Firn Air Content Percentage
Integrate air volume fraction 1−rho/rho_ice through layered firn; assumes pore space is air and excludes liquid water and pressure-compressed gas.
Description
Firn’s pore space lowers its bulk density.
Firn’s pore space lowers its bulk density. Integrating the air fraction through layers gives an air-equivalent column thickness.
Integrate air volume fraction 1−rho/rho_ice through layered firn; assumes pore space is air and excludes liquid water and pressure-compressed gas.
When to use Firn Air Content Percentage
Use this for the following task: Integrate air volume fraction 1−rho/rho_ice through layered firn; assumes pore space is air and excludes liquid water and pressure-compressed gas.
Prepare the measurements and calibration parameters in the declared units. Keep vector entries aligned and choose a consistent spatial frame and time basis.
How to use Firn Air Content Percentage and understand its results
- Prepare the measurements and calibration parameters in the declared units. Keep vector entries aligned and choose a consistent spatial frame and time basis.
- Enter layerThicknessesM, layerDensitiesKgPerM3, iceDensityKgPerM3 using the field table, then run the tool.
- Read firnAirEquivalentThicknessM, columnAirVolumePercent. Interpret flags, units, ordering and placeholder values using the rules below.
- Review any reported issue or failed check, correct the supplied values when appropriate, and verify the result in its intended context.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| layerThicknessesM | Layer thicknesses m | list of number; each entry: number | Required |
| layerDensitiesKgPerM3 | Layer densities kg per m3 | list of number; each entry: number | Required |
| iceDensityKgPerM3 | Ice density kg per m3 | number | Required |
Pair positive layer thicknesses/densities and require each density no greater than ice density. Sum air-equivalent thickness and normalize by total column thickness.1
airThickness = Σ layerH(1−ρlayer/ρice); airPercent = 100 airThickness/ΣlayerH This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.
| Output field | Meaning | Value type |
|---|---|---|
| firnAirEquivalentThicknessM | Firn air equivalent thickness m | number |
| columnAirVolumePercent | Column air volume percent | number |
{
"input": {
"layerThicknessesM": [
10,
20
],
"layerDensitiesKgPerM3": [
450,
900
],
"iceDensityKgPerM3": 900
},
"output": {
"firnAirEquivalentThicknessM": 5,
"columnAirVolumePercent": 16.666666666666668
}
}Limitations and assumptions
Pores are assumed air-filled. Liquid water and pressure-compressed gas are excluded.
Constants and empirical coefficients are supplied rather than calibrated. Check units and observational applicability before interpreting the model. Malformed requests produce input errors. A successfully evaluated request can still contain false flags, empty result lists or a result outside the supplied threshold; those outcomes have the meanings stated above.
Alternative or Complementary methods
Choose Firn Density Depth Profile for this operation: Evaluate an explicitly calibrated exponential firn density-depth profile; distinct from stage-specific temperature/accumulation densification kinetics. For a complementary task, use Freeboard Flotation Requirement for this operation: Infer freely floating thickness and draft from measured freeboard with explicit firn-air correction; unsupported if grounded, flexing or under external loads.
The implementation reference documents the exact calculation, supported input shapes and returned fields.
References
-
Firn Air Content Percentage — tool.io
Similar or alternative tools
- Firn Density Depth Profile
Evaluate an explicitly calibrated exponential firn density-depth profile; distinct from stage-specific temperature/accumulation densification kinetics.
- Freeboard Flotation Requirement
Infer freely floating thickness and draft from measured freeboard with explicit firn-air correction; unsupported if grounded, flexing or under external loads.