Description
Calculate a supplied logarithmic-pressure interpolation coordinate.
Atmospheric values depend on pressure order, vertical datums, moisture definitions and reference conditions. Specific humidity uses moist-air mass as its denominator, whereas mixing ratio uses dry-air mass. A pressure-order flag differs from a temperature inversion, and a logarithmic-pressure weight can represent extrapolation.
Calculate a supplied logarithmic-pressure interpolation coordinate.
When to use this tool
Use Pressure Level Log Interpolation Weight when you already have pressure, firstPressure, secondPressure and need to calculate a supplied logarithmic-pressure interpolation coordinate.
How to use the tool and how it works
- Enter pressure, firstPressure, secondPressure. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read secondLevelWeight. Use the output convention below.
Require three positive pressures and different reference levels. Return log(p/p1)/log(p2/p1), with exact 0/1 at matching endpoints; use log1p of a finite relative gap where possible.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| pressure | Pressure | Required. Finite number; strictly above 0. |
| firstPressure | First Pressure | Required. Finite number; strictly above 0. |
| secondPressure | Second Pressure | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| secondLevelWeight | Log-pressure coordinate relative to first/second levels; extrapolation and reversed ordering are accepted. | Required. Finite number. |
{
"input": {
"pressure": 500,
"firstPressure": 1000,
"secondPressure": 250
},
"output": {
"secondLevelWeight": 0.5
}
}Limitations and assumptions
- Reversed reference order and extrapolation outside [0,1] are allowed. This returns a weight rather than an interpolated field or a verified atmospheric profile.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use calibrated profile and station data with the complete atmospheric model. Preserve datum, humidity and pressure conventions and assess uncertainty before interpreting local terms as an observed layer, state or forecast.
References
Similar or alternative tools
- Radiosonde Pressure Inversion Pair
Compare supplied upper- and lower-level pressures.
- Atmospheric Column Layer Dry Mass
Calculate a nominal dry-air column mass from supplied pressure bounds.