Fall Turnover Density Inversion Trigger

Screen resolved down-column density inversions against caller measurement tolerance; inversion is a mixing trigger screen, not proof of complete fall turnover.

Description

Density decreasing with depth creates an inversion that can promote mixing.

Density decreasing with depth creates an inversion that can promote mixing. A caller tolerance distinguishes a resolved inversion from small measured differences.^[1]

The tool returns densityDifferencesDownwardKgPerM3, unstableIntervalFlags, hasResolvedDensityInversion. The computation uses supplied observations and parameters rather than acquiring measurements.

When to use Fall Turnover Density Inversion Trigger

Use this for the following task: Screen resolved down-column density inversions against caller measurement tolerance; inversion is a mixing trigger screen, not proof of complete fall turnover. Prepare observations and calibration parameters on the same unit and reporting basis.

How to use Fall Turnover Density Inversion Trigger and understand its results

Prepare the measured quantities and supplied model parameters. Match the units and align paired lists before calculating.
Enter depthsM, densitiesKgPerM3, inversionToleranceKgPerM3 according to the field table, then run the tool.
Read densityDifferencesDownwardKgPerM3, unstableIntervalFlags, hasResolvedDensityInversion. Use the calculation below to interpret the selected mean or the model’s signs, units and comparison flags.
Review the supplied assumptions and calibration before comparing or reporting the result.

Input field	Meaning	Value type and bounds	Requirement
depthsM	Depths m	list of number	Required
densitiesKgPerM3	Densities kg per m3	list of number	Required
inversionToleranceKgPerM3	Inversion tolerance kg per m3	number	Required

Supply aligned positive densities and increasing nonnegative depths with a nonnegative tolerance. Return differences, 1/0 interval flags and whether any interval is flagged.

difference[i]=density[i+1]−density[i]; unstable flag=1 when difference<−tolerance

The symbols and boundary conditions refer to the supplied fields and the implementation described above.

Output field	Meaning	Value type
densityDifferencesDownwardKgPerM3	Density differences downward kg per m3	list of number
unstableIntervalFlags	Unstable interval flags	list of number
hasResolvedDensityInversion	Has resolved density inversion	boolean

json

{
  "input": {
    "depthsM": [
      0,
      1,
      2
    ],
    "densitiesKgPerM3": [
      1002,
      1000,
      1001
    ],
    "inversionToleranceKgPerM3": 0.1
  },
  "output": {
    "densityDifferencesDownwardKgPerM3": [
      -2,
      1
    ],
    "unstableIntervalFlags": [
      1,
      0
    ],
    "hasResolvedDensityInversion": true
  }
}

Limitations and assumptions

Equality with the tolerance does not trigger a flag. A resolved inversion is a mixing screen rather than proof of complete autumn turnover.

Numerical inputs must be finite. Input-shape and calculation checks do not establish measurement quality or the validity of a supplied calibration.

Alternative or Complementary methods

Choose Density Gradient Stratification Strength when you need its operation: Compute signed N² from observed density gradients with depth positive down; negative values remain instability indicators rather than an invented real Brunt–Väisälä frequency. Choose Freshwater Density From Temperature for the complementary operation: Evaluate the standard empirical pure-freshwater density approximation near atmospheric pressure for 0–40°C; excludes salinity, compression and dissolved-solids effects.

Background reference: Lake Physics Tools: rLakeAnalyzer reference manual.

References

Lake Physics Tools: rLakeAnalyzer reference manual — Winslow, Read and colleagues; GLEON

Similar or alternative tools

Density Gradient Stratification Strength
Compute signed N² from observed density gradients with depth positive down; negative values remain instability indicators rather than an invented real Brunt–Väisälä frequency.
Freshwater Density From Temperature
Evaluate the standard empirical pure-freshwater density approximation near atmospheric pressure for 0–40°C; excludes salinity, compression and dissolved-solids effects.