Density Current Plunge Depth

Interpolate neutral-buoyancy depth for an inflow in a strictly stable measured density profile; unbracketed underflow/overflow remains censored, and entrainment, slope and momentum are not modeled.

Description

An inflow can reach neutral buoyancy where its density matches the ambient column.

An inflow can reach neutral buoyancy where its density matches the ambient column. A strictly increasing measured density profile provides a single bracketed crossing.^[1]

The tool returns neutralBuoyancyPlungeDepthM. The computation uses supplied observations and parameters rather than acquiring measurements.

When to use Density Current Plunge Depth

Use this for the following task: Interpolate neutral-buoyancy depth for an inflow in a strictly stable measured density profile; unbracketed underflow/overflow remains censored, and entrainment, slope and momentum are not modeled. Prepare observations and calibration parameters on the same unit and reporting basis.

How to use Density Current Plunge Depth and understand its results

Prepare the measured quantities and supplied model parameters. Match the units and align paired lists before calculating.
Enter depthsM, ambientDensitiesKgPerM3, inflowDensityKgPerM3 according to the field table, then run the tool.
Read neutralBuoyancyPlungeDepthM. 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
ambientDensitiesKgPerM3	Ambient densities kg per m3	list of number	Required
inflowDensityKgPerM3	Inflow density kg per m3	number	Required

Provide increasing nonnegative depths and aligned positive, strictly increasing ambient densities, with positive inflow density. Return the unique sampled or between-sample match.

plunge depth = linearly interpolated depth where ambientDensity equals inflowDensity

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

Output field	Meaning	Value type
neutralBuoyancyPlungeDepthM	Neutral buoyancy plunge depth m	number

json

{
  "input": {
    "depthsM": [
      0,
      10,
      20
    ],
    "ambientDensitiesKgPerM3": [
      1000,
      1001,
      1002
    ],
    "inflowDensityKgPerM3": 1001.5
  },
  "output": {
    "neutralBuoyancyPlungeDepthM": 15
  }
}

Limitations and assumptions

Unbracketed overflow or underflow conditions are rejected rather than extrapolated. Momentum, entrainment, bottom slope and subsequent density-current travel are not modeled.

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 Thermocline Depth Max Gradient for the complementary operation: Identify a unique maximum absolute interval temperature gradient, reporting interval center rather than claiming sub-sample thermocline precision.

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.
Thermocline Depth Max Gradient
Identify a unique maximum absolute interval temperature gradient, reporting interval center rather than claiming sub-sample thermocline precision.