Jeong et al. (2026) Atmospheric circulation and moisture budget drivers of dominant modes of winter extreme precipitation variability over North America

Identification

• Journal: Climate Dynamics
• Year: 2026
• Date: 2026-04-01
• Authors: Dae Il Jeong, Bin Yu, Alex J. Cannon
• DOI: 10.1007/s00382-026-08125-z

Research Groups

• Climate Research Division, Environment and Climate Change Canada, Toronto, ON, Canada
• Climate Research Division, Environment and Change Canada, Victoria, BC, Canada

Short Summary

This study identifies three dominant modes of winter extreme precipitation variability (monthly maximum consecutive 5-day precipitation, Rx5day) across North America, explaining 30.7% of total variance, and attributes them to large-scale atmospheric circulation and lower-tropospheric wind-driven moisture transport.

Objective

• To identify the dominant modes of monthly maximum consecutive 5-day precipitation (Rx5day) variability across North America during the extended winter season (November–March) from 1961 to 2023.
• To investigate the large-scale dynamical, thermodynamical, and atmospheric moisture budget drivers influencing these dominant modes.

Study Configuration

• Spatial Scale: North America (25°–75°N, 140°–52°W), with analysis of large-scale dynamic and thermodynamic processes over the Northern Hemisphere.
• Temporal Scale: Extended winter months (November–March) from 1961 to 2023, analyzing monthly maximum consecutive 5-day precipitation (Rx5day).

Methodology and Data

• Models used: Not applicable (reanalysis datasets used).
• Data sources:
  • European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis version 5 (ERA5): 0.25° horizontal grid spacing.
  • Japanese 55-year Reanalysis (JRA-55): 1.25° horizontal grid spacing.
  • Variables: Tropospheric geopotential height, U- and V-wind components, specific humidity (from 1000 hPa to 100 hPa), total precipitation, total column vertically integrated water vapor (TCWV), sea surface temperature (SST), and outgoing longwave radiation (OLR).
  • Methodology: Data interpolated to a common 2.5° × 2.5° grid. Common Empirical Orthogonal Function (EOF) analysis, linear regression, and atmospheric moisture budget analysis (decomposing total moisture flux divergence into mean and transient components).

Main Results

• Three dominant modes of monthly Rx5day variability were identified, collectively accounting for 30.7% of the total variance over North America, with distinct positive and negative anomaly centers across western and eastern regions.
• These modes are primarily driven by large-scale atmospheric circulation anomalies, characterized by wave trains extending from the North Pacific across North America to the North Atlantic, and atmospheric moisture anomalies.
• Wind-driven moisture transport, concentrated in the lower troposphere (surface to approximately 500 hPa), is a key driver, with anomalous westerly and southerly flows bringing moisture from the Pacific to western North America and from the Gulf of Mexico to southeastern North America.
• Upward motion and deep tropospheric moisture columns enhance extreme precipitation in these regions.
• Moisture budget analysis revealed that moisture flux convergence is the principal mechanism supplying water vapor for these extreme events, with local evaporation playing a minor role.
• Specifically, the convergence of mean moisture by transient winds ( (-\nabla\cdot\overline{\text{q}}{\mathbf{v}}^{{\prime}}) ) emerged as the primary driver of extreme precipitation variability, with its contribution often exceeding that of total moisture flux convergence.
• Moisture budget components at 850 hPa closely reflect their vertically integrated counterparts, underscoring the pivotal role of lower-tropospheric dynamics in moisture transport and convergence processes.
• Linkages between the dominant Rx5day modes and Northern Hemisphere teleconnection indices were generally weak, with linear correlation coefficients typically less than 0.3 in magnitude.
• The second and third modes showed consistency with composite precipitation and geopotential height anomaly patterns during extreme El Niño and La Niña events, respectively, suggesting teleconnections with ENSO-like tropical SST anomalies.

Contributions

• Provides the first comprehensive, North America-wide climatological analysis of dominant modes of extended winter extreme precipitation variability (Rx5day), moving beyond previous studies focused on specific subregions or individual mechanisms.
• Quantifies the relative importance of large-scale dynamical, thermodynamical, and specific moisture budget components in driving these continent-wide extreme precipitation modes.
• Identifies the convergence of mean moisture by transient winds as a key modulator of moisture convergence for extreme precipitation variability, extending previous regional findings to a broader climatological perspective.
• Highlights that Rx5day variability captures distinct, episodic extreme-event-driven aspects of hydroclimatic variability, differentiating it from broader monthly precipitation accumulations.

Funding

Open access funding provided by Environment & Climate Change Canada library.

Citation

@article{Jeong2026Atmospheric,
  author = {Jeong, Dae Il and Yu, Bin and Cannon, Alex J.},
  title = {Atmospheric circulation and moisture budget drivers of dominant modes of winter extreme precipitation variability over North America},
  journal = {Climate Dynamics},
  year = {2026},
  doi = {10.1007/s00382-026-08125-z},
  url = {https://doi.org/10.1007/s00382-026-08125-z}
}