandora K., Haustein, Karsten, Mitchell, Dann, Stott, Peter A., Christidis, Nikos, Herring, Stephanie C., Hoell, Andrew, Kossin, James P., and Schreck, Carl J.

Published
2018

12. Estimating Uncertainty in Simulated ENSO Statistics.

Author

Planton, Yann Y., Lee, Jiwoo, Wittenberg, Andrew T., Gleckler, Peter J., Guilyardi, Éric, McGregor, Shayne, and McPhaden, Michael J.

Subjects
GREENHOUSE gases, CLIMATE change models, OCEAN temperature, ATMOSPHERIC models, SQUARE root
Abstract

Large ensembles of model simulations are frequently used to reduce the impact of internal variability when evaluating climate models and assessing climate change induced trends. However, the optimal number of ensemble members required to distinguish model biases and climate change signals from internal variability varies across models and metrics. Here we analyze the mean, variance and skewness of precipitation and sea surface temperature in the eastern equatorial Pacific region often used to describe the El Niño–Southern Oscillation (ENSO), obtained from large ensembles of Coupled model intercomparison project phase 6 climate simulations. Leveraging established statistical theory, we develop and assess equations to estimate, a priori, the ensemble size or simulation length required to limit sampling‐based uncertainties in ENSO statistics to within a desired tolerance. Our results confirm that the uncertainty of these statistics decreases with the square root of the time series length and/or ensemble size. Moreover, we demonstrate that uncertainties of these statistics are generally comparable when computed using either pre‐industrial control or historical runs. This suggests that pre‐industrial runs can sometimes be used to estimate the expected uncertainty of statistics computed from an existing historical member or ensemble, and the number of simulation years (run duration and/or ensemble size) required to adequately characterize the statistic. This advance allows us to use existing simulations (e.g., control runs that are performed during model development) to design ensembles that can sufficiently limit diagnostic uncertainties arising from simulated internal variability. These results may well be applicable to variables and regions beyond ENSO. Plain Language Summary: Earth's climate naturally fluctuates on intraseasonal to interdecadal timescales, confounding the evaluation of climate models and the detection of trends linked to climate change. To tackle this challenge, scientists produce ensembles of simulations with identical external forcings (e.g., volcanic eruptions, greenhouse gas emissions) but plausibly different initial conditions. In this study, we analyze how these ensembles can be used to reduce the uncertainty of the simulated climate, to help guide the design of future ensembles and optimize the use of available computing resources. Key Points: Large ensembles of climate simulations are analyzed to characterize the sampling uncertainty of El Niño–Southern Oscillation statisticsAs expected, uncertainty of these statistics decreases with the square root of the number of simulated years provided by the ensembleA simple equation developed to predict the ensemble size required to limit this sampling uncertainty to within a given tolerance [ABSTRACT FROM AUTHOR]

Published
2024
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18. Seasonal predictability of baroclinic wave activity

Author

Zhang, Gan, Murakami, Hiroyuki, Cooke, William F., Wang, Zhuo, Jia, Liwei, Lu, Feiyu, Yang, Xiaosong, Delworth, Thomas L., Wittenberg, Andrew T., Harrison, Matthew J., Bushuk, Mitchell, McHugh, Colleen, Johnson, Nathaniel C., Kapnick, Sarah B., Tseng, Kai-Chih, and Zhang, Liping

Published
2021
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19. Tropical cyclone sensitivities to CO2 doubling: roles of atmospheric resolution, synoptic variability and background climate changes

Author

Vecchi, Gabriel A., Delworth, Thomas L., Murakami, Hiroyuki, Underwood, Seth D., Wittenberg, Andrew T., Zeng, Fanrong, Zhang, Wei, Baldwin, Jane W., Bhatia, Kieran T., Cooke, William, He, Jie, Kapnick, Sarah B., Knutson, Thomas R., Villarini, Gabriele, van der Wiel, Karin, Anderson, Whit, Balaji, V., Chen, Jan–Huey, Dixon, Keith W., Gudgel, Rich, Harris, Lucas M., Jia, Liwei, Johnson, Nathaniel C., Lin, Shian-Jiann, Liu, Maofeng, Ng, Ching Ho Justin, Rosati, Anthony, Smith, James A., and Yang, Xiaosong

Published
2019
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22. OBSERVING AND PREDICTING THE 2015/16 EL NIÑO

Author

L’Heureux, Michelle L., Takahashi, Ken, Watkins, Andrew B., Barnston, Anthony G., Becker, Emily J., Di Liberto, Tom E., Gamble, Felicity, Gottschalck, Jon, Halpert, Michael S., Huang, Boyin, Mosquera-Vásquez, Kobi, and Wittenberg, Andrew T.

Published
2017

23. SUPPLEMENT : OBSERVING AND PREDICTING THE 2015/16 EL NIÑO

Author

L’Heureux, Michelle L., Takahashi, Ken, Watkins, Andrew B., Barnston, Anthony G., Becker, Emily J., Di Liberto, Tom E., Gamble, Felicity, Gottschalck, Jon, Halpert, Michael S., Huang, Boyin, Mosquera-Vásquez, Kobi, and Wittenberg, Andrew T.

