Diffuse radiation formula (Heat Overlay): Difference between revisions

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The diffuse radiation is an input parameter for the [[PET_formulas_(Heat_Overlay)|PET-formula]]
The diffuse radiation is an input parameter for the [[PET_formulas_(Heat_Overlay)|PET-formula]].


The diffuse radation Q<sub>d</sub> at time t is calculated using the following formula:
The diffuse radation Q<sub>d</sub> at time t is calculated using the following formula:
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|<math>\tau_a >= 0.7</math>  
|<math>\tau_a >= 0.7</math>  
|}
|}
where <math>\tau_a</math> is the atmospheric transmissivity. This is calculated as:<br>
where <math>\tau_a</math> is the atmospheric transmissivity. This is calculated as:
 
<math>\tau_{a} = \frac{Q_{gl,t}}{1367 \cdot \sin(\phi_t)}</math>
<math>\tau_{a} = \frac{Q_{gl,t}}{1367 \cdot \sin(\phi_t)}</math>


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* <math>Q_{gl,t}</math> is the amount of [[Hourly_radiation_(Heat_Overlay)|sun radiation]] at time t, measured at a weather station.  
* <math>Q_{gl,t}</math> is the amount of [[Hourly_radiation_(Heat_Overlay)|sun radiation]] at time t, measured at a weather station.  
* <math>\phi_{t}</math> is the [[Sun_altitude_(Heat_Overlay)|sun altitude angle]] in ° at time t.
* <math>\phi_{t}</math> is the [[Sun_altitude_(Heat_Overlay)|sun altitude angle]] in ° at time t.
* <math>1367</math> is sourced from the {{Heat DPRA Report}}.


{{Template:HeatOverlay_formula_nav}}
{{Template:HeatOverlay_formula_nav}}

Latest revision as of 11:52, 13 September 2021

The diffuse radiation is an input parameter for the PET-formula.

The diffuse radation Qd at time t is calculated using the following formula:

where,

  • is the amount of sun radiation at time t, measured at a weather station.
  • is the atmospheric transmission factor at time t.

Atmospheric transmission factor

The atmospheric transmission factor ftransmission,t is calculated as followed:

ftransmission,t Condition

where is the atmospheric transmissivity. This is calculated as:

where,