Huglin Heliothermal Index

Calculate Huglin mean/maximum heliothermal contributions over caller supplied season with caller latitude/daylength coefficient and base; no implicit hemisphere calendar or grape suitability classification.

Description

The Huglin index accumulates vineyard heat using both mean and maximum daily temperatures.

The Huglin index accumulates vineyard heat using both mean and maximum daily temperatures. A caller-supplied latitude or daylight coefficient adjusts the sum, while a base temperature excludes cooler contributions.^[1]

When to use Huglin Heliothermal Index

Use this tool to calculate Huglin mean/maximum heliothermal contributions over caller supplied season with caller latitude/daylength coefficient and base; no implicit hemisphere calendar or grape suitability classification.

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 Huglin Heliothermal Index 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 dailyMeanTemperaturesC, dailyMaximumTemperaturesC, callerBaseTemperatureC, callerLatitudeDayLengthCoefficient using the field table and calculation rules, then run the tool.
Read huglinDailyContributions, huglinIndex. 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
dailyMeanTemperaturesC	Daily mean temperatures c	list of number	Required
dailyMaximumTemperaturesC	Daily maximum temperatures c	list of number	Required
callerBaseTemperatureC	Caller base temperature c	number	Required
callerLatitudeDayLengthCoefficient	Caller latitude day length coefficient	number	Required

Supply aligned nonempty mean and maximum daily temperatures in °C, a finite base temperature and a positive latitude/daylight coefficient. Each maximum must be at least its corresponding mean. The tool clips each mean-of-mean-and-maximum excess at zero, multiplies by the coefficient and returns daily contributions and their total.

Paired lists must be nonempty and have equal lengths.

daily contribution = max[0, (Tmean + Tmax)/2 − base] × coefficient; index = Σ daily contribution

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

Output field	Meaning	Value type
huglinDailyContributions	Huglin daily contributions	list of number
huglinIndex	Huglin index	number

json

{
  "input": {
    "dailyMeanTemperaturesC": [
      10,
      20
    ],
    "dailyMaximumTemperaturesC": [
      20,
      30
    ],
    "callerBaseTemperatureC": 10,
    "callerLatitudeDayLengthCoefficient": 1.1
  },
  "output": {
    "huglinDailyContributions": [
      5.5,
      16.5
    ],
    "huglinIndex": 22
  }
}

Limitations and assumptions

No growing-season dates, default coefficient or regional class boundaries are built in. Choose the coefficient, base and seasonal observations consistently with the intended convention. The index does not predict ripening, yield or suitability by itself.

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 Winkler Index GDD Region Classifier: Resolve an already supplied seasonal GDD into caller Winkler-region policy bands, using lower-inclusive boundaries; no duplicate GDD accumulation, mutable region constants or crop recommendation. For a complementary task, use Growing Degree Days Single Sinusoid Method: Integrate ideal single-sinusoid daily temperature excess between caller lower and horizontal upper cutoffs analytically; differs from arithmetic daily-mean GDD and is not a development-event forecast.

References

Huglin Heliothermal Index — tool.io

Similar or alternative tools

Winkler Index GDD Region Classifier
Resolve an already supplied seasonal GDD into caller Winkler-region policy bands, using lower-inclusive boundaries; no duplicate GDD accumulation, mutable region constants or crop recommendation.
Growing Degree Days Single Sinusoid Method
Integrate ideal single-sinusoid daily temperature excess between caller lower and horizontal upper cutoffs analytically; differs from arithmetic daily-mean GDD and is not a development-event forecast.