Contributions of Arctic Sea‐Ice Loss and East Siberian Atmospheric Blocking to 2020 Record‐Breaking Meiyu‐Baiu Rainfall
Heavy Meiyu‐Baiu rainfall occurred over central‐east China and Japan in June–July 2020. This study analyzes observational and reanalysis data and performs atmospheric model simulations to investigate its causes. It is found that low Arctic sea ice cover (SIC) in late spring‐early summer of 2020 alon...
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| Published in: | Geophysical research letters 2021-05, Vol.48 (10), p.n/a |
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| Main Authors: | , , , |
| Format: | Article |
| Language: | eng |
| Subjects: | |
| Online Access: | Request full text |
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| Summary: | Heavy Meiyu‐Baiu rainfall occurred over central‐east China and Japan in June–July 2020. This study analyzes observational and reanalysis data and performs atmospheric model simulations to investigate its causes. It is found that low Arctic sea ice cover (SIC) in late spring‐early summer of 2020 along the Siberian coast was an important factor. The low SIC caused local warming and high pressure, resulted in excessive atmospheric blockings over East Siberia, which caused cold air outbreaks into the Meiyu‐Baiu region, stopped the seasonal northward march of the Meiyu‐Baiu front, and increased the thermal contrast across the front, leading to record‐breaking rainfall in June–July 2020. Our results suggest that the 2020 extreme Meiyu‐Baiu was partly caused by the low SIC around the Siberian coast through its impact on East Siberian blockings. As sea ice along the Siberian coast decreases under global warming, its variations and thus influence on Meiyu‐Baiu rainfall may weaken.
Plain Language Summary
Meiyu‐Baiu, a west—east oriented stationary front from central‐east China to Japan, usually persists from mid‐June to mid‐July. In June–July 2020, central‐east China and Japan encountered record‐breaking Meiyu‐Baiu rainfall. Through analyses of observational and reanalysis data, we found that excessive East Siberian atmospheric blockings—large‐scale quasi‐stationary anticyclonic circulations—during the 2020 Meiyu‐Baiu season increased cold air outbreaks into the Meiyu‐Baiu region, stopped the northward march of the Meiyu‐Baiu front, and enhanced the temperature contrast across the front, leading to record‐breaking Meiyu‐Baiu rainfall in 2020. Using atmospheric model experiments, we further show that the frequent East Siberian blockings can be largely attributed to excessive sea ice melting and the concurring warming along the Siberian coast. The lower‐atmospheric warming reduced local meridional temperature gradients and zonal winds, which favors East Siberian blockings. Our results highlight the effect of Arctic sea ice decline and the associated warming on Meiyu‐Baiu rainfall and provide a new mechanism for the Arctic to affect mid‐latitude precipitation in late spring‐early summer. This Arctic effect may change in the future as late spring‐early summer sea ice diminishes under global warming.
Key Points
The excessive atmospheric blockings over East Siberia enhanced the Meiyu‐Baiu rainfall in June–July 2020
The low Arctic sea ice favored East Siberian blockings an |
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| ISSN: | 0094-8276 1944-8007 |