Trewartha Climate Classifier

Trewartha main thermal groups using the Patton dry threshold 10(2.3T−0.64Ps+41), with Ps the summer precipitation percentage. Requires twelve homogeneous monthly normals and explicit hemisphere. Does not implement subclasses, establish mapped climate identity or predict future climate.

Description

Trewartha-style groups combine temperature seasonality with an aridity criterion.

Trewartha-style groups combine temperature seasonality with an aridity criterion.^[1]

The adopted thresholds and hemisphere convention determine this tool's bounded classification. Use Trewartha Climate Classifier to evaluate the supplied inputs under the model explained below.

When to use Trewartha Climate Classifier

Use Trewartha Climate Classifier to evaluate the supplied inputs under the model explained below. Establish the units, measurement scope and model assumptions before entering values.

How to use Trewartha Climate Classifier and understand its results

Establish the units, measurement scope and model assumptions before entering values.
Enter Monthly temperature c, Monthly precipitation mm, Northern hemisphere using the field table and validation rules below, then run the tool.
Read Trewartha thermal group, Months at least ten c, Caller model dry threshold mm; interpret the units, signs, ordering and unknown-value placeholders described below.
Correct reported input errors and rerun. Apply successful results according to their specific meanings and check the assumptions before using them in a decision.

Input field	Meaning	Value type	Requirement
monthlyTemperatureC	Monthly temperature c	array of number	Required; constraints below
monthlyPrecipitationMm	Monthly precipitation mm	array of number	Required; constraints below
northernHemisphere	Northern hemisphere	boolean	Required; constraints below

Enter exactly twelve finite temperature normals in °C and twelve nonnegative precipitation normals in mm, ordered January to December, plus a hemisphere boolean. Summer is April–September in the north and October–March in the south. Summer rain percentage is 50 when annual rain is zero. Compute dry threshold 10×(2.3×meanTemperature−0.64×summerRainPercent+41). Annual rain below it gives B; otherwise all months at least 18°C gives A, then months at least 10°C give C for 8 or more, D for 4 or more, E for 1 or more and F for none. Return the group, warm-month count and threshold. This is the committed thermal/dry model without further subclasses.

dryThresholdMm=10×(2.3×Tmean−0.64×summerRainPercent+41); warmMonths=count(T≥10)

Use the field order, units and branch conditions described above.

Output field	Meaning	Value type
trewarthaThermalGroup	Trewartha thermal group	string
monthsAtLeastTenC	Months at least ten c	number
callerModelDryThresholdMm	Caller model dry threshold mm	number

json

{
  "input": {
    "monthlyTemperatureC": [
      25,
      25,
      25,
      25,
      25,
      25,
      25,
      25,
      25,
      25,
      25,
      25
    ],
    "monthlyPrecipitationMm": [
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100,
      100
    ],
    "northernHemisphere": true
  },
  "output": {
    "trewarthaThermalGroup": "A",
    "monthsAtLeastTenC": 12,
    "callerModelDryThresholdMm": 665
  }
}

Limitations and assumptions

The adopted thresholds and hemisphere convention determine this tool's bounded classification. Apply the exact scope and assumptions explained above.

All listed fields require explicit values. Unexpected fields, incorrect types, nonfinite numbers and sparse arrays fail validation. Domain-specific bounds, alignments and supported tokens are explained above; extremely large inputs or outputs can also be rejected. Input errors differ from successful false results, empty match lists and unknown-evidence placeholders.

Alternative or Complementary methods

Use Koppen Climate Class Classifier for a related task: A Köppen-style classifier uses monthly temperature and precipitation normals and a hemisphere convention.

Use Holdridge Life Zone Classifier for a related task: Holdridge-style comparisons locate biotemperature and rainfall in a logarithmic reference plane.

References

Trewartha Climate Classifier — tool.io

Similar or alternative tools

Koppen Climate Class Classifier
A Köppen-style classifier uses monthly temperature and precipitation normals and a hemisphere convention.
Holdridge Life Zone Classifier
Holdridge-style comparisons locate biotemperature and rainfall in a logarithmic reference plane.