Published
2017

30. 7. CMIP5 MODEL-BASED ASSESSMENT OF ANTHROPOGENIC INFLUENCE ON HIGHLY ANOMALOUS ARCTIC WARMTH DURING NOVEMBER-DECEMBER 2016: According to CMIP5 simulations, the highly anomalous Arctic warmth during November-December 2016, as estimated in five observed datasets, most likely would not have been possible without anthropogenic forcing

Author

Kam, Jonghun, Knutson, Thomas R., Zeng, Fanrong, and Wittenberg, Andrew T.

Subjects
Global warming -- Observations -- Models, Climate models -- Usage, Human-environment interactions -- Environmental aspects, Business, Earth sciences
Abstract

Introduction. Arctic surface temperatures during November-December 2016 were anomalously warm (Fig. 7.1a). An Arctic area-averaged temperature index (Fig. 7.1b and Fig. ES7.2) set a new high record in the GISS [...]

Published
2018

31. 3. CMIP5 MODEL-BASED ASSESSMENT OF ANTHROPOGENIC INFLUENCE ON RECORD GLOBAL WARMTH DURING 2016

Author

Knutson, Thomas R., Kam, Jonghun, Zeng, Fanrong, and Wittenberg, Andrew T.

Subjects
Global warming -- Research, Meteorological research, Climate models -- Usage, Human-environment interactions -- Models -- Research, Business, Earth sciences
Abstract

According to CMIP5 simulations, the 2016 record global warmth was only possible due to substantial centennial-scale anthropogenic warming. Natural variability made a smaller contribution to the JanuaryDecember 2016 annual-mean global [...]

Published
2018
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32. 4. THE EXTREME 2015/16 EL NINO, IN THE CONTEXT OF HISTORICAL CLIMATE VARIABILITY AND CHANGE

Author

Newman, Matthew, Wittenberg, Andrew T., Cheng, Linyin, Compo, Gilbert P., and Smith, Catherine A.

Subjects
Precipitation variability -- Research, Meteorological research -- Research, Business, Earth sciences
Abstract

Record warm central equatorial Pacific Ocean temperatures during the 2015/16 El Nino appear to partly reflect an anthropogenically forced trend. Whether they reflect changes in El Nino variability remains uncertain. [...]

Published
2018
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33. El Niño–Southern Oscillation complexity

Author

Timmermann, Axel, An, Soon-Il, Kug, Jong-Seong, Jin, Fei-Fei, Cai, Wenju, Capotondi, Antonietta, Cobb, Kim M., Lengaigne, Matthieu, McPhaden, Michael J., Stuecker, Malte F., Stein, Karl, Wittenberg, Andrew T., Yun, Kyung-Sook, Bayr, Tobias, Chen, Han-Ching, Chikamoto, Yoshimitsu, Dewitte, Boris, Dommenget, Dietmar, Grothe, Pamela, Guilyardi, Eric, Ham, Yoo-Geun, Hayashi, Michiya, Ineson, Sarah, Kang, Daehyun, Kim, Sunyong, Kim, WonMoo, Lee, June-Yi, Li, Tim, Luo, Jing-Jia, McGregor, Shayne, Planton, Yann, Power, Scott, Rashid, Harun, Ren, Hong-Li, Santoso, Agus, Takahashi, Ken, Todd, Alexander, Wang, Guomin, Wang, Guojian, Xie, Ruihuang, Yang, Woo-Hyun, Yeh, Sang-Wook, Yoon, Jinho, Zeller, Elke, and Zhang, Xuebin

Published
2018
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40. On the Genesis of the 2021 Atlantic Niño.

Author

Lee, Sang‐Ki, Lopez, Hosmay, Tuchen, Franz Philip, Kim, Dongmin, Foltz, Gregory R., and Wittenberg, Andrew T.

Subjects
EL Nino, OCEAN waves, WESTERLIES, OCEAN temperature, MADDEN-Julian oscillation, ROSSBY waves, THUNDERSTORMS
Abstract

