Precipitationthornthwaite Climate

GEOGRAPHY & CARTOGRAPHY CALCULATOR Precipitationthornthwaite Climate A precise tool.
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What is the Precipitationthornthwaite Climate & How does it work?

The Thornthwaite method estimates potential evapotranspiration (PET) from temperature data and day‑length information. It is widely used in climatology to assess water balance and to classify climates based on moisture availability.

First a heat index \(I\) is calculated from the twelve mean monthly temperatures \(T_i\) (°C):

I = \\sum_{i=1}^{12} \\left(\\frac{T_i}{5}\\right)^{1.514}
I = heat index (dimensionless)

From \(I\) an exponent \(a\) is derived:

a = 0.49239 + 1.792\\times10^{-2}I + 7.71\\times10^{-5}I^{2} + 6.75\\times10^{-7}I^{3}
a = temperature‑adjustment factor
The monthly PET (mm) is then:
PET_i = 16 \\left(\\frac{10T_i}{I}\\right)^{a}
PET_i = potential evapotranspiration for month i

Summing the twelve \(PET_i\) values gives the annual PET. The Thornthwaite moisture index, which classifies the climate, is the ratio of observed annual precipitation \(P\) to annual PET:

Moisture\ Index = \\frac{P}{\sum_{i=1}^{12} PET_i}
Moisture Index = climate moisture classification (higher = wetter)
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Results are for informational purposes only and do not constitute professional advice.