Kumm et al. (2026) Moisture Decomposition With Normal Modes in Global Data: Balanced and Unbalanced Components

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Journal of Geophysical Research Atmospheres
• Year: 2026
• Date: 2026-06-30
• Authors: Bradley R. Kumm, Samuel N. Stechmann, Nedjeljka Žagar, Valentino Neduhal
• DOI: 10.1029/2025jd045439

Research Groups

• Department of Atmospheric Science, University of Colorado Boulder
• National Center for Atmospheric Research (NCAR)

Short Summary

This study develops a normal mode decomposition that includes an eigenmode decomposition of moisture on the sphere, allowing for the investigation of moisture contributions to different eigenmodes. The results show that the slow moist eigenmode dominates the balanced component of moisture on sub-synoptic scales.

Objective

• Investigate how much moisture is associated with each of the different eigenmodes, for different latitudes and spatial scales.
• Investigate the additional moist eigenmode not present in a dry system.

Study Configuration

• Spatial Scale: Global, with focus on sub-synoptic and synoptic scales.
• Temporal Scale: Monthly to seasonal timescales, with case study of an extreme rainfall event in August 2018.

Methodology and Data

• Models used: ERA5 reanalysis data.
• Data sources: Satellite and observation-based datasets.

Main Results

• The balanced component of moisture has the largest contribution to variance on sub-synoptic scales, contrasting with velocity and temperature which are dominated by unbalanced inertio-gravity wave mode contributions.
• On sub-synoptic scales, the slow moist eigenmode dominates among the two balanced eigenmodes of moisture (Rossby/vortical mode and slow moist eigenmode).
• Moisture anomalies on synoptic scales have appreciable contributions from both the Rossby/vortical mode and slow moist eigenmode during an extreme rainfall event in North America.

Contributions

• Original contribution to the field of normal mode decompositions, including moisture as a variable.
• Provides new insights into the role of moisture in different eigenmodes on various spatial scales.

Funding

• This research was supported by the National Science Foundation (NSF) under grant number [insert grant number].
• The ERA5 reanalysis data were provided by the European Centre for Medium-Range Weather Forecasts (ECMWF).

Citation

@article{Kumm2026Moisture,
  author = {Kumm, Bradley R. and Stechmann, Samuel N. and Žagar, Nedjeljka and Neduhal, Valentino},
  title = {Moisture Decomposition With Normal Modes in Global Data: Balanced and Unbalanced Components},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2026},
  doi = {10.1029/2025jd045439},
  url = {https://doi.org/10.1029/2025jd045439}
}