UHI formula (Heat Overlay): Difference between revisions
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The Urban heat island effect is calculated using the following formula:<br> | The Urban heat island effect is calculated using the following formula:<br> | ||
UHI<sub>max</sub> = ( 2 - S<sub>vf</sub> - F<sub>veg</sub> ) * ( S * (T<sub>max</sub>-T<sub>min</sub>)<sup>3</sup> / U )<sup>-4</sup> <br> | |||
UHI<sub>max</sub> = ( 2 - S<sub>vf</sub> - F<sub>veg</sub> ) * ( S * (T<sub>max</sub>-T<sub>min</sub>)<sup>3</sup> / U )<sup>-4</sup> | where: | ||
* S<sub>vf</sub> is the calculated average sky view factor; | |||
* F<sub>veg</sub> is the calculated average vegetation fraction; | |||
* S is | |||
==Analysis== | |||
The formula has two parts, the factor and the temperature effect:<br> | |||
UHI<sub>max</sub> = factor * temperature_effect<br> | |||
====Factor==== | |||
The factor is influenced by the sky view factor and the vegetation fraction, both ranging from 0 to 1. When both are low, i.e. barely any sky and no vegetation, the factor is near 2. When both are high, i.e. no surrounding buildings and a lot of vegetation, the factor is near 0. | |||
====Temperature effect==== | |||
The S is calculated as followed: | |||
S = R<sub>avg</sub> / (C<sub>air</sub> * ρ<sub>air</sub>) | |||
Revision as of 13:15, 11 September 2019
The Urban heat island effect is calculated using the following formula:
UHImax = ( 2 - Svf - Fveg ) * ( S * (Tmax-Tmin)3 / U )-4
where:
- Svf is the calculated average sky view factor;
- Fveg is the calculated average vegetation fraction;
- S is
Analysis
The formula has two parts, the factor and the temperature effect:
UHImax = factor * temperature_effect
Factor
The factor is influenced by the sky view factor and the vegetation fraction, both ranging from 0 to 1. When both are low, i.e. barely any sky and no vegetation, the factor is near 2. When both are high, i.e. no surrounding buildings and a lot of vegetation, the factor is near 0.
Temperature effect
The S is calculated as followed: S = Ravg / (Cair * ρair)