DCAPE Downdraft CAPE Calculator
Integrate positive downward buoyancy g(TvEnv−TvDescended)/TvEnv over observed height window, resolving linear zero crossings; caller independently descends saturated downdraft parcel, not upward CAPE or full sounding. Caller independently establishes matching units, evidence, method edition and applicability; output is not compliance, diagnosis, work-safety approval, geological identity or validated hazard prediction.
Description
Downdraft CAPE represents integrated favorable downdraft buoyancy along an independently supplied parcel profile.
Downdraft CAPE represents integrated favorable downdraft buoyancy along an independently supplied parcel profile.1
Virtual temperatures and height coordinates must describe the same column and descent calculation.
When to use DCAPE Downdraft CAPE Calculator
Use this tool to calculate or review the supplied observations under the stated rules. Establish the observation method, units, averaging period and applicable reference or calibration.
How to use DCAPE Downdraft CAPE Calculator and understand its results
- Establish the observation method, units, averaging period and applicable reference or calibration.
- Enter observedHeightsM, environmentVirtualTemperatureK, independentlyDescendedParcelVirtualTemperatureK, gravityMS2, using the field meanings and rules below, then run the tool.
- Read observedDcapeJKg, using the output meanings and calculation rules below.
- Correct any reported input issue and run again. Before using a successful result, check the stated units, signs, reference scope and observation coverage.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| observedHeightsM | Observed heights m | list of number | Required |
| environmentVirtualTemperatureK | Environment virtual temperature k | list of number | Required |
| independentlyDescendedParcelVirtualTemperatureK | Independently descended parcel virtual temperature k | list of number | Required |
| gravityMS2 | Gravity m s2 | number | Required |
Require at least two aligned strictly increasing finite heights, positive environmental and descended-parcel virtual temperatures and positive gravity. Compute g×(environmentTv−parcelTv)/environmentTv at each sample. Integrate only the positive part of each linearly interpolated buoyancy segment: full positive trapezoids, zero for wholly nonpositive segments, and an exactly located triangular portion at a sign crossing.
B_i=g(Tv_env,i−Tv_parcel,i)/Tv_env,i; DCAPE=∫ sampled height range max(0,linearInterpolate(B)) dz Use the matching field units and the exact boundary, ordering and reference rules above.
| Output field | Meaning | Value type |
|---|---|---|
| observedDcapeJKg | Observed dcape j kg | number |
{
"input": {
"observedHeightsM": [
0,
1,
2
],
"environmentVirtualTemperatureK": [
300,
300,
300
],
"independentlyDescendedParcelVirtualTemperatureK": [
290,
300,
310
],
"gravityMS2": 10
},
"output": {
"observedDcapeJKg": 0.16666666666666666
}
}Limitations and assumptions
The descent trajectory and virtual-temperature corrections are supplied, not calculated. Negative height coordinates are accepted when strictly increasing. The sampled column, interpolation and parcel assumptions limit interpretation.
Missing required fields, unknown fields, wrong types and violated rules return input issues. Numeric values and outputs must be finite. Lists and matrices must be dense, without missing cells. Numeric lists allow at most 10000 entries; ordinary string lists allow at most 128 strings of 128 UTF-16 units each; numeric matrices allow at most 128 rows and 128 columns, subject to narrower requirements above.
Alternative or Complementary methods
For a related step, use Significant Tornado Parameter STP Calculator: The significant tornado parameter combines instability, rotation, shear, cloud-base height and inhibition into a dimensionless environmental index. For a complementary comparison, use Microburst vs Macroburst Classifier: Microburst and macroburst labels concern the spatial extent of a downburst.
References
-
DCAPE Downdraft CAPE Calculator — tool.io
Similar or alternative tools
- Significant Tornado Parameter STP Calculator
The significant tornado parameter combines instability, rotation, shear, cloud-base height and inhibition into a dimensionless environmental index.
- Microburst vs Macroburst Classifier
Microburst and macroburst labels concern the spatial extent of a downburst.