Atmosphere and Weather AP Environmental Science.

Origin of Modern Atmosphere original atmosphere surrounded the homogenous planet Earth and probably was composed of H and He second atmosphere evolved from gases from molten Earth –H2O, CO2, SO2, CO, S2, Cl2, N2, H2, NH3, and CH4 –allowed formation of oceans and earliest life modern Atmosphere –evolved after Cyanobacteria started photosynthesizing –oxygen produced did not reach modern levels until about 400 million years ago

Exosphere Thermosphere (Ionosphere) Mesosphere Stratosphere Troposphere Atmosphere Layers

Composition Nitrogen (N 2, 78%)Nitrogen Oxygen (O 2, 21%)Oxygen Argon (Ar, 1%) myriad of other very influential components are also present which include the Water (H 2 O, 0 - 7%), "greenhouse" gases or Ozone (O 3, %), Carbon Dioxide (CO 2, %),WaterOzoneCarbon Dioxide

Solar heating of earth Solar radiation strikes the earth at different angles based on the latitude. At high latitudes – near the poles the sun’s energy is spread out over larger area At low latitudes – near equator the sun’s energy is concentrated in a small area

Seasonal Changes Occur because the earth’s axis is tilted Creates opposite seasons in the northern and southern hemisphere Factor that determines global air circulation patterns

Heating the atmosphere Solar energy (UV radiation) is absorbed –Darker objects absorb more radiation than lighter objects which reflect radiation Albedo – ability to reflect light radiation Absorbed radiation converted to heat (infrared radiation) Heat radiates off object and warms surrounding air

Earth’s Warming Mechanism Greenhouse effect –Natural and Essential Process –Global Warming is a DESIRED result of the greenhouse effect –Without this process the earth would be uninhabitable An INCREASED RATE of Global Warming could cause global climate consequences

Greenhouse gases Contained in the upper troposphere –Carbon dioxide (CO 2 ) –Water Vapor (H 2 O) –Methane (CH 4 ) –Nitrogen Oxide (N 2 O) Form a barrier that reflects infrared radiation and traps it

Greenhouse Effect  UV radiation (short-fast wavelengths) from sun penetrates atmosphere  UV Radiation is absorbed by the earth surfaces  UV Radiation is converted to heat (infrared radiation – long-slow wavelengths)  Infrared radiation rises into the atmosphere  Long slow wavelengths cannot penetrate the greenhouse gases in atmosphere  Heat is trapped in troposphere warming the earth’s air and surface.

Circulation of air Recall Convection –Transfer of heat through a fluid –Energy warms the air – density decreases –Warm air rises –As air rises it cools – density increases –Cool air falls –repeats

Atmospheric circulation Uneven heating of the earth’s surface causes temperature differences Temperature differences create pressure differences Pressure differences cause air to move High pressure air moves and pushes low pressure air – WIND is generated

Coriolis effect Non Rotating Earth model –Winds would blow only from north pole to equator Rotating Earth model –Rotation of earth creates Coriolis Effect Deflection of actions due to earth’s rotation Northern Hemisphere rotate to the right Southern Hemisphere rotates to the left –Creates Atmospheric circulation cells and wind belts

Coriolis efffect

Wind Belts Three major wind belts created by Coriolis effect –60 – 90 degrees latitude Polar Easterlies – winds blow FROM the east –30 – 60 degrees latitude Westerlies – winds blow FROM the west –0 – 30 degrees latitude (equator) Trade Winds – blow from east to west

Air-Ocean Interaction Air circulation causes winds –Winds cause friction –Friction moves water Creates surface currents –Currents follow global wind patters –Currents are deflected by continents –6 major circular currents called “gyres ” Responsible for the movement of heat energy –moderates local climates Gulf stream – moderates eastern US and UK California Current – moderates California coast Brazilian current – moderates temps of southern South America

Ocean Currents Sea-surface temperature influences air temperature as the ocean exchanges heat with the overlying atmosphere. It also influences evaporation rates which are generally higher where sea-surface temperature is higher

Surface Currents 6 major currents – gyres – rotate clockwise in Northern hemisphere and counterclockwise in southern hemisphere due to coriolis effect

Deep Currents Uneven heating of earth by solar radiation results in different density of ocean water –Polar Region Low Temps and Presence of Ice creates Very Cold, Very Salty water with high density – sinks rapidly –Mid latitudes Moderate temps create water with lower density –Equator High temps create water with low density Dense Polar water sinks and pushes less dense water out of the way creating deep circulation current

Global conveyor belt transfers heat energy around the planet Through upwelling it exchanges nutrients with the surface water Deep ocean currents store carbon dioxide