The Earth’s Atmosphere

The Atmosphere The higher you climb, the less dense the air becomes. Why? It also becomes colder. Why is the atmosphere important to us?

Atmospheric Pressure As your altitude increases, the density of the air decreases. The gas molecules spread farther apart and collide less often. Therefore, the atmospheric pressure decreases.

What happens to the sun’s energy when it reaches Earth? Absorbed = 50 + 20 = 70% Reflected = 5 + 25 = 30%

The Greenhouse Effect Visible light, infrared radiation, and UV light come from the sun. As the surface warms it emits IR. The infrared is reradiated back by greenhouse gases, increasing the surface temperature even further. Without this effect the average temperature would be -15oC.

Conduction: transfer of heat through contact, or when molecules bump into one another. Convection: the transfer of heat by the flow of a heated material. Convention occurs in gases and liquids. Hot air will rise as it is pushed up by sinking cold air.

Local Winds Sea Breezes: During the day, land heats up faster than water, and the land radiates heat and warms nearby air. Warm air rises and is replaced by cold air from over the water. Wind blows from the sea towards the land. Land Breeze: At night, warm air from over the water rises up and cold air from the land moves in to replace it. Wind blows from the land towards the sea.

Global Winds Coriolis Effect – the spin of the Earth makes winds curve. Trade Winds – E to W, towards the equator. Polar Easterlies – E to W, away from the poles. Prevailing Westerlies – W to E, away from equator and towards the poles. Jet Streams – a fast moving river of air in the upper atmosphere, from W to E, with a changing latitude