CAPE Convective Available Potential Energy

Integrate positive portions of caller precomputed virtual parcel/environment buoyancy in observed height window, resolving each linear zero crossing; no hidden parcel lift, full sounding CAPE outside coverage or storm safety.

Description

CAPE measures positive buoyancy available to a parcel within a declared height layer.

CAPE measures positive buoyancy available to a parcel within a declared height layer. Supplied virtual temperatures account for the temperature-density relation without hiding a parcel-lift calculation.^[1]

When to use CAPE Convective Available Potential Energy

Use this tool to integrate positive portions of caller precomputed virtual parcel/environment buoyancy in observed height window, resolving each linear zero crossing; no hidden parcel lift, full sounding CAPE outside coverage or storm safety.

Prepare the observed sounding, cloud records or forecast verification data. Check pressure and height coordinates, wind conventions and the stated units.

How to use CAPE Convective Available Potential Energy and understand its results

Prepare the observed sounding, cloud records or forecast verification data. Check pressure and height coordinates, wind conventions and the stated units.
Enter heightsM, parcelVirtualTemperaturesK, environmentVirtualTemperaturesK, gravityMPerSecondSquared, integrationBottomM, integrationTopM using the field table and calculation rules, then run the tool.
Read positiveBuoyancyCapeJPerKg, integratedBuoyancyMPerSecond2. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
heightsM	Heights m	list of number	Required
parcelVirtualTemperaturesK	Parcel virtual temperatures k	list of number	Required
environmentVirtualTemperaturesK	Environment virtual temperatures k	list of number	Required
gravityMPerSecondSquared	Gravity m per second squared	number	Required
integrationBottomM	Integration bottom m	number	Required
integrationTopM	Integration top m	number	Required

Use positive virtual Kelvin temperatures and gravity with increasing heights and in-coverage bottom/top bounds. Interpolate boundary buoyancies and integrate positive portions of linear segments, splitting zero crossings. Return J/kg and buoyancies at the clipped profile nodes.

CAPE = ∫max[g(Tvirtual parcel−Tvirtual environment)/Tvirtual environment,0] dz

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
positiveBuoyancyCapeJPerKg	Positive buoyancy cape j per kg	number
integratedBuoyancyMPerSecond2	Integrated buoyancy m per second2	list of number

json

{
  "input": {
    "heightsM": [
      0,
      1000,
      2000
    ],
    "parcelVirtualTemperaturesK": [
      300,
      330,
      300
    ],
    "environmentVirtualTemperaturesK": [
      300,
      300,
      300
    ],
    "gravityMPerSecondSquared": 10,
    "integrationBottomM": 0,
    "integrationTopM": 2000
  },
  "output": {
    "positiveBuoyancyCapeJPerKg": 1000,
    "integratedBuoyancyMPerSecond2": [
      0,
      1,
      0
    ]
  }
}

Limitations and assumptions

The caller provides parcel temperatures and the layer. Complete-sounding CAPE outside observations is not inferred.

Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use CIN Convective Inhibition: Integrate only negative caller parcel virtual-buoyancy segments in bounded observed window, retaining signed CIN and magnitude; boundary choices/parcel lift are caller declared, not inferred complete sounding inhibition. For a complementary task, use LFC Level Free Convection: Find first strict-positive buoyancy transition at/above caller LCL in supplied linear sounding, with left-censoring or explicit no-observed-LFC sentinel; touches without positive buoyancy are not free convection.

References

CAPE Convective Available Potential Energy — tool.io

Similar or alternative tools

CIN Convective Inhibition
Integrate only negative caller parcel virtual-buoyancy segments in bounded observed window, retaining signed CIN and magnitude; boundary choices/parcel lift are caller declared, not inferred complete sounding inhibition.
LFC Level Free Convection
Find first strict-positive buoyancy transition at/above caller LCL in supplied linear sounding, with left-censoring or explicit no-observed-LFC sentinel; touches without positive buoyancy are not free convection.