Chapter 3 Weather and Climate Objectives How does

Chapter 3 Weather and Climate

Objectives • How does the sun affect Earth’s atmosphere • How do global wind belts affect weather and climate • How do the oceans and mountains affect weather and climate • What is the difference between weather, climate and temperature?

The Sun and Latitude • Latitude affects solar energy • Solar Energy is converted to heat • The measurement of heat is called temperature • Greenhouse effect vs Global Warming

Atmospheric Pressure • Air has weight • Hot air expands (less dense), and rises • As it rises, the water vapor forms clouds. • Low pressure= unstable conditions • AKA cyclones

Atmospheric Pressure • Cold air is dense and sinks • This creates high pressure • As it sinks, it becomes dry and hot • Stable weather = clear and dry

The Equatorial Low Pressure Trough • This area is in the Earth's equatorial region (0°-10° North and South) • Composed of warm, light, ascending and converging air. Because the converging air is wet and full of excess energy it expands and cools as it rises, creating the clouds and heavy rainfall that are prominent throughout the area.

Subtropical High-Pressure Located between 20° N/S and 35°N/S this is a zone of hot, dry air that forms as the warm air descending from the tropics becomes hotter. Because hot air can hold more water vapor, it is relatively dry. The heavy rain along the equator also removes most of the excess moisture. The dominant winds in the Subtropical high are called westerlies.

Subpolar Low-Pressure • This area is at 60° N/S latitude and features cool, wet weather. The Subpolar low is caused by the meeting of cold air masses from higher latitudes and warmer air masses from lower latitudes. In the northern hemisphere, their meeting forms the polar front which produces the low pressure cyclonic storms responsible for precipitation in the Pacific Northwest and Europe. In the southern hemisphere, severe storms develop along these fronts and cause high winds and snowfall in Antarctica.

Polar High-Pressure • These are located at 90° N/S and are extremely cold and dry. With these systems, winds move away from the poles in an anticyclone which descends and diverges to form the polar easterlies. They are weak however because there is little energy available in the poles to make the systems strong. The Antarctic high is stronger though because it is able to form over the cold landmass instead of the warmer sea.

Wind • Amazing power • High pressure to Low pressure • Prevailing winds are consistent • Middle latitude prevailing winds = westerlies • Doldrums= No wind

Windsurfing

Oceans and Currents • • • Land heats and cools slow Water heats and cools fast Currents are like rivers in the ocean Some carry warm water from_______ Some carry cold water from_____

Precipitation • • Most water evaporates from oceans Vapor in the air is called humidity. Higher the temp = potential for more vapor When temp drops = vapor forms into liquid Rain Snow Sleet Hail

Elevation and Weather • Temp drops 3. 5 for 1000 ft of elevation • Orographic effect – Windward side = wet – Leeward = warm and dry rain shadows

Storms • Very low pressure systems cause storms • Middle latitude = Thunderstorms or Tornadoes • Tropical storms are usually smaller because they lack cold air • Hurricanes and typhoons are the most destructive tropical storms. • Typhoons occur in the western Pacific

Tropical Climate • Tropical Humid – Equator • Always Warm • Daily Thunderstorms • Complex Tropical Rainforests here

Tropical Climates • Tropical Wet and Dry – Seasonal Changes – Warm Wet Summers, Cold Dry Winters • Without direct rays (winter) High pressure replaces low pressure and the season is dry

Dry Climates • Arid = Dry • Where? – 30 degrees North or South (latitude!!!!!) – High Pressure Zones – Rain Shadows – Land Locked • What? – Small desert sprouts • Semiarid • Where? – Transition Zone • What? – Grass and Grain

Middle Latitude • Mediterranean – Coastal Areas – Cool ocean currents – Long, Sunny, Dry Summers – Wet mild winters • Humid Subtropical Climate – Eastern Coasts- Warm ocean Currents – Hot Humid Summers • Humid Continental – Very changeable weather – 4 distinct seasons

Coniferous vs Deciduous • Coniferous – Green all the time • Deciduous- Loses leaves during fall or winter

High Latitude There are 3 Main climates • Subarctic Climate – Above 50 degrees latitude – Very Large Region – Short Summers – Below Freezing half of year • Tundra Climate – Coastal areas – Very Long Winters – Some places have frozen soil year round (permafrost) – Limited Vegetation

High Latitude • Ice Cap Climate – Polar Regions – Huge masses of snow and ice – Rich Marine ecosystems

Highland Climate (Mountains) • Temperatures change with elevation • Orographic Effect • Tree Line- too cold for trees • Snow year round on some mountains

Objectives • How does the sun affect Earth’s atmosphere • How do global wind belts affect weather and climate • How do the oceans and mountains affect weather and climate • What is the difference between weather, climate and temperature?