Wind decline angle (Heat Stress Overlay)

Icon	Attribute	Unit	Range	Description	Default value
	WIND_DECLINE_ANGLE	Degrees		This angle determines how the wind flows down around objects.	45

In the original DPRA Heat stress report, the frontal surface is estimated using simplified tree shapes that are aggregated into large woodland polygons and cannot be used for individual tree polygons.

To address this issue, an angle of 45 degrees can be applied to smooth the wind flow, leading to a more accurate representation of the frontal surface and producing more realistic values in wooded areas or parks.

DPRA: Wind has full impact ( $S_{f r o n t a l}$ ) on next tree even when distance between them is a single cell.

DPRA Improved: Wind impact ( $S_{f r o n t a l}$ ) on next tree is reduced producing more realistic results.

Notes

Use a value of 90 to use the original DPRA Heat stress report model.
Use a value of 45 for improved wind flow around individual polygon trees.
Note that this value has a minimal impact on large woodland/forest polygons or connecting tree foliage because all trees then become a single entity without space between them.
See Wind calculation model for more details.