GY205 Weather and Climate Lecture 2 (Please turn in homework on the table.)

Solar Radiation Interacting with the Atmosphere Absorption – some solar energy is absorbed, heating the atmosphere directly

Reflection – solar energy is redirected, not absorbed Most natural surfaces are diffuse reflectors, scattering energy Reflection and Scattering

Rayleigh Scattering Caused by gas molecules Energy scattered in all directions Mostly scatters shorter wavelengths

Mythbuster The sky is blue because air molecules scatter the blue wavelength of incoming visible light, NOT because the sky is reflecting the ocean.

Mie Scattering Caused by aerosols Most energy scattered forward Scatters all wavelengths Causes gray and hazy skies

Nonselective Scattering Caused by water droplets in clouds Scatters all wavelengths about equally Makes clouds white

Albedo Percentage of visible light reflected Earth’s albedo is 30%

Atmosphere Energy Balance Earth’s Energy Budget The amount of energy entering the atmosphere equals the amount of energy leaving

Global Warming The Greenhouse Effect

Shortwave radiation from the sun passes through the atmosphere and is absorbed by the surface, warming it The earth emits longwave radiation which is partially absorbed by “greenhouse gases” warming the atmosphere The atmosphere is mostly heated from below

Mythbuster The greenhouse effect is GOOD, without it earth would be freezing cold Increasing “greenhouse gases” is bad since more energy is absorbed in the atmosphere, and the result is global warming

Heat Sensible heat – heat that you can sense Latent heat – heat stored and released during phase changes

Water Phase Changes

Temperature Not the same as heat Measure of average kinetic energy of molecules in a substance A cup of coffee may have a higher temperature than the ocean, but the ocean contains much more heat

Influences on Temperature Latitude Altitude Cloud cover Large bodies of water Ocean currents Slope aspect Vegetation Time of day

Temperature Gradients Changes in temperature with distance Isotherms – lines of equal temperature

Thermometers Mercury or alcohol Bimetallic strip Thermistors

Wind Chill Temperature Index

Pressure Air has mass and weight Gas molecules are in motion Pressure is the force these molecules exert on a surface Sea level pressure is 14.7 psi, 29.92”Hg, or mb

Temperature and Pressure CoolerWarmer

Mass of Air and Pressure

Pressure Decreases with Altitude

Barometers Used to measure pressure Mercury or aneroid type

Horizontal Pressure Gradient Changes in pressure with distance Caused by uneven heating of earth’s surface Isobars – lines of equal pressure

Wind Differences in pressure result in the pressure gradient force The PGF starts the wind blowing Wind blows away from areas of higher pressure and toward areas of lower pressure

The Coriolis Effect An object traveling in a straight line across a rotating surface appears to curve relative to the surface

Coriolis Force

Mythbuster The Coriolis effect does NOT cause the water to flow down a drain one way or the other.

Frictional Force Force that opposes motion between objects that are touching Stronger nearer the surface Lowers wind speed Reduces Coriolis effect Affected by surface roughness

Wind Pattern Development

Pressure Systems and Wind Cyclones are low-pressure systems

Anticyclones are high-pressure systems

Cyclones and Anticyclones

Troughs and Ridges Troughs form around low-pressure systems Ridges form around high-pressure systems

Measuring the Wind Wind direction is always given as the direction the wind is blowing from Wind vane – points into the wind Anemometer – measures wind speed Aerovane – measures both

GY205 Weather and Climate End of Lecture 2