Chapter 2 Energy Balance in Climatology Atmosphere gets most of it’s energy from the sun

1. Chapter 2 Energy Balance in Climatology Atmosphere gets most of it’s energy from the sun Energy is concentrated in certain regions must be moved from one location to another Transference of Energy (E) is done by: Conduction- E transfer by molecular contact Convection- E transfer by motion Radiation- E transfer via electromagnetic transference

2. Kinds of Energy Radiation- the emission of energy on the form of waves Kinetic- energy due to motion = 1/2m x v2 Potential- Energy stored as position potentially converted to Kinetic Energy Chemical- Energy used or released in chemical reactions Atomic- Energy released from an atomic nucleus at the expense of its mass Electrical- Energy exerted as a force on objects with an electrical charge Heat- aggregate energy of motions of atoms and molecules

4. Solar Radiation: The driving factor Radiation (Electromagnetic • energy) released, absorbed & reflected by all things travels as both a particle and • a wave is affected by • - gravity, magnetism, and atmosphere composition, distance, angle of incidence provides Earth with an • external source of energy

5. Wavelength and frequency are inversely related to one another Wavelength (1/l)= (n) Frequency

6. Nature of radiative energy (Radiation) electromagnetic travels as waves and also acts like particle All things radiate energy a function of Temperature Stephan-Boltzman’s Law F = s T 4 Where F is radiation Flux s is a constant 5.67 x 10-8 W/m2K4 T is the temperature in ° Kelvin The hotter the object, the more energy it radiates F = (5.67 x 10-8) x (6000)4 = 73,400,000 W/ m2 :Sun F = (5.67 x 10-8) x (288)4 = 390 W/ m2 :Earth

7. In general, temperature of emitting body controls wavelength of outgoing energy hotter = shorter  cooler = longer  Wein’s Law allows us to predict which wavelength will be most abundant. lmax= 2897/T Example: Sun’s surface temperature is 6000° K lmax = 2897/6000 = 0.48mm Thus, most of sun’s energy should be at a wavelength of 0.48 mm

8. 0.48

9. Solar Structure Sun is a fusion reactor -smashes atoms of H into other atoms and makes new, heavier elements and releases a bunch of energy H + H = He + a lot of energy Has zones that are important to climatology Photosphere- visible part of the sun we see all the time (covered during a solar eclipse) Consists primarily of Hydrogen (90%) and Helium (10%) This is where the 6000° K temperature comes from Uneven heat distribution in the 300 km thick layer created by convection currents results in grainy appearance

11. Chromosphere A wide (up to 1,000,000 Km) but variable zone of burning gases above the photosphere The gases in this zone move at high velocities and travel outward from the Sun as the solar wind Also the zone within which sun spots and solar flares occur Sun spots are cooler regions on the Sun’s surface zones of intense magnetic disturbance Flares are explosive eruptions of atomic particles and radiation that extend outward for millions of miles and can influence stuff 100’s of millions of miles away

12. Sun spots Solar Corona Solar Photosphere

13. What happens to solar radiation? It decreases with distance traveled outward Inverse square law Frec = F (1/d2) where F = radiation from Sun Frec = Radiation received and d = distance from source d is in astronomical unit (AU) or distance from Sun to Earth = 1 Our distance from the sun controls how much solar energy we get from the Sun Frec is very small 1/2,000,000,000 of the total energy produced by the Sun Several things can happen to that incoming energy Reflection, Refraction, Scattering, Absorption

14. How much energy does the Earth receive? Earth---> <---Radius (d) <---Sun Imagine a sphere with a radius (d) the distance from the Earth to the center of the Sun = 1 AU

15. Position affects radiation too Tilted away=less radiation in North Far away=less radiation • • Titled toward= more radiation in North Titled toward= more radiation • •

16. Milankovitch Orbital variations Eccentricity - change of Earth’s orbit around the Sun from a Circle to an Ellipse. Timeframe: 100,000 years Obliquity- Change in the tilt of the Earth’s axis of daily rotation. Timeframe: 41,000 yrs Precession- the wobble of earths tilt or the change in the timing of the tilt of the Earth that forces the northern hemisphere toward the sun- at perihelion vs aphelion 22,000 - to 26,000 years These work with other systems in the earth to set the pace of climate change

18. Albedo * reflected radiation Albedo = ________________ incident radiation A measure of the amount of reflected radiation • Some things reflect radiation better than others • - "dry" or "cold" Snow & Ice = high albedo - water = moderate for visible, low for infrared - plants= moderate for visible Land absorbs and releases radiative energy • quicker than water

20. Reflection energy is bounced away without being absorbed or transformed Scattering energy is diffused or scattered into different wavelengths related to composition and thickness of atmosphere Absorption some gases and aerosols capture (absorb) energy energy is typically re-released as longer wavelength radiative energy Transmissivity The amount of radiation that actually gets through to the surface

21. Greenhouse effect Seen as a bad thing by the public because of biased or poorly produced media coverage Greenhouse effect is absolutely essential to Earth’s habitability Without some means to absorb, block, scatter or transform energy, the Earth would be barren. Atmosphere does all four things Most important among these is absorption of longwave (Earth-reemitted or transformed) radiation Various gases capture this energy which warms the Earth’s atmosphere