Radiation, Insolation, and Energy Transfer

Solar Radiation: Sun to Earth Speed of light: 300,000 km/second (186,000 miles/sec.) Distance to Earth: 150 million km (93 million miles) Radiation reaches us in about 8.3 minutes

Radiation Radiation: energy transferred in the form of electromagnetic waves –no transfer of matter –no material medium needed Solar Constant = 2 calories/cm 2 /minute

Classifying Radiation Classified based on wavelength,

The Electromagnetic Spectrum Micrometers or microns (µ) = 1/ or or Hence Microwaves are about 1mm - long. Radio waves are about a meter to 1000 meters long.

Insolation The sun’s energy distribution: UV and shorter = 7% Visible light = 50% Infrared (IR) = 43% Thermal Infrared, the longest infrared, = heat. Microwaves (1 mm – 30 cm) are used for long distance communications. Radar is portion of microwave. Microwave cooking discovered on Navy ships. Takes 1/2 the energy of conduction or convection ovens - more efficient. Why doesn’t microwave pass through window of oven? Gamma - used for food safety. Discovered after nuclear blasts.

Radiation Laws All objects emit radiation. Hot objects emit more radiation (per unit area) than cold objects. less radiationmore radiation

Radiation Laws (Wein’s Law) The hotter the radiating body, the shorter the wavelength of maximum radiation. Sun: 6000ºC (11,000ºF) Earth: 15ºC (60ºF)

Getting through the atmosphere: Energy pathways and principles Transmission Scattering Reflection Absorption Refraction

Transmission Energy is passed through the atmosphere Energy/heat provided to the Earth system Direct radiation

Scattering Energy “bounces off” particles in the atmosphere. Backscattering (albedo) Scattering (diffuse radiation)

Scattering Rayleigh Scattering: selective scattering if dust is about 1/10 the wavelength of light (.5 micron) VIB G YOR 4x 1x 1. sun appears yellow as VIB is scattered out. 2. sky is blue: VIB is down-scattered and becomes prominent. Mie Scattering: white scattering, non- selective, occurs with bigger particles, about 30x the wavelengths of light. 1. salt crystals: things whiter at distance 2. bluer sky at high elevation - less white 3. white clouds.  distance,  scatter result? Scattering & light short,  scatter result?

Reflection Energy is bounced directly back out to space (energy loss to Earth’s system) Albedo (  ) reflective quality of a surface Light color  high  Dark color  low 

Absorption Energy is absorbed by the atmosphere or the surface Thermal (heat) energy created. ozone oxygen carbon dioxide water vapor liquid water / clouds

Refraction Change in direction direction of radiation, by wavelength, in response to change in density of medium.

Refraction Change in direction direction of radiation, by wavelength, in response to change in density of medium.

Conduction Convection Adiabatic Cooling and Warming Latent Heat in Phase Changes of H 2 O Four Heat Transfer Mechanisms

Molecule to molecule energy transfer When molecules collide, higher energy molecules excite lower temperature molecules, thereby transferring kinetic (heat) energy. Conduction

Heat is transferred by the movement, from place to place, of a gas or liquid. The principal motion is vertical. All heated gases and liquids experience this kind of “mixing” heat exchange. Convection

When air rises it expands and cools as its pressure is decreased. Thus, when it descends, it is warmed, as pressure increases. This change takes place without the addition or subtraction of energy from another source. Adiabatic Cooling and Warming

Ice 80 calories/gram Water 585 calories/gram Water Vapor Phase Changes (Latent Heat) Releases Energy Stores Energy Freezing Condensation Melting Evaporation Sublimation

30 Units 64 Units Longwave 22 Latent Heat 6 Units 48 Units 64 Units 14 Units Greenhouse 6 Units Conduction/ Convection 19 direct absorb 3 Ozone 100 Units 100 Units Outgoing

Key Points Electromagnetic radiation and spectrum Radiation laws and solar radiation Energy pathways and transfer principles Earth energy budget