Description
Calculate supplied measured-minus-background gas mixing ratio.
Gas and aerosol records need explicit species, charge, reference state, concentration and wet/dry bases. A pressure correction to mass concentration differs from a change in mole fraction, and absolute uncertainty differs from a relative percentage. Blank-corrected negative values can expose discrepancies without proving physical concentrations.
Calculate supplied measured-minus-background gas mixing ratio.
When to use this tool
Use Trace Gas Background Excess when you already have measuredMixingRatio, backgroundMixingRatio and need to calculate supplied measured-minus-background gas mixing ratio.
How to use the tool and how it works
- Enter measuredMixingRatio, backgroundMixingRatio. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read excessMixingRatio. Use the output convention below.
Return measuredMixingRatio-backgroundMixingRatio, preserving signs.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| measuredMixingRatio | Measured Mixing Ratio | Required. Finite number. |
| backgroundMixingRatio | Background Mixing Ratio | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| excessMixingRatio | Excess Mixing Ratio | Required. Finite number. |
{
"input": {
"measuredMixingRatio": 420,
"backgroundMixingRatio": 410
},
"output": {
"excessMixingRatio": 10
}
}Limitations and assumptions
- Both ratios need matching species, amount/mass basis and units. No background is estimated, plume identified or source attribution established.
- 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
Review the complete sampling, calibration and chemical analysis with verified reference conditions. Check dilution, background, charge and uncertainty definitions before using local terms in an emissions, composition or compliance assessment.
References
Similar or alternative tools
- Aerosol Blank Mass Subtraction
Subtract a supplied blank gain from filter mass gain.
- Canister Dilution Factor Crosswalk
Correct a supplied pressure-diluted canister concentration for diluent background.