R95p Heavy Precipitation Fraction

Compute R95p share on strict exceedance of a caller independently established baseline wet-day 95th percentile; ties are not exceedances and the analysis period is not silently its own baseline.

Description

The very-wet-day precipitation fraction measures how much wet-day rain falls on days exceeding a supplied high-percentile threshold.

The very-wet-day precipitation fraction measures how much wet-day rain falls on days exceeding a supplied high-percentile threshold. It describes concentration of rainfall in unusually wet days rather than the fraction of days that are unusually wet.^{[1, 2]}

Compute R95p share on strict exceedance of a caller independently established baseline wet-day 95th percentile; ties are not exceedances and the analysis period is not silently its own baseline.

When to use R95p Heavy Precipitation Fraction

Use this tool to compute R95p share on strict exceedance of a caller independently established baseline wet-day 95th percentile; ties are not exceedances and the analysis period is not silently its own baseline.

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 R95p Heavy Precipitation Fraction 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 dailyPrecipitationMm, callerBaselineWetDay95thPercentileMm, callerWetDayThresholdMm using the field table and calculation rules, then run the tool.
Read heavyPrecipitationTotalMm, wetPrecipitationTotalMm, r95pFraction. 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
dailyPrecipitationMm	Daily precipitation mm	list of number	Required
callerBaselineWetDay95thPercentileMm	Caller baseline wet day95th percentile mm	number	Required
callerWetDayThresholdMm	Caller wet day threshold mm	number	Required

Supply nonnegative daily precipitation, a positive wet-day threshold and a supplied 95th-percentile threshold at least as large as the wet threshold, all in mm. Equality counts for the wet-day denominator, but a very wet day must strictly exceed the percentile threshold. The tool returns the two precipitation totals and their ratio. It rejects a zero wet-day total.

fraction = Σ P_i for P_i > percentile threshold / Σ P_i for P_i ≥ wet threshold

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
heavyPrecipitationTotalMm	Heavy precipitation total mm	number
wetPrecipitationTotalMm	Wet precipitation total mm	number
r95pFraction	R95p fraction	number

json

{
  "input": {
    "dailyPrecipitationMm": [
      0,
      1,
      3,
      6
    ],
    "callerBaselineWetDay95thPercentileMm": 3,
    "callerWetDayThresholdMm": 1
  },
  "output": {
    "heavyPrecipitationTotalMm": 6,
    "wetPrecipitationTotalMm": 10,
    "r95pFraction": 0.6
  }
}

Limitations and assumptions

No percentile or reference period is fitted here. Establish the climatological threshold independently and use compatible gauge and period conventions. The result is a proportion, not a percentage or count of extreme days.

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.

Alternative or Complementary methods

Use Simple Daily Intensity Index SDII: Compute SDII using observed precipitation only on wet days at caller inclusive threshold; zero observed wet days is undefined rather than inventing a daily intensity. For a complementary task, use Rainy Days Threshold Counter: Audit a supplied increasing rain-threshold policy over observed daily precipitation with coverage denominator; no missing-as-dry treatment or climate category lookup.

Further background: Climate extreme index definitions.

References

R95p Heavy Precipitation Fraction — tool.io
Climate extreme index definitions — Climdex

Similar or alternative tools

Simple Daily Intensity Index SDII
Compute SDII using observed precipitation only on wet days at caller inclusive threshold; zero observed wet days is undefined rather than inventing a daily intensity.
Rainy Days Threshold Counter
Audit a supplied increasing rain-threshold policy over observed daily precipitation with coverage denominator; no missing-as-dry treatment or climate category lookup.