Fraction of albedo taken into account

What it is

The share of the ground-reflected light the model counts when a horizon profile is present. The ground between the array and a close obstacle, such as trees or buildings, receives less sunlight than open ground, so it reflects less. The model multiplies the horizon's ground-reflection factor by this value: at 1 the ground-reflected light is reduced only by the height of the skyline, at 0 none of it is counted. It acts only with a horizon profile and the crossing-fraction far-shading method.

Typical values and how to get it

1 for a distant skyline such as hills or mountains. Lower it when the skyline is made of close obstacles. If not given: 1: the height rule alone sets the ground light in front of the horizon.

How it is applied

$$G_{\text{alb,after}} = f_{\text{alb}}\,F_{\text{hrz}}\,G_{\text{alb}}$$

where

Symbol	Meaning	Unit
$G_{\text{alb,after}}$	the ground-reflected light on the plane after the horizon	W/m²
$f_{\text{alb}}$	this input	—
$F_{\text{hrz}}$	the horizon's ground-reflection factor: 1 for an open horizon, falling linearly to 0 for a skyline 20° high, averaged over the ground the plane sees	—
$G_{\text{alb}}$	the ground-reflected light on the plane after transposition	W/m²

API

site.horizon_albedo_fraction

Symbols follow the symbol registry.