Diffuse radiation formula (Heat Overlay): Difference between revisions

Latest revision as of 11:52, 13 September 2021

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

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

$Q_{d,t}=Q_{gl,t}\cdot f_{transmission,t}$

where,

$Q_{gl,t}$ is the amount of sun radiation at time t, measured at a weather station.
$f_{transmission,t}$ is the atmospheric transmission factor at time t.

The atmospheric transmission factor f_{transmission,t} is calculated as followed:

where $\tau _{a}$ is the atmospheric transmissivity. This is calculated as:

$\tau _{a}={\frac {Q_{gl,t}}{1367\cdot \sin(\phi _{t})}}$

where,

$Q_{gl,t}$ is the amount of sun radiation at time t, measured at a weather station.
$\phi _{t}$ is the sun altitude angle in ° at time t.
$1367$ is sourced from the DPRA Heat stress report.

@@ Line 1: / Line 1: @@
-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:
-<math>Q_{d,t} = Q_{gl,t} * f_{transmission,t}</math>
+<math>Q_{d,t} = Q_{gl,t} \cdot f_{transmission,t}</math>
 where,
@@ Line 15: / Line 15: @@
 !Condition
 |-
-|1
+|<math>1</math>
-|τ<sub>a</sub> <= 0.3
+|<math>\tau_a < 0.3</math>
 |-
-|1.6-2* τ<sub>a</sub>
+|<math>1.6 - 2 \cdot \tau_a</math>
-|0.3 < τ<sub>a</sub> < 0.7
+|<math>0.3 < \tau_a  < 0.7</math>
 |-
-|0.2
+|<math>0.2</math>
-| τ<sub>a</sub> >=0.7
+|<math>\tau_a >= 0.7</math>
 |}
-where τ<sub>a</sub> 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>
@@ Line 30: / Line 31: @@
 * <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>1367</math> is sourced from the {{Heat DPRA Report}}.
 {{Template:HeatOverlay_formula_nav}}