Lecture 1 - Energy and the Earth System

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  • Created on: 03-05-21 10:28
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  • Atmospheres Lecture 1 - Energy and the Earth System
    • Weather vs climate
      • Both measured by the same quantity
      • Weather - day to day condition of the atmosphere (incl. temperature, rainfall and wind)
        • Deterministic view of the atmosphere
          • Can only be predicted up to 20 days in advance theoretically
      • Climate - avg. weather conditions of a place (incl. temperature, rainfall and wind)
        • Statistics based (can be done on longer timescales, if you know the boundary conditions for the climate system)
          • Because you're interested in the development of the temperature means and variability
        • Can be defined qualitatively (expected weather) or quantitatively(mean, variances, tendencies)
      • Climate variability - the overall distribution of climatological parameters (air pressure, temperature, precipitation, ice cover, sea surface temp.) bounded by weather extremes
        • Climate varies based on location - places on the coast e.g. San Francisco will experience air masses which will influence the temperature variations.
    • Climate
      • Open system, made up of spheres which interact with each other
        • Biosphere
        • Hydrosphere
        • Geosphere
        • Atmosphere
        • Cryosphere
      • Sources of energy
        • Solar radiation
        • Geothermal
        • Burning fossil fuels
        • Full moon radiation
        • Radiation from stars
    • Radiation
      • Properties
        • Electromagnetic waves which can travel through empty space
        • Characterised by wavelength
        • Transfers energy but doesn't displace or transport matter
        • Moves at a constant speed (of light) regardless of frequency/wavelength
        • The higher the frequency, the higher the energy
        • Only form of energy that can't travel through space without matter
      • The Sun and Solar Radiation
        • Encompasses a range of wavelengths: ultraviolet, visible and infrared
        • Radiation emitted from the Sun's photosphere
        • A fraction of  solar radiation emitted from the Sun drives climate system
        • Sun creates energy through nuclear fusion
      • Emission
        • All matter with a temp. above absolute zero emits radiation (i.e. every real body emits)
        • Black body - perfect absorber and emitter (e.g. Sun)
          • Planck's Law describes black body emission
            • Planck's Law - spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T, when there is no net flow of matter or energy between the body and its environment
        • The hotter an object, the smaller the wavelengths, the more radiation emitted
        • Stefan-Boltzmann Law
          • the total radiant heat power emitted from a surface is proportional to the fourth power of its absolute temperature


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