Diffuse radiation formula (Heat Overlay)

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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,

  • is the amount of sun radiation at time t, measured at a weather station.
  • is the sun altitude angle in ° at time t.