Section 12.1 – The Causes of Weather 8th Grade Earth and Space Science Class Notes

What is Meteorology? Study of atmospheric phenomena Meteorologist – scientist who studies atmospheric phenomena

Weather vs. Climate Weather – short-term variations in atmospheric phenomena Climate – long-term, average variations in atmospheric phenomena Determined by 30 year averages

Heating the Earth’s Surface Solar radiation is constantly heating some portion of the Earth’s surface. The way solar radiation is distributed ultimately determines weather.

Imbalanced Heating Earth’s axis is tilted to different parts of the Earth receive different amount of sunlight at different times of the year.

Imbalanced Heating The Earth is a sphere so different places on Earth are at different angles to the sun. Some places receive more direct, concentrated sunlight

Thermal Energy Redistribution Air and water are constantly moving among the Earth’s surfaces, oceans, and atmosphere. This constant circulation keeps the same average temperatures in a particular area over time.

Air Masses Air mass – large volume of air with the same characteristics Source region – area over which an air mass forms

Types of Air Masses

Tropical Air Masses Maritime tropical – form over tropical bodies of water In the summer they bring hot, humid weather to the eastern 2/3 of North America Continental tropical – form over the southwestern US and Mexico

Polar Air Masses Maritime polar air masses – form over the North Atlantic and North Pacific Continental polar air masses – form over the interior of Canada and Alaska

Arctic Air Masses Form over regions north of 60 latitude in Siberia and the Arctic Basin During part of the winter these areas receive almost no solar radiation and become extremely cold!

Air Mass Modification Air masses move and as they move they transfer thermal energy. As energy is transferred, the air masses characteristics change as they exchange thermal energy and moisture with the area they travel over.

Air Mass Characteristics Air Mass Type Weather Map Symbol Source Region Winter Characteristics Summer Characteristics Arctic A Siberia, Arctic Basin Bitter cold, dry Cold, dry Continental polar cP Interiors of Canada and Alaska Very cold, dry Continental tropical cT Southwest US, Mexico Warm, dry Hot, dry Maritime polar mP North Pacific Mild, humid North Atlantic Cold, humid Maritime tropical mT Gulf of Mexico, Caribbean Sea, tropical and subtropical Atlantic and Pacific Ocean Warm, humid Hot, humid