MJO Phase Swings Modulate the Recurring Latitudinal Shifts of the 2020 Extreme Summer‐Monsoon Rainfall Around Yangtse

Wang, Yuwen; Ren, Hong‐Li; Wei, Yuntao; Jin, Fei‐Fei; Ren, Pengfei; Gao, Li; Wu, Jie

doi:10.1029/2021jd036011

Cited by 11 publications

(7 citation statements)

References 50 publications

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“…Hydroclimate extremes driven by the ASM are no exception and may change in a warming climate (Rajesh & Goswami, 2022; Saranya et al., 2022; Sarkar & Maity, 2022). Both strong and weak monsoons have the potential to critically disrupt agriculture, damage infrastructure via flooding, and impact water supply (Wang et al., 2022). Generating a more robust understanding of future hydroclimate extremes in the ASM region depends on accurate statistics surrounding the role of natural variability in modulating rainfall.…”

Section: Discussionmentioning

confidence: 99%

“…

The Asian summer monsoon (ASM) supplies freshwater resources for nearly 4 billion people annually. Its variations and related hydroclimate events cause floods and droughts, which have far-reaching social and economic impacts, especially in countries that are heavily dependent on agriculture (Gadgil & Kumar, 2006;Loo et al, 2015;Wang et al, 2022). Climate change is expected to change the characteristics of the ASM (Rajesh & Goswami, 2022); dry and hot monsoon extremes are expected to occur more frequently alongside future warming (Mishra et al, 2020), in addition to the increased risk of flash flooding (Almazroui et al, 2021).

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confidence: 99%

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Tropical Pacific Modulation of the Asian Summer Monsoon Over the Last Millennium in Paleoclimate Data Assimilation Reconstructions

Hu,

Dee,

Parajuli

et al. 2023

JGR Atmospheres

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Large uncertainties exist in climate model projections of the Asian Summer Monsoon (ASM). Whereas the El Niño‐Southern Oscillation (ENSO) is an important modulator of the ASM, the ENSO‐ASM teleconnection is not stationary. Furthermore, teleconnections between ENSO and the East Asian versus South Asian subcomponents of the ASM exhibit distinct characteristics. Therefore, understanding the variability of the ENSO‐ASM teleconnection is critical for anticipating future variations in ASM intensity. To this end, we use paleoclimate records to extend temporal coverage beyond the instrumental era by millennia. Recently, data assimilation techniques have been applied for the last millennium, which facilitates physically consistent, globally‐gridded climate reconstructions informed by paleoclimate observations. We use these novel data assimilation products to investigate variations in the ENSO‐ASM relationship over the last 1000 years. We find that correlations between ENSO and ASM indices are mostly negative in the last millennium, suggesting that strong ASM years are often associated with La Niña events. During periods of weak correlations between ENSO and the East Asian summer monsoon, we observe an El Niño‐like sea surface temperature (SST) pattern in the Pacific. Additionally, SST patterns associated with periods of weak correlations between ENSO and South Asian summer monsoon rainfall are not consistent among data assimilation products. This underscores the importance of developing more precipitation‐sensitive paleoclimate proxies in the Indian subcontinental realm over the last millennium. Our study serves as a baseline for future appraisals of paleoclimate assimilation products and an example of informing our understanding of decadal‐scale ENSO‐ASM teleconnection variability using paleoclimate datasets.

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Section: Discussionmentioning

confidence: 99%

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mentioning

confidence: 99%

Tropical Pacific Modulation of the Asian Summer Monsoon Over the Last Millennium in Paleoclimate Data Assimilation Reconstructions

Hu,

Dee,

Parajuli

et al. 2023

JGR Atmospheres

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“…Particularly in July 2020, the long-standing MJO in the Indian Ocean favored the WNP anomalous low-level anticyclone (e.g., Gong et al, 2022) but this is not the case for June. Wang et al (2022) noted that the convective episode associated with MJO in July slowly propagated eastward and decayed when encountering the Maritime Continent barrier effect (Zhang & Ling, 2017). This event comes under the non-propagating MJO convection event (Kim et al, 2014).…”

Section: Changes In Sst and Low-level Circulationmentioning

confidence: 99%

“…suggested that an unprecedented long-standing MJO occurred in the Indian Ocean during early summer. Wang et al (2022) showed that the MJO had modulated the latitudinal position and intensity of the anomalous anticyclone over the WNP. Particularly in July 2020, the long-standing MJO in the Indian Ocean favored the WNP anomalous low-level anticyclone (e.g., Gong et al, 2022) but this is not the case for June.…”

