Wind decline angle (Heat Stress Overlay): Difference between revisions

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|unit=Degrees
|unit=Degrees
|description=This angle determines how the wind flows down around objects.  
|description=This angle determines how the wind flows down around objects.  
|defaultvalue=90
|defaultvalue=45
|icon=
|icon=
}}</onlyinclude>}}
}}</onlyinclude>}}
In the original {{Heat DPRA 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.
[[File:Wind_dpra.png|350px|thumb|left|DPRA: Wind has full impact (<math>S_{frontal}</math>) on next tree even when distance between them is a single cell.]]
[[File:Wind_improved.png|350px|thumb|right|DPRA Improved: Wind impact (<math>S_{frontal}</math>) on next tree is reduced producing more realistic results.]]
<br clear=all>


{{article end
{{article end
|notes=
|notes=
* By default the {{Heat DPRA Report}} does not take this effect into account and the value is set to 90 degrees (making it inactive).  
* Use a value of 90 to use the original {{Heat DPRA Report}} model.
* However a value of e.g. 45 degrees produces more realistic wind flow around objects.
* 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_(Heat_Stress_Overlay)#Improved wind model|Wind calculation model]] for more details.
|seealso= * [[Wind_calculation_model_(Heat_Stress_Overlay)#Improved wind model|Wind calculation model]]
|api=* [[Api session event editor overlay set attribute]]
}}
}}


{{HeatOverlay model attribute nav}}
{{HeatOverlay model attribute nav}}

Latest revision as of 12:02, 16 July 2026

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 (Sfrontal) on next tree even when distance between them is a single cell.
DPRA Improved: Wind impact (Sfrontal) 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.

See also

API Endpoints

Heat Stress Module
Heat Stress Module
Tutorials
Overview
Theory
Benchmarks
Group
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
Building attributes
Bowen ratio • Foliage height • Foliage crown factor • Vegetation fraction
Terrain attributes
Bowen ratio •  Vegetation fraction
Area attributes
Foliage height
Group
Prequels
Building elevation • Foliage height • Terrain elevation
Related
Calculation models and formulas • Feature attributes • Model attributes • Result types


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