Mean Relative Humidity (2020–2024)

Overview

This dataset represents modeled global mean annual relative humidity developed to support ISO 9223 atmospheric corrosivity modeling for the period 2020–2024.

Relative humidity is one of the most important environmental variables influencing:

• Atmospheric corrosion
• Time of Wetness (TOW)
• Electrolyte formation
• Chloride persistence
• Sulfate deposition chemistry
• Atmospheric conductivity

The raster represents estimated long-term mean atmospheric relative humidity conditions at approximately 1 km spatial resolution.

Units:

• Relative Humidity (%)
• Range: 0–100%

Background

Relative humidity is a core environmental variable within the ISO 9223 atmospheric corrosivity framework and strongly influences moisture-related corrosion processes.

Relative humidity directly affects:

• Electrolyte formation on metal surfaces
• Time of Wetness persistence
• Atmospheric conductivity
• Chloride retention
• Sulfate reaction chemistry
• Corrosion cell formation and persistence

Higher humidity environments generally promote increased atmospheric corrosion activity, particularly when combined with chloride deposition, sulfate deposition, and elevated temperatures.

This dataset was developed to provide global humidity estimates suitable for corrosion engineering, environmental modeling, and GIS-based exposure assessment.

Modeling Methodology

The humidity framework integrates atmospheric observations, climate reanalysis products, offshore measurements, and spatial interpolation methods.

Primary humidity inputs include:

• Surface meteorological observations
• Offshore buoy observations
• Climate reanalysis datasets
• Satellite-derived atmospheric moisture products

The modeling framework incorporates:

Atmospheric Observations

• NOAA Integrated Surface Database (ISD)
• Government of Canada climate stations
• National Data Buoy Center (NDBC) observations

Climate Reanalysis

• NASA MERRA-2 atmospheric products
• Regional climate datasets
• Long-term climatological averages

Spatial Modeling

• Ordinary Kriging
• Empirical Bayesian Kriging
• Spatial interpolation methods
• Coastal correction techniques

Environmental Integration

• Coastal influences
• Regional climate gradients
• Atmospheric moisture consistency checks
• Long-term climatological averaging

The resulting framework was designed to improve representation of ambient atmospheric humidity behavior across coastal, inland, tropical, arid, and remote environments.

Interpretation Guidelines

Relative humidity is one of the strongest predictors of atmospheric corrosion potential, particularly when combined with elevated chloride deposition and persistent surface wetness.

Spatial Resolution

Data Sources

Primary environmental inputs include:

• NOAA Integrated Surface Database (ISD)
• NASA MERRA-2 Atmospheric Reanalysis
• Government of Canada Climate Database
• National Data Buoy Center (NDBC)
• Supplemental atmospheric and climate datasets

Derived environmental layers include:

• Temperature
• Chloride Deposition
• Sulfate Deposition
• Time of Wetness (TOW)
• Atmospheric Corrosion Layers

Intended Applications

This dataset may be used for:

• Atmospheric corrosion assessment
• ISO 9223 modeling
• Time of Wetness estimation
• Climate exposure analysis
• Environmental severity assessment
• Corrosion engineering
• GIS visualization
• Environmental modeling
• Enterprise API workflows

Related Datasets

Corrosion Layers

• ISO 9223 Steel Corrosion Rate
• ISO 9223 Zinc Corrosion Rate
• ISO 9223 Aluminum Corrosion Rate
• ISO 9223 Copper Corrosion Rate

Supporting Atmospheric Layers

• Mean Chloride Deposition
• Mean Sulfate Deposition
• Mean Annual Temperature
• Time of Wetness (TOW)

Supporting Coastal & Terrain Layers

• Distance to Coast
• Bathymetry 2024 – Terrain Elevation
• WindRIX Terrain–Wind Exposure Index
• Wind Resultant Direction (0–360°)
• Wind Speed

Attribution

Joseph Mazzella
AtmosphericIQ LLC
Engineering Director, Inc.

Dataset Citation

Mazzella, J. (2026). Mean Relative Humidity Raster (2020–2024). AtmosphericIQ LLC / Engineering Director, Inc.

Supporting Dataset Citations

NOAA ISD

NOAA National Centers for Environmental Information (NCEI). Integrated Surface Database (ISD).
https://www.ncei.noaa.gov/products/land-based-station/integrated-surface-database

NASA MERRA-2

NASA Global Modeling and Assimilation Office (GMAO). MERRA-2 Atmospheric Reanalysis Dataset.
https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/

Government of Canada Climate Data

Environment and Climate Change Canada. Historical Climate Data.
https://climate.weather.gc.ca/

National Data Buoy Center

National Oceanic and Atmospheric Administration (NOAA). National Data Buoy Center (NDBC).
https://www.ndbc.noaa.gov/

ISO 9223 Standard

ISO 9223:2012. Corrosion of metals and alloys — Corrosivity of atmospheres — Classification, determination and estimation.
https://www.iso.org/standard/53499.html

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