Record Low Margin Under Previous
Compare new observed low with all previous eligible extrema, retaining signed margin and strict record equality semantics; exposure/record homogeneity must be caller established.
Description
A low-record margin compares a new observation with the lowest value in an earlier comparison period.
A low-record margin compares a new observation with the lowest value in an earlier comparison period. A positive margin means the new value is lower, while a zero margin is a tie rather than a new record.1
Compare new observed low with all previous eligible extrema, retaining signed margin and strict record equality semantics; exposure/record homogeneity must be caller established.
When to use Record Low Margin Under Previous
Use this tool to compare new observed low with all previous eligible extrema, retaining signed margin and strict record equality semantics; exposure/record homogeneity must be caller established.
Prepare the climate observations and any independently chosen thresholds or model parameters. Confirm units, daily coverage, time order and the intended seasonal window.
How to use Record Low Margin Under Previous and understand its results
- Prepare the climate observations and any independently chosen thresholds or model parameters. Confirm units, daily coverage, time order and the intended seasonal window.
- Enter previousObservedExtremesC, newObservedExtremeC using the field table and calculation rules, then run the tool.
- Read previousRecordC, signedNewRecordMarginC, isStrictNewRecord. 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 |
|---|---|---|---|
| previousObservedExtremesC | Previous observed extremes c | list of number | Required |
| newObservedExtremeC | New observed extreme c | number | Required |
Supply a nonempty list of previous values and the new value in the same unit. The tool finds the previous minimum, computes the signed margin and returns a boolean flag based on a strictly positive margin. It preserves negative margins when the new value remains above the previous low.
previous low = min earlier values; margin = previous low − new value; new record = (margin > 0) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| previousRecordC | Previous record c | number |
| signedNewRecordMarginC | Signed new record margin c | number |
| isStrictNewRecord | Is strict new record | boolean |
{
"input": {
"previousObservedExtremesC": [
10,
15
],
"newObservedExtremeC": 9
},
"output": {
"previousRecordC": 10,
"signedNewRecordMarginC": 1,
"isStrictNewRecord": true
}
}Limitations and assumptions
The tool only compares the supplied observations. It does not check measurement quality, geographic coverage, station changes or whether the comparison period is complete. A true flag establishes a record within this dataset, not an independently verified historical record.
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. A successfully returned false flag is an evaluated outcome; its meaning is explained above.
Alternative or Complementary methods
Use Record High Margin Over Previous: Compare new observed high with all previous eligible extrema, retaining signed margin and strict record equality semantics; exposure/record homogeneity must be caller established. For a complementary task, use Warm Spell Duration Index WSDI: Calculate warm WSDI maximum-temperature spells against caller independently calibrated day-of-year percentiles with strict exceedance and minimum run; threshold ties excluded, gap-free coverage required.
References
-
Record Low Margin Under Previous — tool.io
Similar or alternative tools
- Record High Margin Over Previous
Compare new observed high with all previous eligible extrema, retaining signed margin and strict record equality semantics; exposure/record homogeneity must be caller established.
- Warm Spell Duration Index WSDI
Calculate warm WSDI maximum-temperature spells against caller independently calibrated day-of-year percentiles with strict exceedance and minimum run; threshold ties excluded, gap-free coverage required.