Comparative Analysis of Atmospheric Circulation of Persistent Heavy Rainfall in Middle and Low Reaches of Yangtze River between 1998 and 2017

Based on observation data supplied by the Chinese Meteorological Administration (CMA) and reanalysis datasets provided by the ECMWF, the multiscale causes of persistent heavy rainfall events (PHREs) that occurred from 1979 to 2018 during Meiyu periods over the middle and lower reaches of the Yangtze River (MLYR) are investigated. During Meiyu periods, precipitation shows obvious interannual variabilities. In PHRE years, the contribution rate of persistent heavy rainfall to the total precipitation is approximately 57%. Precipitation also shows significant synoptic-scale (less than 10 days) characteristics. Through the quantitative diagnosis of interactions among background-scale (greater than 30 days), quasi-biweekly-scale (10–30-days), and synoptic-scale variables, the possible causes of PHREs are explored. The results reveal that the difference in precipitation intensity between PHRE years and non-PHRE years is determined by the background water vapor, background wind and synoptic-scale wind conditions. In PHRE years, the prevailing background southwesterly winds from lower latitudes provide more background water vapor, and more mean kinetic energy is converted to perturbation energy. Moreover, the active synoptic-scale oscillations from higher latitudes and the convergence of Rossby wave disturbance energy over the MLYR could also cause the occurrence and maintenance of PHREs during Meiyu periods. The multiscale causes and corresponding circulation patterns in 2020 PHREs are similar to PHREs years.

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Decadal and Interannual Variability of Persistent Heavy Rainfall Events over the Middle and Lower Reaches of the Yangtze River Valley

Journal of Meteorological Research ◽

10.1007/s13351-019-9070-5 ◽

2019 ◽

Vol 33 (6) ◽

pp. 1031-1043

Author(s):

Ruan Yao ◽

Xuejuan Ren

Keyword(s):

Interannual Variability ◽

Yangtze River ◽

Heavy Rainfall ◽

Yangtze River Valley ◽

River Valley ◽

The Yangtze River ◽

Rainfall Events ◽

Persistent Heavy Rainfall ◽

Heavy Rainfall Events

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Two Distinct Types of 10-30-day Persistent Heavy Rainfall Events over the Yangtze River Valley

Journal of Climate ◽

10.1175/jcli-d-20-0741.1 ◽

2021 ◽

pp. 1-44

Author(s):

Yifeng Cheng ◽

Lu Wang ◽

Tim Li

Keyword(s):

Yangtze River ◽

Heavy Rainfall ◽

Yangtze River Valley ◽

The Yangtze River ◽

Rainfall Events ◽

Anticyclonic Circulation ◽

Persistent Heavy Rainfall ◽

Circulation Anomalies ◽

Upper Level ◽

Heavy Rainfall Events

AbstractLarge-scale circulation anomalies associated with 10-30-day filtered persistent heavy rainfall events (PHREs) over the middle and lower reaches of the Yangtze River Valley (MLYV) in boreal summer for the period of 1961-2017 were investigated. Two distinct types of PHREs were identified based on configurations of anomalies in western Pacific subtropical high (WPSH) and South Asian High (SAH) during the peak wet phase. One type named as PSAH is characterized by eastward extension of the SAH while the other named as NSAH is featured by westward retreat of the SAH, and they both exhibit westward extension of the WPSH. Both types of PHREs are dominated by Mei-yu frontal systems. The lower-level circulation anomalies play a crucial role in initiating rainfall but through different processes. Prior to rainfall occurrence, a strong anticyclonic circulation anomaly is over the western North Pacific (WNP) for the PSAH events and the related southwesterly wind anomaly prevails over the south-eastern China, which advects moisture into the MLYV, moistens the boundary layer, and induces atmospheric convective instability. For the NSAH events, the WNP anticyclonic circulation is weak while a strong northerly wind is observed north of the MLYV. It brings cold air mass southward, favoring initiating frontal rainfall over the MLYV. The formation of upper-level circulation anomalies over the MLYV is primarily due to the shift of anomalous circulations from mid-high latitudes. After the rainfall generation, the precipitation would influence the lower- and upper-level circulation anomalies.

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