Precipitation Seasonality CV
Report measured twelve-month precipitation seasonality under population monthly SD, not sample SD or silently smoothed/+1 precipitation; zero mean leaves CV undefined.
Description
Precipitation seasonality can be summarized by the spread of monthly totals relative to their average.
Precipitation seasonality can be summarized by the spread of monthly totals relative to their average. A coefficient of variation is zero for equal monthly rainfall and grows as rainfall becomes more concentrated in particular months.1
Report measured twelve-month precipitation seasonality under population monthly SD, not sample SD or silently smoothed/+1 precipitation; zero mean leaves CV undefined.
When to use Precipitation Seasonality CV
Use this tool to report measured twelve-month precipitation seasonality under population monthly SD, not sample SD or silently smoothed/+1 precipitation; zero mean leaves CV undefined.
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 Precipitation Seasonality CV 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 monthlyPrecipitationMm using the field table and calculation rules, then run the tool.
- Read monthlyPrecipitationMeanMm, populationMonthlyPrecipitationSdMm, precipitationSeasonalityCvPercent. 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 |
|---|---|---|---|
| monthlyPrecipitationMm | Monthly precipitation mm | list of number | Required |
Supply exactly twelve nonnegative monthly precipitation totals in mm. Their mean must be positive. The tool computes the population standard deviation with denominator twelve, not the sample denominator eleven, and returns that standard deviation, the monthly mean and the coefficient of variation as a percentage.
mean = Σ P_month/12; SD = sqrt[Σ(P_month − mean)²/12]; CV_percent = 100 SD/mean Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| monthlyPrecipitationMeanMm | Monthly precipitation mean mm | number |
| populationMonthlyPrecipitationSdMm | Population monthly precipitation sd mm | number |
| precipitationSeasonalityCvPercent | Precipitation seasonality cv percent | number |
{
"input": {
"monthlyPrecipitationMm": [
0,
0,
0,
0,
0,
0,
20,
20,
20,
20,
20,
20
]
},
"output": {
"monthlyPrecipitationMeanMm": 10,
"populationMonthlyPrecipitationSdMm": 10,
"precipitationSeasonalityCvPercent": 100
}
}Limitations and assumptions
The statistic ignores which months are wet and does not distinguish two patterns with identical distributions of monthly totals. It is not an interannual variability estimate. An all-dry year is rejected because the relative variation would divide by zero.
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 Oceanity Conrad Index: Report named Conrad range/latitude-offset continentality and explicit 100-minus complementary oceanity convention; not clamped percentages or an independently validated maritime-climate probability. For a complementary task, 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.
References
-
Precipitation Seasonality CV — tool.io
Similar or alternative tools
- Oceanity Conrad Index
Report named Conrad range/latitude-offset continentality and explicit 100-minus complementary oceanity convention; not clamped percentages or an independently validated maritime-climate probability.
- 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.