Liu et al. (2025) Dynamic processes and mechanisms of the Quasi-Biweekly Oscillation of summer precipitation in the middle and lower reaches of the Yangtze River

Identification

• Journal: Atmospheric Research
• Year: 2025
• Date: 2025-10-31
• Authors: Yihan Liu, Suxiang Yao, Yanfei Shi
• DOI: 10.1016/j.atmosres.2025.108606

Research Groups

• State Key Laboratory of Climate System Prediction and Risk Management/Key Laboratory of Meteorological Disaster, Ministry of Education/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing, China
• School of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing, China
• Liaoning Meteorological Service Center, Shenyang, China

Short Summary

This study investigates the dynamic processes and mechanisms of the Quasi-Biweekly Oscillation (QBWO) of summer precipitation in the middle and lower reaches of the Yangtze River (MLYR), revealing that low-level vorticity development, driven by vortex tube stretching and multiscale interactions, maintains the QBWO.

Objective

• To analyze the circulation patterns and dynamical mechanisms associated with the wet and dry phases of summer precipitation QBWO over the MLYR, clarifying how monsoon background circulation and synoptic-scale nonlinear processes collectively modulate this oscillation.

Study Configuration

• Spatial Scale: Middle and lower reaches of the Yangtze River (MLYR)
• Temporal Scale: Summer (June-August) precipitation from 1983 to 2022

Methodology and Data

• Models used: Vorticity budget diagnosis, Multiscale vorticity budget analysis
• Data sources: Observed precipitation, ERA5 reanalysis data

Main Results

• Summer precipitation QBWO in the MLYR is tightly coupled with low-level (850 hPa) vorticity anomalies.
• The wet phase features a low-level (850 hPa) quasi-biweekly cyclonic anomaly enhancing convergence and an upper-level (200 hPa) anticyclonic anomaly promoting divergence, while the dry phase exhibits opposite anomalies.
• Quasi-biweekly low-level vorticity development is primarily maintained by vortex tube stretching, driven by quasi-biweekly divergence acting on planetary and background vorticity, and background wind convergence acting on quasi-biweekly vorticity.
• Synoptic-scale vorticity and divergence consistently generate positive vorticity, with enhanced generation during the wet phase, reinforcing the QBWO.
• Relative vorticity advection generally inhibits vorticity maintenance, particularly due to stronger negative contributions from synoptic-scale vorticity advection in the wet phase and north-south asymmetric advection by monsoon southerly wind.

Contributions

• Clarifies the dynamic processes and mechanisms, including multiscale interactions, that modulate the QBWO of summer precipitation in the MLYR.
• Advances understanding of how monsoon background circulation and synoptic-scale nonlinear processes collectively influence intraseasonal variability.

Funding

• Not specified in the provided text.

Citation

@article{Liu2025Dynamic,
  author = {Liu, Yihan and Yao, Suxiang and Shi, Yanfei},
  title = {Dynamic processes and mechanisms of the Quasi-Biweekly Oscillation of summer precipitation in the middle and lower reaches of the Yangtze River},
  journal = {Atmospheric Research},
  year = {2025},
  doi = {10.1016/j.atmosres.2025.108606},
  url = {https://doi.org/10.1016/j.atmosres.2025.108606}
}