Accumulation Area Ratio AAR
Estimate AAR above a supplied ELA with area uniform within each elevation band; nonuniform hypsometry and transient snowline differences are external.
Description
Accumulation-area ratio is the glacier area above an equilibrium line divided by total area.
Accumulation-area ratio is the glacier area above an equilibrium line divided by total area. Elevation-band geometry affects the fraction that lies above the line.1
Estimate AAR above a supplied ELA with area uniform within each elevation band; nonuniform hypsometry and transient snowline differences are external.
When to use Accumulation Area Ratio AAR
Use this for the following task: Estimate AAR above a supplied ELA with area uniform within each elevation band; nonuniform hypsometry and transient snowline differences are external.
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 Accumulation Area Ratio AAR 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 bandLowerElevationsM, bandUpperElevationsM, bandAreasM2, equilibriumLineElevationM using the field table, then run the tool.
- Read accumulationAreaM2, totalGlacierAreaM2, accumulationAreaRatio. 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 |
|---|---|---|---|
| bandLowerElevationsM | Band lower elevations m | list of number; each entry: number | Required |
| bandUpperElevationsM | Band upper elevations m | list of number; each entry: number | Required |
| bandAreasM2 | Band areas m2 | list of number; each entry: number | Required |
| equilibriumLineElevationM | Equilibrium line elevation m | number | Required |
Supply ordered nonoverlapping positive-height bands with positive areas. Allocate partial bands uniformly with elevation and sum area above the supplied ELA.2
Aabove = Σ bandArea clamp((upper−max(lower,ELA))/(upper−lower),0,1); AAR = Aabove/Atotal This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.
| Output field | Meaning | Value type |
|---|---|---|
| accumulationAreaM2 | Accumulation area m2 | number |
| totalGlacierAreaM2 | Total glacier area m2 | number |
| accumulationAreaRatio | Accumulation area ratio | number |
{
"input": {
"bandLowerElevationsM": [
100,
200
],
"bandUpperElevationsM": [
200,
300
],
"bandAreasM2": [
100,
200
],
"equilibriumLineElevationM": 250
},
"output": {
"accumulationAreaM2": 100,
"totalGlacierAreaM2": 300,
"accumulationAreaRatio": 0.3333333333333333
}
}Limitations and assumptions
Uniform area within each band is an assumption. A transient snowline need not equal the equilibrium line.
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 Equilibrium Line Altitude ELA for this operation: Find the unique observed zero of a piecewise-linear altitude/net-balance profile; missing and multiple equilibrium lines are not extrapolated or arbitrarily selected. For a complementary task, use Annual Mass Balance for this operation: Area-weight annual accumulation minus ablation over matched nonoverlapping glacier zones; quantities are water equivalent and negative balances are preserved.
Further background: Glacier accumulation, ablation and mass balance.
References
Similar or alternative tools
- Equilibrium Line Altitude ELA
Find the unique observed zero of a piecewise-linear altitude/net-balance profile; missing and multiple equilibrium lines are not extrapolated or arbitrarily selected.
- Annual Mass Balance
Area-weight annual accumulation minus ablation over matched nonoverlapping glacier zones; quantities are water equivalent and negative balances are preserved.