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
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.