GEOG 1112: Weather and Climate Global Energy System Sept 11, 2014

The Electromagnetic Spectrum Radiation – Electromagnetic (EM) energy transmitted as a wave

Shortwave Radiation Emitted by “hot” objects, i.e. the Sun, 6000ºC (10,382ºF) surface temperature Gamma radiation, X-rays, Ultraviolet, Visible light and Near-infrared Hot objects emit much more radiation at shorter wavelengths than cooler objects at longer wavelengths– Wein’s Law

Longwave Radiation Emitted by “cool” objects, i.e. those on Earth’s surface, even objects hot to the touch, or too hot to touch Avg temp of Earths surface 16ºC (61ºF) Thermal infrared wavelengths

Solar Radiation through Atmosphere Absorption – gases and particulates interrupt solar radiation, gain heat Reflection – radiation returns to space Scattering – redirection & deflection of radiation Transmitted (direct)– radiation reaches surface

Energy Pathways

Heat (Energy) Transfer Heat –a form of energy that flows from one system or object to another because the two are at different temperatures 4 ways to transfer heat: 1. Radiation – 2. Conduction – 3. Convection – 4. Advection –

Energy Pathways Insolation input –All radiation received at Earth’s surface – direct and indirect Scattering (diffuse radiation) –Changing direction of radiation’s movement, without altering its wavelengths –Pollutants, ice, and water vapor increase scattering –Why is diffuse radiation important?

Energy Pathways Scattering (diffuse radiation) –Rayleigh Principle – the shorter the wavelength, the greater the scattering; the longer the wavelength, the less the scattering –Shorter wavelengths of visible light (blues and violets) scatter the most and dominate the lower atmosphere –More blue present in sunlight, so the sky is blue –If we had NO atmosphere, what color would the sky be?

Energy Pathways Sunrise/Sunset –When the sun is low on the horizon, its rays must travel through more atmosphere –This increases scattering of shorter wavelengths (blues) so that only the longer wavelengths color the sky (oranges, reds)

Energy Pathways

Refraction – change in speed and direction of light –When a form of radiation moves from one medium to another (air to water, space to atmosphere), its speed and direction change –The wavelengths of radiation are bent into different angles, separating the light into its component colors –Rainbows – created when visible light passes through raindrops, is refracted, and reflected showing all colors Energy Pathways

Refraction

Mirage – an image that appears near the horizon where light waves are refracted by layers of air at different temperatures and densities on a hot day When the sun is low in the sky, its light must penetrate through more air – its refracted by layers of air at different temperatures and densities creating a mirage

Refraction