Weather and Climate•Weather is the condition of the atmosphere at any given time or place

•Climate is the weather conditions in an area averaged over along period of time.

Greenhouse Effect

• The Sun’s energy is transferred into heat energy by the Earth’s surface. The heat energy is trapped by the atmosphere an reradiated back to Earth keeping it warm.

Greenhouse Effect

Global Energy Exchange

• The Equator region receives more direct sunlight therefore more heat energy and the region is hot

• Polar regions receives less direct sunlight therefore less heat energy and the region is cold

• Wind Currents and Ocean Currents brings hot air to polar regions and cold air to tropical regions.

• Earth is always trying to stay in balance

Air Pressure

• Air Pressure is the measurement of the force exerted by air

• Air pressure creates the winds and ocean currents

• Unequal heating of the Earth’s surface causes air pressure differences

Convection Currents

• Unequal heating of the atmosphere causes convection currents.

• When air becomes warmer it expands and becomes lighter and rises. Creating a low pressure which is unstable conditions.

• Cold air is more dense and heavy and tends to sink. Creating high pressure which is stable conditions.

Convection Currents

4 Major Pressure Zones

1. Equatorial Low Pressure Zone

2. Subtropical High Pressure Zone

3. Subpolar Low Pressure Zone

4. Polar High Pressure Zone

Global Wind Belts

• Trade Winds: blow from subtropical high to the equatorial low pressure. Northeast in Northern Hemisphere, Southeast in Southern Hemisphere

• Doldrums located along the equator no wind.

• Westerlies: Prevailing winds blows mainly from the West. Found in the Mid-Lattitudes.

Global Wind Belts

• Polar Easterlies: Blow from the east coming from the northern or southern polar regions.

• Where the polar easterlies meet the westerlies fronts are created.

• A weather front is when two air masses of different temperature and moisture meet.

Global wind Belts

Global Wind Belts

Water Cycle

• Evaporation: water is changed from liquid to a gas

• Condensation: water vapor changes from a gas to a liquid

• Precipitation: water falling from the sky as rain, snow ,sleet, and hail

Water Cycle

Weather Systems

• Weather moves from west to east

• High pressure system cool stable air

• Low pressure system warm unstable air

• Low pressure system has fronts.

• Warm front leading edge

• Cold front trailing edge

• Along fronts is where storms take place

Weather Map 11/30/2011

Weather Map for Saturday