Contributions of Arctic Sea‐Ice Loss and East Siberian Atmospheric Blocking to 2020 Record‐Breaking Meiyu‐Baiu Rainfall

Chen, Xiaodan; Dai, Aiguo; Wen, Zhiping; Song, Yuanyuan

doi:10.1029/2021gl092748

Cited by 37 publications

(27 citation statements)

References 41 publications

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“…The S2S forecasting systems' features vary greatly among the models: dynamic framework, assimilation strategy, and more importantly, whether the systems directly assimilate sea ice concentration from the observations (e.g., the CMA versus the ECMWF and JMA). In particular, the Arctic Sea ice alters the mid-latitude variations and thus influences the 2020 record-breaking mei-yu (e.g., Chen et al 2021). Considering the great diversity in handling the sea ice, what impact it may have on the mei-yu forecast in some specific S2S models need further investigation in the future.…”

Section: Summary and Discussionmentioning

confidence: 99%

Subseasonal forecast barrier of the North Atlantic oscillation in S2S models during the extreme mei-yu rainfall event in 2020

et al. 2021

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Enhanced predictability of high-impact weather events is a Subseasonal to Seasonal Prediction Project (S2S) priority. In early summer 2020, a record-breaking heavy rainfall event occurred over the Yangtze River valley during the mei-yu season (June and July). Here we evaluate the S2S model forecast performance concerning the summer 2020 extreme mei-yu event over the Yangtze River valley. Our results show all operational S2S models exhibit fluctuating high-low-high forecast skill patterns during this three-stage mei-yu event, determined by different dominant circulations. In particular, the poor midlatitude circulation forecast (low trough over northern China) in the North Atlantic Oscillation (NAO) negative phase, with relative more contribution than that of the low-latitude circulation (western North Pacific subtropical high and South Asian high), decreases the model forecast skill for mei-yu rainfall in early-mid July. The prediction barrier of the NAO pattern and its downstream response, via the eastward-propagating wave train, jointly decrease the rainfall forecast skill during the NAO active negative period. Therefore, the skillful model prediction of the active summer NAO could help predict mei-yu events in the East Asian summer monsoon, suggesting further model improvements to the S2S forecasting of summertime mid-latitude variations are urgently needed.

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Section: Summary and Discussionmentioning

confidence: 99%

Subseasonal forecast barrier of the North Atlantic oscillation in S2S models during the extreme mei-yu rainfall event in 2020

et al. 2021

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“…The precipitation events are controlled mainly by other factors, such as the onset/peak/withdrawal period of BCM front and typhoon activities. According to a recent study, the occurrence of blocking in high latitudes led to stopping the northward march of the BCM front, leading to record‐breaking BCM rainfall in June–July 2020 (Chen et al ., 2021). This suggests that further studies are needed to investigate the combined influence of the OKB and BCM front activities on precipitation over South Korea.…”

Section: Discussionmentioning

confidence: 99%

Influence of Okhotsk Sea blocking on summer precipitation over South Korea

Song

Ahn

2021

Intl Journal of Climatology

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This study examined the influence of atmospheric blocking on the variability of precipitation over South Korea during summer (June–July–August) by defining the blocking frequency over the Okhotsk Sea (Okhotsk Sea blocking frequency; OK_BF). According to composite analysis for the years of high precipitation over South Korea, blocking occurs more frequently over the Okhotsk Sea (140°E–160°E). Partial correlation and regression analyses were conducted to separate the contribution of OK_BF to precipitation variability from that of the low‐level meridional wind (LLMW) because LLMW over the region is another important aspect of summer precipitation in South Korea. The barotropic structures of positive geopotential height anomalies over the Okhotsk Sea associated with increasing OK_BF can induce negative temperature anomalies over South Korea due mainly to the equatorward advection of cold air masses from higher latitudes. The enhanced meridional temperature gradient can cause increases in baroclinic instability and zonal wind vertical shear according to the thermal wind balance. This instability can induce anomalous cyclonic circulations over South Korea, resulting in positive precipitation anomalies. The partial correlation coefficients (R2 = 0.35–0.40) between the OK_BF and precipitation indices, including mean precipitation, extreme precipitation intensity, wet days, and consecutive wet days, were all statistically significant at the 95% confidence level. Overall, the effects of the increasing OK_BF on both precipitation and potential evapotranspiration can intensify the surface water budget in South Korea.

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“…These studies found that the stable western Pacific subtropical high (WPSH) and strong Asian subtropical westerly jet (ASWJ) , Zhao et al 2022 were two factors that influenced directly the rainfall. The atmospheric circulation anomalies that contributed to the record-breaking rainfall in summer 2020 are believed to have been modulated by sea surface temperature anomalies in the Indian Ocean (Cai et al 2022, Zhou et al 2021 and tropical Pacific , Pan et al 2021, Chu et al 2022, the North Atlantic Oscillation (Liu et al 2020), active potential vorticity over the Tibetan Plateau (Ma et al 2022a), the Madden-Julian Oscillation (Liang et al 2021), and the Arctic seaice extent (Chen et al 2021). Obviously, the above research focused mainly on the impact of natural variability on record-breaking rainfall.…”

Section: Introductionmentioning

confidence: 99%

Record-breaking summer rainfall in the Asia–Pacific region attributed to the strongest Asian westerly jet related to aerosol reduction during COVID-19

Chen

Zhang

et al. 2023

Environ. Res. Lett.

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The Asia–Pacific region suffered record rainfall in summer 2020, which was accompanied by the strongest Asian subtropical westerly jet (ASWJ) of the past four decades. Meanwhile, the COVID-19 pandemic spread rapidly around the world, resulting in an abrupt reduction in emissions in East Asia. Here, we investigate whether the enhanced ASWJ induced by plummeting aerosols contributed to the record-breaking rainfall. The results show that tropospheric warming in Southeast Asia, in particular southern China, due to local aerosol reduction, acted to increase the meridional temperature gradients in the mid−lower troposphere, which supported a strong ASWJ in the upper troposphere via the thermal wind balance. The latter enhanced divergence in the upper troposphere over the Asia–Pacific region, which provided a favorable ascending motion for the record rainfall that took place there. Therefore, against a background of carbon neutrality (i.e., the reduction in aerosols), our results imply more strong summer rainfall in the Asia–Pacific region.

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Contributions of Arctic Sea‐Ice Loss and East Siberian Atmospheric Blocking to 2020 Record‐Breaking Meiyu‐Baiu Rainfall

Cited by 37 publications

References 41 publications

Subseasonal forecast barrier of the North Atlantic oscillation in S2S models during the extreme mei-yu rainfall event in 2020

Subseasonal forecast barrier of the North Atlantic oscillation in S2S models during the extreme mei-yu rainfall event in 2020

Influence of Okhotsk Sea blocking on summer precipitation over South Korea

Record-breaking summer rainfall in the Asia–Pacific region attributed to the strongest Asian westerly jet related to aerosol reduction during COVID-19

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