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 ($S_{frontal}$) on next tree even when distance between them is a single cell.

DPRA Improved: Wind impact ($S_{frontal}$) 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 because all trees then become a single polygon without space between them.
• See Wind calculation model for more details.

See also

• Wind calculation model

API Endpoints

• Api session event editor overlay set attribute

---

Heat Stress Module

Heat Stress Module

Tutorials

Overview

Theory

Benchmarks

Group

Model attributes

Model attributes

Daily average radiation • Daily average wind speed • Daily maximum temperature • Daily minimum temperature • Dates • Exclude buildings • Exclude water • Exclude foliage height m • Foliage areas • Hourly humidity • Hourly radiation • Hourly temperature • Max shadow distance • Sun altitude • Sun azimuth • Sun daily motion • Wind direction • Wind speed • Wind decline angle

Group

Feature attributes

Building attributes

Bowen ratio • Foliage height • Foliage crown factor • Vegetation fraction

Terrain attributes

Bowen ratio •  Vegetation fraction

Area attributes

Foliage height

Group

Prequels

Prequels

Building elevation • Foliage height • Terrain elevation

Related

Calculation models and formulas • Feature attributes • Model attributes • Result types