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4. Advances in the Subseasonal Prediction of Extreme Events : Relevant Case Studies across the Globe

Author

Domeisen, Daniela I. V., White, Christopher J., Afargan-Gerstman, Hilla, Muñoz, Ángel G., Janiga, Matthew A., Vitart, Frédéric, Wulff, C. Ole, Antoine, Salomé, Ardilouze, Constantin, Batté, Lauriane, Bloomfield, Hannah C., Brayshaw, David J., Camargo, Suzana J., Charlton-Pérez, Andrew, Collins, Dan, Cowan, Tim, del Mar Chaves, Maria, Ferranti, Laura, Gómez, Rosario, González, Paula L. M., Romero, Carmen González, Infanti, Johnna M., Karozis, Stelios, Kim, Hera, Kolstad, Erik W., LaJoie, Emerson, Lledó, Llorenç, Magnusson, Linus, Malguzzi, Piero, Manrique-Suñén, Andrea, Mastrangelo, Daniele, Materia, Stefano, Medina, Hanoi, Palma, Lluís, Pineda, Luis E., Sfetsos, Athanasios, Son, Seok-Woo, Soret, Albert, Strazzo, Sarah, and Tian, Di

Published
2022

5. Explaining Extreme Events of 2020 from a Climate Perspective

Author

Stone, Dáithí A., Lawal, Kamoru A., Lennard, Chris, Tadross, Mark, Wolski, Piotr, Wehner, Michael F., Hope, Pandora, Zhao, Mei, Abhik, S., Tolhurst, Gen, McKay, Roseanna C., Rauniyar, Surendra P., Bettio, Lynette, Ramchurn, Avijeet, Lim, Eun-Pa, Pepler, Acacia S., Cowan, Tim, Watkins, Andrew B., Barsugli, Joseph J., Easterling, David R., Arndt, Derek S., Coates, David A., Delworth, Thomas L., Hoerling, Martin P., Johnson, Nathaniel, Kapnick, Sarah B., Kumar, Arun, Kunkel, Kenneth E., Schreck, Carl J., Vose, Russell S., Zhang, Tao, Otto, Friederike E. L., Kew, Sarah, Philip, Sjoukje, Stott, Peter, Van Oldenborgh, Geert Jan, Hoell, Andrew, Quan, Xiao-Wei, Hoerling, Martin, Fu, Rong, Mankin, Justin, Simpson, Isla, Seager, Richard, He, Cenlin, Lehner, Flavio, Lisonbee, Joel, Livneh, Ben, Sheffield, Amanda, Christidis, Nikolaos, Stott, Peter A., Kam, Jonghun, Min, Seung-Ki, Kim, Yeon-Hee, Kim, Byeong-Hee, Kug, Jong-Seong, Liu, Zhongwei, Eden, Jonathan M., Dieppois, Bastien, Drobyshev, Igor, Gallo, Carolina, Blackett, Matthew, Liu, Yujia, Li, Chao, Sun, Ying, Zwiers, Francis, Zhang, Xuebin, Jiang, Zhihong, Zheng, Fei, Pei, Lin, Yan, Zhongwei, Chen, Deliang, Miao, Shiguang, Yu, Hongyong, Yu, Xiaojing, Zhou, Ziwei, Wang, Yu, Li, Yingxin, Nanding, Nergui, Freychet, Nicolas, Dong, Buwen, Wang, Dongqian, Lott, Fraser C., Tett, Simon F. B., Sparrow, Sarah, Du, Jizeng, Fu, Kaiqi, Wang, Kaicun, Cui, Baoshan, Ma, Yuanyuan, Hu, Zhiyuan, Meng, Xianhong, Liu, Fei, Dong, Wenjie, Tang, Haosu, Wang, Ziyue, Tang, Bin, Ma, Yayu, Tian, Fangxing, Wang, Jun, Jo, Seo-Young, Seong, Min-Gyu, Son, Seok-Woo, Byun, Young-Hwa, Lu, Chunhui, Tradowsky, Jordis S., Bird, Leroy, Kreft, Peter V., Rosier, Suzanne M., Soltanzadeh, Iman, Bodeker, Greg E., Qian, Cheng, Ye, Yangbo, Zhang, Wenxia, Zhou, Tianjun, Kawase, Hiroaki, Watanabe, Shunichi, Hirockawa, Yasutaka, Imada, Yukiko, Luo, Fu, Wang, Shanshan, He, Yongli, Wang, Yanxin, and Wang, Hao

Published
2022

11. Asian Anthropogenic Aerosol Forcing Played a Key Role in the Multidecadal Increase in Australian Summer Monsoon Rainfall

Author

Fahrenbach, Nora L. S., Bollasina, Massimo A., Samset, Bjorn H., Cowan, Tim, Ekman, Annica M. L., Fahrenbach, Nora L. S., Bollasina, Massimo A., Samset, Bjorn H., Cowan, Tim, and Ekman, Annica M. L.

