Earth's Protective Blanket: The Atmosphere
The atmosphere is the layer of gases surrounding the Earth. It is divided into layers based on temperature changes with altitude.
Troposphere: The lowest layer, where we live and where all weather occurs. Temperature decreases with altitude.
Stratosphere: Contains the ozone layer, which absorbs harmful UV radiation. Temperature increases with altitude due to this absorption.
Mesosphere: The layer where most meteors burn up. Temperature decreases with altitude.
Thermosphere: The outermost layer with very thin air. Temperature increases dramatically due to absorption of high-energy solar radiation. Contains the ionosphere, which is important for radio communications.
Weather vs. Climate
Weather: The state of the atmosphere at a specific time and place. It includes factors like temperature, humidity, precipitation, and wind. It is short-term and can change rapidly.
Climate: The long-term average of weather in a particular area, typically over 30 years or more. It describes the general patterns and ranges of weather conditions.
Global Wind Patterns and the Coriolis Effect
Uneven heating of the Earth (more intense at the equator) creates large convection cells in the atmosphere. However, the wind does not blow straight from the poles to the equator.
The Coriolis effect, an apparent force caused by the Earth's rotation, deflects moving objects (including air currents).
In the Northern Hemisphere, it deflects objects to the right.
In the Northern Hemisphere, it deflects objects to the left.
This effect is responsible for breaking the large convection cells into smaller ones (Hadley, Ferrel, and Polar cells) and creating the global prevailing wind patterns, like the trade winds and the westerlies.
Air Masses and Fronts
An air mass is a large body of air with relatively uniform temperature and humidity.
A front is the boundary between two different air masses. Fronts are the primary cause of significant weather events.
Cold Front: A cold, dense air mass pushes under a warmer air mass, forcing the warm air to rise rapidly. This often creates thunderstorms and sharp changes in temperature.
Warm Front: A warm, less-dense air mass slides up and over a colder air mass. This typically produces gentle, widespread precipitation and gradual warming.