Syllabus Edition
First teaching 2015
Last exams 2025
Pathways of Energy Entering the Atmosphere
Written by: Alistair Marjot
Reviewed by: Bridgette Barrett
Pathways of Energy Entering the Atmosphere
When solar radiation (insolation) enters the Earth’s atmosphere, some of the energy becomes unavailable for ecosystems due to being:
Absorbed by inorganic matter
Reflected back into the atmosphere
This means very little of the sunlight available from the Sun is converted into biomass in ecosystems
About 51% of the available energy from the Sun never reaches producers
The pathway of radiation through the atmosphere involves a loss of radiation through reflection and absorption, with the following (approximate) percentage losses:
Reflection from clouds ~ 19%
Absorption of energy by clouds ~ 3%
Reflection by scatter from aerosols and atmospheric particles ~ 3%
Absorption by molecules and dust in the atmosphere ~ 17%
Reflection from the surface of the Earth ~ 9%
The ability of clouds and reflective surfaces on Earth (such as snow and ice) to reflect solar radiation is known as albedo
Of the 49% of solar radiation absorbed by the ground, only a small proportion ends up in producers
Most incoming solar radiation fails to enter chloroplasts in leaves because it is reflected, transmitted (passes straight through the leaf), or is the wrong wavelength to be absorbed
Of the radiation captured by leaves, only a small percentage ends up as biomass in growth compounds because the conversion of light to chemical energy is inefficient
In total, only around 0.06% of all solar radiation falling on Earth is captured by plants
From the sun to producers - the pathway of solar energy entering the atmosphere
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