An extreme Atlantic Niño developed in the boreal summer of 2021 with peak‐season sea surface temperature anomalies exceeding 1°C in the eastern equatorial region for the first time since global satellite measurements began in the early 1970s. Here, we show that the development of this outlier event was preconditioned by a series of oceanic Rossby waves that reflected at the South American coast into downwelling equatorial Kelvin waves. In early May, an intense week‐long westerly wind burst (WWB) event, driven by the Madden‐Julian Oscillation (MJO), developed in the western and central equatorial Atlantic and greatly amplified one of the reflected Kelvin waves, directly initiating the 2021 Atlantic Niño. MJO‐driven WWBs are fundamental to the development of El Niño in the Pacific but are a previously unidentified driver for Atlantic Niño. Their importance for the 2021 event suggests that they may serve as a useful predictor/precursor for future Atlantic Niño events. Plain Language Summary: Atlantic Niño is the Atlantic counterpart of El Niño in the Pacific, often referred to as El Niño's little brother. It was previously thought to have only regional influence on rainfall variability in West Africa, but a growing number of studies have shown that Atlantic Niño also plays an important role in the development of El Niño–Southern Oscillation, as well as in the formation of powerful hurricanes near the coast of West Africa. This study investigates the development of an extreme Atlantic Niño in the summer of 2021. Here, we show that the 2021 event was preconditioned by warm waters piled up near the South American coast, and then directly triggered by a westerly wind burst event that drove the warm waters eastward. The westerly wind burst event was driven by a patch of tropical thunderstorms that formed across the Indian Ocean and moved slowly eastward across the Pacific, South America, and the Atlantic, also known as the Madden‐Julian Oscillation. Westerly wind bursts driven by the Madden‐Julian Oscillation are fundamental for the development of El Niño in the Pacific, but a previously unidentified driver for Atlantic Niño, and thus may improve our ability to predict future Atlantic Niño events. Key Points: The extreme 2021 Atlantic Niño was preconditioned by a series of oceanic Rossby waves reflected into downwelling equatorial Kelvin wavesOne of the Kelvin waves was greatly amplified by an intense week‐long westerly wind burst event, initiating the 2021 Atlantic NiñoThe westerly wind burst was driven by the Madden‐Julian Oscillation, which is a previously unidentified driver for Atlantic Niño [ABSTRACT FROM AUTHOR]

Published
2023
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41. Observing and predicting the 2015/16 El Nino

Author

L'Heureux, Michelle L., Takahashi, Ken, Watkins, Andrew B., Barnston, Anthony G., Becker, Emily J., Liberto, Tom E. Di, Gamble, Felicity, Gottschalck, Jon, Halpert, Michael S., Huang, Boyin, Mosquera-VAsquez, Kobi, and Wittenberg, Andrew T.

Subjects
Numerical weather forecasting -- Methods -- Environmental aspects, Southern oscillation -- Environmental aspects -- Methods, Business, Earth sciences
Abstract

ABSTRACT The El Nino of 2015/16 was among the strongest El Nino events observed since 1950 and took place almost two decades after the previous major event in 1997/98. Here, [...]

Published
2017
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42. UNDERSTANDING ENSO DIVERSITY

Author

Capotondi, Antonietta, Wittenberg, Andrew T., Newmaman, Matthew, Di Lorenzo, Emamanuele, Yu, Jin-Yi, Braconnot, Pascacale, Cole, Julia, Dewitte, Boris, Giese, Benjamin, Guilyardi, Eric, Jin, Fei-Fei, Karnauskas, Kristopher, Kirtman, Benjamin, Lee, Tong, Schneider, Niklas, Xue, Yan, and Yeh, Sang-Wook

Published
2015

50. Resolving the Tropical Pacific/Atlantic Interaction Conundrum.

Author

Jiang, Feng, Zhang, Wenjun, Jin, Fei‐Fei, Stuecker, Malte F., Timmermann, Axel, McPhaden, Michael J., Boucharel, Julien, and Wittenberg, Andrew T.

Subjects
CLIMATE change, EL Nino, OCEAN temperature, SOUTHERN oscillation, COMMUNITIES
Abstract

Understanding the interaction between the tropical Pacific and Atlantic Oceans has challenged the climate community for decades. Typically, boreal summer Atlantic Niño events are followed by vigorous Pacific events of opposite sign around two seasons later. However, incorporating the equatorial Atlantic information to variabilities internal to the Pacific lends no significant additional predictive skill for the subsequent El Niño‐Southern Oscillation (ENSO). Here we resolve this conundrum in a physically consistent frame, in which the nascent onset of a Pacific event rapidly induces an opposite‐signed summer equatorial Atlantic event and the lead correlation of Atlantic over Pacific is a statistical artifact of ENSO's autocorrelation. This Pacific‐to‐Atlantic impact is limited to a short window around late spring due to seasonally‐amplified Atlantic atmosphere‐ocean coupling. This new frame reconciles the discrepancies between the observed and multi‐model simulated inter‐basin relationship, providing a major advance in understanding seasonally‐modulated inter‐basin climate connections as well as their predictability. Plain Language Summary: Previous studies interpreted the observed lead/lag relationship between Atlantic Niño/Niña and Pacific Niño/Niña sea surface temperature anomalies as evidence for a precursory role of the equatorial Atlantic on the development of El Niño–Southern Oscillation (ENSO) events. This study clearly demonstrates that this statistical relationship is not related to Atlantic‐to‐Pacific causality, but can rather be explained by seasonally modulated equatorial Atlantic's response to ENSO. We find that Pacific ENSO events drive equatorial Atlantic events rather than vice versa, and reconcile the apparent discrepancies between the observed and multi‐model simulated tropical Pacific/Atlantic relationship. Key Points: The lead correlation of the equatorial Atlantic over the Pacific is not related to Atlantic‐to‐Pacific causalityThe tropical Pacific/Atlantic interaction is consistent with the nascent onset of Pacific events driving the equatorial Atlantic eventsThe discrepancies between the observed and multi‐model simulated tropical Pacific/Atlantic relationship can be reconciled in this new frame [ABSTRACT FROM AUTHOR]

Published
2023
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