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Which factors determine how much solar energy reaches an inland water body?
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Inland water ecosystem
Figure 1: Relationship between the density of pure water and temperature.
The amount of solar energy that reaches an inland water body is determined by a combination of atmospheric conditions, the geometry of the Sun, and the physical state of the water surface.
Key factors include:
- Atmospheric Conditions: The quantity and quality of solar radiation entering the water are significantly altered by cloud cover, fog, atmospheric dust, and the composition of atmospheric gases, all of which cause scattering and refraction of sunlight.1
- Sun Elevation Angle: The angle of the Sun relative to the horizon influences surface reflectance. When the Sun is at a high elevation, reflectance is generally lower; as the angle becomes more oblique, reflectance increases. Latitude plays a primary role in determining this elevation angle.1
- Surface Characteristics: The roughness of the water surface affects how much light is reflected. For a smooth surface, reflectance is lowest when rays are perpendicular. If the water is rough, reflectance increases when the Sun is high and decreases when the Sun is at a low elevation.1
- Ice Cover: The presence of ice acts as a barrier to energy exchange. During periods of ice formation and thickening, energy flows out of the water, while during decay, energy flows into the water.2