Section: Changes In Sst and Low-level Circulationmentioning

confidence: 99%

Unusual subseasonal variability of Indian summer monsoon rainfall in 2020

Darshana,

Chowdary,

Parekh

et al. 2024

Quart J Royal Meteoro Soc

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Above‐normal all‐India summer monsoon (ISM) rainfall was received in 2020 with 109% of its long‐period average. According to the India Meteorological Department (IMD), ISM 2020 experienced robust month‐to‐month rainfall variations; in particular, the peak monsoon month of July 2020 witnessed deficit rainfall. The present study investigated the possible mechanisms that are responsible for the July 2020 deficit rainfall. Analysis revealed that the strong low‐level moisture divergence caused by the westward‐propagating atmospheric Rossby wave, induced by suppressed western North Pacific (WNP) convection, is primarily responsible for the July rainfall deficit. The WNP suppressed convection is linked to anomalous low‐level anticyclonic circulation. It is noted that the intense WNP anticyclone is maintained by the tropical Indian Ocean (TIO) warming‐induced atmospheric Kelvin waves and strong low‐level convergence over the Meiyu‐Baiu rainband. Unlike July, the strength of the WNP anticyclone and TIO warming are weaker in June and August. In addition to the observational analysis, the skill of the Climate Forecast System version‐2 (CFSv2) model in predicting the July rainfall at a lead of about two months is examined. Strong positive rainfall anomalies over India are predicted by the model in July, which is in contrast to the observations. Despite predicting the TIO warming, the model failed to capture the westward extension of the WNP anticyclone, which impacted the July rainfall prediction. To understand the importance of the WNP anticyclone on ISM rainfall, a CFSv2 sensitivity experiment is carried out by imposing strong negative sea surface temperature (SST) anomalies over the WNP region to excite the anticyclone. Both the westward extension of the WNP anticyclone and suppressed rainfall over the core monsoon region in July are captured by the model when low‐level circulation is imposed. The model sensitivity experiment strongly supports the role of the WNP anticyclone and its westward extension in inducing reduced rainfall in July 2020 over the monsoon trough region.

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“…The convection and upper‐tropospheric divergence of MJO activities also act as a Rossby wave source and stimulate the teleconnection between Tropics and mid‐latitudes on an intraseasonal timescale. In addition, they can further modulate the modes of extratropical climate variability and weather patterns, such as the North Atlantic Oscillation, Pacific‐North American pattern, blockings and extreme flooding and drought events (Stan et al ., 2017; Li et al ., 2020; Wang et al ., 2022). Due to its periodic nature and significant impacts, the MJO is a primary predictability source on a subseasonal timescale (Merryfield et al ., 2020) and provides windows of opportunity for skilful predictions during its active periods (Mariotti et al ., 2020).…”

Section: Introductionmentioning

confidence: 99%

Climatological diagnostics and subseasonal‐to‐seasonal predictions of Madden–Julian Oscillation events

Ren

Jia

et al. 2023

Intl Journal of Climatology

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The Madden–Julian Oscillation (MJO) is the dominant mode of tropical intraseasonal variability, which serves as a primary source of subseasonal‐to‐seasonal (S2S) predictability. Noticeably, MJO is not always a regularly recurring cycle but is characterized by discrete episodes. In this study, considering the quasi‐consecutive actives and eastward propagating features, a standard metric is proposed to identify MJO events based on the real‐time multivariate MJO (RMM) index. The re‐identification of historical MJO events reveals that there were 5.4 MJO events each year since 1981, and the average duration of each event is about 31.5 days. More MJO events tend to occur in the boreal winter and spring, with stronger intensity, longer duration and faster propagating speed than those in the boreal summer. Furthermore, MJO events are more likely to initiate in Phases 2 and 5, with a longer lifetime than those initiating in other phases. The amplitude and propagation characteristics of MJO events are strongly modulated by the dominant modes of sea surface temperature interannual variability with a strong regional dependence. Based on hindcast datasets of six S2S models, the prediction skill for the MJO is evaluated in the perspective of individual events. The longest leading time of the skilful prediction for individual MJO events ranges from 11 to 17 days, far below the traditional recognition. This result could be attributed to the apparent prediction barrier of MJO initiation, that is, a rapid decrease in prediction skill when predictions are carried out before the initiation of MJO events. In addition, the prediction skills of MJO events depends on interannual variabilities, with relatively higher skills under the conditions of the El Niño and Indian Ocean basin warming. These findings may shed light on the complexity and challenges of profoundly understanding and skilfully predicting MJO events.

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MJO Phase Swings Modulate the Recurring Latitudinal Shifts of the 2020 Extreme Summer‐Monsoon Rainfall Around Yangtse

Cited by 11 publications

References 50 publications

Tropical Pacific Modulation of the Asian Summer Monsoon Over the Last Millennium in Paleoclimate Data Assimilation Reconstructions

Tropical Pacific Modulation of the Asian Summer Monsoon Over the Last Millennium in Paleoclimate Data Assimilation Reconstructions

Unusual subseasonal variability of Indian summer monsoon rainfall in 2020

Climatological diagnostics and subseasonal‐to‐seasonal predictions of Madden–Julian Oscillation events

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