Average calculation model (Heat Overlay): Difference between revisions

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The [[wind speed]] and [[direction]], measured at a weather station, are used to determine the window for averaging.  
The [[Wind speed (Heat Overlay)|wind speed]] and [[Wind direction (Heat Overlay)|direction]] are used to determine the window for averaging values around a cell. Commonly, the values at a reference [[weather station (Heat Overlay)|weather station]] are used. In calculations with a low wind speed, an cell-centered averaging window is used. In calculations with a high wind speed, an oblong rectangle is used for averaging, with the cell in question offset towards the far side along the line of the wind direction.
If the wind speed is:
* < 1.5 meter per second, the window is cell centered: 700x700;
* >= 1.5 meter per second, the window is 1100 x 500, centered as 1000 x 250 x 100 x 250, where the long edge 1000 is opposite of the wind direction.
[[File:Average_window_wind_(Heat_Overlay).png|thumb|350px]][[File:Average_window_nowind_(Heat_Overlay).png]]


The following parameters are averaged by this window:
Wind speed:
* Vegetation fraction, originating as the fraction green/vegetation present in Buildings and Terrains;
* < 1.5 meter per second, the window is square and cell centered
* Sky view factor, calculated by the Sky view factor calculation model;
* >= 1.5 meter per second, the window is oblong, and offset towards the wind direction, to account for the effect the wind has on factors which influence temperature.
 
The averaging
 
{|class=wikitable
! Window
! Model
! Low wind speeds
! High wind speeds
|-
| {{anchor|Large window|Large window}}
|
* [[Vegetation avg result type (Heat Overlay)|Vegetation fraction]], based on the fraction [[Vegetation fraction (Heat Overlay)|green/vegetation]] present in Buildings and Terrains
* [[Sky view avg result type (Heat Overlay)|Sky view factor]], calculated by the [[Sky view factor calculation model (Heat Overlay)|sky view factor calculation model]]
| [[File:Average window nowind (Heat_Overlay).png|250px|thumb|700x700 meters, cell-centered]]
| [[File:Average window wind (Heat Overlay).png|250px|thumb|1100x500 meters, centered at 1000x250x100x250]]
|-
| {{anchor|Small window|Small window}}
|
* [[Wind speed result type (Heat Overlay)|Wind speed]], based on the [[Wind calculation model (Heat Overlay)|wind direction]] configured as [[Wind speed (Heat Overlay)|wind speed]] parameter for the Overlay's calculation.
| [[File:Wind_window_sq(Heat_Overlay).png|250px|thumb|175x175 meters, cell-centered]]
| [[File:Wind_window_(Heat_Overlay).png|250px|thumb|280x140 meters, centered at 210x70x70x70]]
|}
 
{{article end
|seealso=
* [[Vegetation avg result type (Heat Overlay)|Vegetation fraction average result type]]
* [[Sky view avg result type (Heat Overlay)|Sky view factor average result type]]
}}
{{Template:HeatOverlay_formula_nav}}

Latest revision as of 17:01, 25 January 2023

The wind speed and direction are used to determine the window for averaging values around a cell. Commonly, the values at a reference weather station are used. In calculations with a low wind speed, an cell-centered averaging window is used. In calculations with a high wind speed, an oblong rectangle is used for averaging, with the cell in question offset towards the far side along the line of the wind direction.

Wind speed:

  • < 1.5 meter per second, the window is square and cell centered
  • >= 1.5 meter per second, the window is oblong, and offset towards the wind direction, to account for the effect the wind has on factors which influence temperature.

The averaging

Window Model Low wind speeds High wind speeds
Large window
700x700 meters, cell-centered
1100x500 meters, centered at 1000x250x100x250
Small window
175x175 meters, cell-centered
280x140 meters, centered at 210x70x70x70

See also

Heat Module
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Heat Module
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Tutorials
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Overview
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Theory
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Benchmarks
Group
Formulas
UHI • Temperatures • Diffuse radiation • PET
Calculation models
Foliage height • Sky view factor • Shade • Average vegetation and sky view factor
Related
Calculation models and formulas • Feature attributes • Model attributes • Result types


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