Ono et al. (2025) Estimating Maximum Precipitation for an Extreme Rainfall Event in Japan Using Lower-Level Shifts of Atmospheric Initial and Boundary Conditions

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Identification

• Journal: Journal of Hydrometeorology
• Year: 2025
• Date: 2025-11-07
• Authors: Akiyuki Ono, Kosei Yamaguchi
• DOI: 10.1175/jhm-d-25-0118.1

Research Groups

Not explicitly stated in the provided text.

Short Summary

This study investigates the sensitivity of maximum precipitation (MP) estimates to different atmospheric initial and boundary condition (AIBC) shifting methods using a high-resolution weather model. It finds that a novel lower-level shift (LLS) method, focusing on lower-tropospheric moisture, significantly increases estimated 6-hour precipitation by 65% compared to traditional all-layer shifts (ALS), which showed only slight increases.

Objective

• To investigate the sensitivity of maximum precipitation (MP) estimates over the upstream regions of the Katsuragawa and Kamogawa River basins to different atmospheric initial and boundary condition (AIBC) shifting methods.

Study Configuration

• Spatial Scale: Regional scale, specifically the upstream regions of the Katsuragawa and Kamogawa River basins (localized, less than 100 km).
• Temporal Scale: 6 hours.

Methodology and Data

• Models used: Cloud-Resolving Storm Simulator (CReSS), a numerical weather prediction (NWP) model.
• Data sources: Numerical simulations based on shifted atmospheric initial and boundary conditions (AIBCs). Two shifting approaches were evaluated: all-layer shifts (ALS) and lower-level shifts (LLS, below 700 hPa).

Main Results

• All-layer shifts (ALS) experiments produced only slight increases in precipitation compared to the control simulation and showed a decreasing trend with greater shifts, attributed to northward displacement of midlevel dry air.
• Lower-level shifts (LLS) simulations with a 0.6° northward shift yielded a 65% increase in 6-hour precipitation over the target basins.
• LLS runs effectively captured rapid rainfall intensification driven by enhanced moisture transport and convergence over mountainous terrain.
• The study concludes that ALS does not consistently provide effective MP estimates for localized extreme rainfall events, and the lower-level atmospheric environment significantly influences precipitation intensity and spatial distribution.

Contributions

• Introduces and validates a novel lower-level atmospheric shifting (LLS) method for estimating maximum precipitation, demonstrating its superiority over traditional all-layer shifts for localized extreme rainfall events.
• Highlights the critical role of lower-tropospheric moisture transport and convergence in driving intense, localized precipitation.
• Provides a valuable approach for identifying potential flood risks from localized heavy rain, thereby improving disaster preparedness.

Funding

Not explicitly stated in the provided text.

Citation

@article{Ono2025Estimating,
  author = {Ono, Akiyuki and Yamaguchi, Kosei},
  title = {Estimating Maximum Precipitation for an Extreme Rainfall Event in Japan Using Lower-Level Shifts of Atmospheric Initial and Boundary Conditions},
  journal = {Journal of Hydrometeorology},
  year = {2025},
  doi = {10.1175/jhm-d-25-0118.1},
  url = {https://doi.org/10.1175/jhm-d-25-0118.1}
}