Accumulation Gradient Altitude
Fit an observed accumulation/altitude gradient and predict only within the measured altitude range; extrapolated precipitation climatology is not invented.
Description
Accumulation may vary systematically with altitude.
Accumulation may vary systematically with altitude. An observed regression can summarize that gradient without extrapolating beyond sampled elevations.1
Fit an observed accumulation/altitude gradient and predict only within the measured altitude range; extrapolated precipitation climatology is not invented.
When to use Accumulation Gradient Altitude
Use this for the following task: Fit an observed accumulation/altitude gradient and predict only within the measured altitude range; extrapolated precipitation climatology is not invented.
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 Gradient Altitude 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 elevationsM, accumulationsMwe, queryElevationM using the field table, then run the tool.
- Read gradientMwePer100Meters, fittedAccumulationAtQueryMwe, fitRSquared. 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 |
|---|---|---|---|
| elevationsM | Elevations m | list of number; each entry: number | Required |
| accumulationsMwe | Accumulations mwe | list of number; each entry: number | Required |
| queryElevationM | Query elevation m | number | Required |
Fit aligned elevations and nonnegative accumulation measurements by least squares. Require query elevation within the observed range and return R squared with the predicted value.2
gradient per 100m = 100 regressionSlope; query accumulation = intercept + slope queryElevation This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.
| Output field | Meaning | Value type |
|---|---|---|
| gradientMwePer100Meters | Gradient mwe per100 meters | number |
| fittedAccumulationAtQueryMwe | Fitted accumulation at query mwe | number |
| fitRSquared | Fit r squared | number |
{
"input": {
"elevationsM": [
1000,
1500,
2000
],
"accumulationsMwe": [
1,
2,
3
],
"queryElevationM": 1750
},
"output": {
"gradientMwePer100Meters": 0.2,
"fittedAccumulationAtQueryMwe": 2.5,
"fitRSquared": 1
}
}Limitations and assumptions
The fit does not establish precipitation climatology or prevent a negative fitted value from an imperfect linear model.
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 Accumulation Area Ratio AAR for this operation: Estimate AAR above a supplied ELA with area uniform within each elevation band; nonuniform hypsometry and transient snowline differences are external.
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.
- 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.