Abstract
An observed fact is proposed that the 2020 record-breaking Meiyu over the Yangtze–Huaihe River Basin (YHRB) is characteristic of significant subseasonal variation. The anomalously enhanced rainfall experiences a southward retreat from the northern YHRB in June to the southern YHRB in July. The meridional shift of abnormal rainbelt is closely related to the different anomalous Meiyu front circulations. The first stage features a warm Meiyu front with an extremely strong northward transport of warm-and-wet air, whereas a cold front forms with a convergence between the strong northeasterlies and southwesterlies in July. Another significant subseasonal variation of the 2020 Meiyu is that the Meiyu rainfall evolves in a periodic quasi-biweekly oscillation (QBWO). On the scale of the QBWO, the cold air activities over East Asia contribute significantly to Meiyu; each intense southward invasion of cold air corresponds well to the enhancement of Meiyu rainfall. However, the location of the western Pacific subtropical high, the subtropical East Asia summer monsoon (SEASM), and the intensity of the East Asia subtropical westerly jet exhibit opposite QBWO characteristics in June and July. For an increasing (decreasing) of Meiyu rainfall, the western Pacific subtropical high marches northward (retreats southward), the subtropical East Asia summer monsoon weakens (strengthens), and the East Asia subtropical westerly jet accelerates (decelerates) in June. The opposite holds true in July. Further analyses reveal that the filtered cyclone over Northeast China benefiting the southward intrusion of cold air is associated with the eastward propagation of a wave train over the mid-high latitudes in June, whereas it arises from both the westward propagation of a wave train over the mid-high latitudes and the northward propagation of cyclonic circulation from the tropics in July.
Highlights
Severe rainstorms and devastating floods severely hit southern Japan and the Yangtze–Huaihe River Basins (YHRB) in China in the early summer of 2020
Persistent rainfall accompanied with frequent heavy rainstorms brings a record-broking Meiyu event and causes devastating floods over the YHRB
The Meiyu rainfall is closely related to the anomalous East Asia summer monsoon (EASM) atmospheric circulation systems with westward and northward western Pacific subtropical high (WPSH), evident expansion of the East Asia subtropical westerly jet (EASWJ) and South Asian High (SAH), and the accelerated lower-level southwesterly flows
Summary
Severe rainstorms and devastating floods severely hit southern Japan and the Yangtze–Huaihe River Basins (YHRB) in China in the early summer of 2020. The rainy period is the well-known Meiyu in China ( called Baiu in Japan and Changma in Korea), a typical episode in the progression of East Asia summer monsoon (EASM) (Tao and Chen, 1987; Yihui and Chan, 2005). Meiyu starts in mid-June and ends in mid-July. By the monitoring of China National Climate Center, 2020 Meiyu persists from June 1 to August 1 with an earlier onset and a later ending. The long duration and the accumulated Meiyu precipitation around the Yangtze River Basins both broke the record since 1961 (Gan, 2020; Ding et al, 2021). The anomalously enhanced Meiyu precipitation causes great losses of life and property
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
