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

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

Plymouth, England Kiev, Ukraine

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 Mountains  Elevation  1,000 ft. increase = 3.5°F decrease or -1°C/100m increase  Mountains  Orographic effect  Windward side – high precipitation  Leeward side – rain shadow

Elevation and Mountains

Frontal Precipitation

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)