Causes of Weather

Chapter 12Section 1

Meteorology

• Study of atmospheric phenomenon• Meteor– Anything high in the sky• Rain droplets• Clouds• Rainbows• snowflakes

Weather vs. Climate

Weather• Short-term atmospheric

phenomena that interact and interfere in the environment

Climate• Long-term average of

variations in weather for a particular area

Heating Earth’s Surface

• Imbalanced heating– Earth’s axis of rotation is tilted relative to the

plane of Earth’s orbit

Thermal Energy Redistribution

• Areas maintain the same average temperatures over time due to the constant movement of air and water over the surface.

• Weather moves thermal energy over the planet.

Air Masses

• Conduction- warm air rises and cool air sinks

• Warm air is less dense than cool air

• Air Mass: – A large volume of air

that has the same characteristics of its source region.

Tropical Air Masses• Maritime tropical air originates over bodies of water

– Gulf of Mexico– Caribbean Sea– Tropical and subtropical Atlantic and Pacific Oceans– Brings hot humid weather to eastern 2/3 of North America

• Continental Tropical Air originates in Mexico and Southern United States.– Hot and dry

Polar Air Masses• Maritime Polar Air Masses– Form over cold waters of the North Atlantic and

North Pacific

Polar Air Masses

• Continental Polar Air Masses for over the interior of Canada– Cold frigid temperature

in winter– Brings relief to hot

summers

Arctic Air Masses

• Arctic Air Masses originate over snow covered surfaces above 60⁰ N Latitude– Areas get almost no

solar radiation– Extremely cold

especially during the winter

Air Mass Modification• Air masses move constantly• Thermal energy is

transferred from one area to another when they move

• Air masses can take on characteristics of another region as it travels over it

• Modification occurs when this happens– Thermal energy is exchanged

with the surface it travels over