Abstract

Observations show a significant increase in Australian summer monsoon (AUSM) rainfall since the mid-twentieth century. Yet the drivers of this trend, including the role of anthropogenic aerosols, remain uncertain. We addressed this knowledge gap using historical simulations from a suite of Coupled Model Intercomparison Project phase 6 (CMIP6) models, the CESM2 Large Ensemble, and idealized single-forcing simulations from the Precipitation Driver Response Model Intercomparison Project (PDRMIP). Our results suggest that Asian anthropogenic aerosol emissions played a key role in the observed increase in AUSM rainfall from 1930 to 2014, alongside the influence of internal variability. Sulfate aerosol emissions over Asia led to regional surface cooling and strengthening of the climatological Siberian high over eastern China, which altered the meridional temperature and sea level pressure gradients across the Indian Ocean. This caused an intensification and southward shift of the Australian monsoonal westerlies (and the local Hadley cell) and resulted in a precipitation increase over northern Australia. Conversely, the influence of increased greenhouse gas concentrations on AUSM rainfall was minimal due to the compensation between thermodynamically induced wettening and transient eddy-induced drying trends. At a larger scale, aerosol and greenhouse gas forcing played a key role in the climate response over the Indo-Pacific sector and eastern equatorial Pacific, respectively (coined the tropical Pacific east- west divide). These findings contribute to an improved understanding of the drivers of the multidecadal trend in AUSM rainfall and highlight the need to reduce uncertainties in future projections under different aerosol emission trajectories, which is particularly important for northern Australia's agriculture.

Published
2024
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22. Evaluation of the HadGEM3-A simulations in view of detection and attribution of human influence on extreme events in Europe

Author

Vautard, Robert, Christidis, Nikolaos, Ciavarella, Andrew, Alvarez-Castro, Carmen, Bellprat, Omar, Christiansen, Bo, Colfescu, Ioana, Cowan, Tim, Doblas-Reyes, Francisco, Eden, Jonathan, Hauser, Mathias, Hegerl, Gabriele, Hempelmann, Nils, Klehmet, Katharina, Lott, Fraser, Nangini, Cathy, Orth, René, Radanovics, Sabine, Seneviratne, Sonia I., van Oldenborgh, Geert Jan, Stott, Peter, Tett, Simon, Wilcox, Laura, and Yiou, Pascal

Published
2019
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49. Skill of ACCESS-S2 in predicting rainfall bursts over Australia

Author

Cowan, Tim, Wheeler, Matthew C., Hudson, Debra, de Burgh-Day, Catherine, Griffiths, Morwenna, Young, Griffith, Cowan, Tim, Wheeler, Matthew C., Hudson, Debra, de Burgh-Day, Catherine, Griffiths, Morwenna, and Young, Griffith

Abstract

Precipitation falling in multi-day bursts is an important water source for the northern Australian tropics in summer and southern Australia in the cool autumn and winter months. Primary producers of crops and livestock need to plan for these events beyond the 7-day deterministic timeframe during the northern wet season (October – April) and southern wet season (April – November), to aid in their business operations. To coincide with the operational release of a multi-week burst potential forecast product in mid-2022, this report examines the skill of the Bureau's latest sub-seasonal-to-seasonal forecast system, the Australian Community Climate Earth-System Simulator – Seasonal version 2 (ACCESS-S2), released in October 2021, in predicting burst events 1 to 4 weeks in advance, predominantly focusing on northern Australia. We use the Symmetric Extremal Dependence Index (SEDI) as a metric to evaluate the skill of ACCESS-S2 in predicting rainfall bursts, given these are often rare events, particularly throughout the rangelands and sub-arid regions of northern Australia. As well as evaluating the hindcast skill of ACCESS-S2, we also apply the SEDI score to ACCESS-S1, to assess if there has been an appreciable improvement in burst prediction skill between forecast system versions. As expected, the skill of ACCESS-S2 in predicting rainfall bursts across northern Australia (north of 30°S) is highest in the first week of the forecast and decreases with lead time. Skill is generally stronger and more significant over Queensland than the Northern Territory and northern Western Australia in the second week of the forecast between October to December. The peak skill months, in terms of magnitude and area of significance, occur from January to March, with the highest skill scores in March across all lead times (weeks 1 to 4). The ACCESS-S2 forecast system is also more skilful at predicting lower threshold bursts (e.g., 20 or 30 mm in 3-day events) than the more extreme, rarer bur

Published
2022

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