Blanco et al. (2026) On two definitions for precipitation intensity: differences, artifacts and ambiguities

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

Identification

• Journal: Journal of Hydrometeorology
• Year: 2026
• Date: 2026-02-04
• Authors: Joaquin Blanco, Si Cheng, Lisa V. Alexander
• DOI: 10.1175/jhm-d-25-0144.1

Research Groups

Not available in the provided abstract.

Short Summary

This study assesses the differences between two widely used precipitation intensity definitions (I and Iwet) in arid and semi-arid regions using global precipitation data. It finds that I consistently inflates values compared to Iwet, with differences exceeding 100% in arid regions, and advocates for the use of I_wet for more accurate quantification.

Objective

• To assess the differences arising from two widely used precipitation intensity definitions (I and I_wet) and their implications for environmental and infrastructural impacts in arid and semi-arid regions.

Study Configuration

• Spatial Scale: Global, gridded precipitation, with a focus on arid and semi-arid regions.
• Temporal Scale: Daily precipitation rates, averaged over entire analysis periods, and evaluated over two adjacent 20-year periods.

Methodology and Data

• Models used: Comparison of two precipitation intensity definitions:
  • I: Average daily precipitation rate over the entire analysis period (P) divided by the frequency of occurrence of wet days (Fwet), where wet days are defined as accumulations of at least 1 mm.
  • Iwet: Precipitation rate averaged over wet days only, where wet days are defined as accumulations of at least 1 mm.
• Data sources: Global, gridded precipitation from reanalyses, satellite-derived products, and gauge-derived products.

Main Results

• The precipitation intensity metric I is consistently greater than Iwet (I > Iwet).
• The relative difference between I and Iwet scales inversely with the frequency of wet days (Fwet).
• Over semi-arid regions, the I metric typically inflates values by at least 10% compared to I_wet.
• Over arid regions, the difference between I and I_wet can exceed 100%.
• Singularities were found where I may become larger than the climatological extreme, which is not observed for I_wet.
• The sign of the relative change in intensity from two adjacent 20-year periods can differ depending on whether I or I_wet is used.
• For very arid regions, defining wet days as rates greater than 1 mm may account for smaller precipitation accumulations than "dry" days (less than 1 mm).
• Artifacts can be circumvented by adopting a wet day threshold of 0.1 mm.
• The study advocates for the use of the I_wet metric and emphasizes the need for clear and unambiguous nomenclatures.

Contributions

• Quantifies and highlights significant differences between two common precipitation intensity definitions (I and I_wet), particularly in arid and semi-arid regions.
• Demonstrates that the I metric can substantially inflate precipitation intensity values and even exceed climatological extremes.
• Reveals that the choice of definition can alter the perceived sign of change in precipitation intensity over time.
• Identifies a practical issue with the 1 mm wet day threshold in very arid regions and proposes a solution (0.1 mm threshold).
• Provides a strong recommendation for the use of the I_wet metric and for clearer scientific nomenclature in precipitation studies.

Funding

Not available in the provided abstract.

Citation

@article{Blanco2026two,
  author = {Blanco, Joaquin and Cheng, Si and Alexander, Lisa V.},
  title = {On two definitions for precipitation intensity: differences, artifacts and ambiguities},
  journal = {Journal of Hydrometeorology},
  year = {2026},
  doi = {10.1175/jhm-d-25-0144.1},
  url = {https://doi.org/10.1175/jhm-d-25-0144.1}
}