Lecture 1 - Energy and the Earth System (2)
- Created by: sikemi__
- Created on: 03-05-21 11:27
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- Lecture 1 - Energy and the Earth System
- Solar constant
- Solar energy flux received by the Earth outside of the Earth's atmosphere
- Earth receives around 1/4 of the solar constant per surface area
- Depends on total radiation emitted by the Sun and the Sun-Earth distance
- Geological timescales - Radiation emitted by Sun increases over time
- Decadal to centennial timescales - 11 years Sun cycle dominates changes in solar output
- Distribution of radiation at Earth's surface depends on angle between Earth's rotational axis and plane of orbit
- Variations in orbital parameters causes ice ages (along with other factors)
- Solar energy flux received by the Earth outside of the Earth's atmosphere
- Geometric effects and surface radiation
- Latitude effect
- Less heating at higher latitudes (changes across the year)
- Sun angle effect
- Light dissipation is greater at shallow angles
- Optical path effect
- Together, these lead to seasonal and daily cycles in the amount of solar radiation
- Sun shifts noon overhead position between 23.5 degrees N and S, producing seasons
- Latitude effect
- Earth's response to solar insolation
- Incoming energy = outgoing energy
- Keeps Earth from constantly cooling or heating
- Receives energy as shortwave radiation, heating planet
- Emits energy as long wave radiation, cooling planet
- Before energy is radiated back into space, it undergoes several transformations and redistributions between the subsystems, producing weather and climate
- Incoming energy = outgoing energy
- Albedo
- Amount of incoming radiation reflected by an object across all wavelengths
- 0 = total absorption (black body), 1 = total reflection (white body)
- Earth albedo = approx 0.3
- Solar radiation reflected by surface particles in atmosphere e.g. clouds and aerosols and also gas molecules (Rayleigh scattering)
- High over deserts and snow/ice
- Low over dense forests and oceans
- Solar constant
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