There are many types of weather phenomena, including events such as El Nino and common occurrences such as wind, rain and snow. The different types of weather develop because of the Earth's various air masses and fronts.
The various types of weather relate to the Earth's climate, which is generally defined as average weather and includes temperature, precipitation and the processes that produce change in them. However, weather changes develop because of the primary air masses and their movements around the planet. Air masses are identified by four primary types:
- Cold, dry
- Cold, moist
- Warm, dry
- Warm, moist
Cold and dry masses originate over polar land areas, while cold and moist masses originate over water and in polar regions. Similarly, warm and dry masses originate over tropical land areas, while warm and moist masses originate over water and in tropical regions. Once air masses form, they move to other places and cause weather changes. Seasonal shifts in air masses cause mild summers or dangerously cold winters.
Many types of weather, such as El Nino, La Nina, Arctic Oscillations and the Pineapple Express, result from the movement of air masses. As air masses move, they collide to create fronts.
Cold fronts occur when a cold air mass moves in to replace a warm one; the phenomenon often produces thunder storms. When a warm air mass replaces a cold one, a warm front occurs and rains often results. Stationary fronts occur when two masses meet but are not moving. Occluded fronts occur when the cooler air in two systems meet.