Weather and Climate

Chapter 3

Factors Affecting Climate

Section 1

The Sun and Latitude•Latitude/Climate Relationship

– Middle and High: distinct seasons– Low: warm all year– Polar: cold all year

•Sun’s Radiant Energy– ½ reflected or absorbed by atmosphere,

½ absorbed by Earth’s surface– Greenhouse effect

•Earth’s air slows rate of heat escape into space

The Sun and Latitude•Global warming: fossil fuel

emissions?– Emissions from fossil fuels’ combustion

produces carbon dioxide– Carbon dioxide absorbs and retains

heat in Earth’s atmosphere– Scientists divided

•Some argue that temp. increased due to human/environment interaction

•Some argue that warming trend is a natural occurrence

– Ample evidence on both sides of the argument…decide for yourself

The Sun and Latitude

The Sun and Latitude

Atmospheric Pressure•Increase in altitude = decrease in pressure

•Heating and cooling of air causes changes in atmospheric pressure– Warm air rises = low pressure– Cooled air drops = high pressure

Atmospheric Pressure•Centers of low pressure, warm air rising (cyclones) = unstable, stormy weather

•Centers of high pressure, cold air dropping = stable, clear, dry weather

Atmospheric Pressure•Four major air pressure zones– Equatorial low– Subtropical highs– Subpolar lows– Polar highs

Global Wind Belts

Prevailing Winds

Global Winds Animation

Global Wind Belts•Prevailing Winds

– Doldrums•Equatorial zone – little to no wind

– NE Trade Winds– Westerlies

•Middle latitudes – west-to-east flow– Polar Easterlies

•Eastward flow from polar to middle latitudes

•Fronts – Two air masses of widely different

temp. or moisture level meet; precipitation results

Global Wind Belts•Jet Stream

–Prevailing winds in upper atmosphere•Up to 300 mph

Oceans and Currents

•Currents moderate the effects of latitude on climate–Water heats and cools more slowly than land

–Landforms near currents experience the currents effects

•Gulf Stream/North Atlantic Drift

Oceans and Currents

Oceans and Currents

Oceans and Currents

•Plymouth, England• http://www.worldclimate.com/cgi-bin/data.pl?

ref=N50W004+1102+03827W

•Kiev, Ukrainehttp://www.worldclimate.com/cgi-bin/data.pl?ref=N50E030+1102+33345W

1

Distributing the Sun’s Heat

Weather Factors

Section 2

Precipitation•Forms of precipitation

– Rain– Snow– Sleet– Hail

•Persistent in low-pressure zones

•Lowest in high-pressure zones

Elevation and MountainsElevation

1,000 ft. increase = 3.5°F decrease or -1°C/100m increase

MountainsOrographic effect

Windward side – high precipitation

Leeward side – rain shadow

Elevation and Mountains

Elevation and Mountains

Frontal Precipitation

Storms

Storms

Storms

Storms

Storms

Climate and Vegetation Patterns

Section 3

Climate and Vegetation•Dry (Arid) Climates

–Arid•Found at about 30° N & S latitude, sometimes on W coasts of continents

•Subtropical high-pressure zone•<10” of annual precip.

–Semiarid•Transition zone between arid and humid regions

•Grain-growing areas (American Great Plains)

Arid & Semiarid

Climate and Vegetation•Middle-Latitude Climates

–Mediterranean•Found on coastal areas of S Europe or W coasts of continents w/cool ocean currents

–Semiarid•Transition zone between arid and humid regions

•Grain-growing areas (American Great Plains)