changing weather
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Changing Weather. From: Ck-12.org Foundation Earth Science Chapter 16 By: Robert Smith. weather in a location often depends on what type of air mass is over the location A key factor is whether the spot is beneath a front , the meeting place of two air masses - PowerPoint PPT PresentationTRANSCRIPT
Changing Weather
From: Ck-12.org Foundation Earth Science Chapter 16
By: Robert Smith
• weather in a location often depends on what type of air mass is over the location
• A key factor is whether the spot is beneath a front, the meeting place of two air masses
• characteristics of the air masses and their interactions determine whether the weather over an area is constant, or whether there are rapid changes
Air Mass
• air mass is a batch of air that has nearly the same temperature and humidity
• air mass acquires characteristics above an area of land or water known as its source region
• air mass that sits over a region for several days, or longer, it picks up the distinct temperature and humidity
Air Mass Formation
• Air masses form over a large area• Air masses form primarily in high pressure
zones, most commonly in polar and tropical regions
• Temperate zones are ordinarily too unstable for air masses to form
• air masses move across temperate zones so the middle latitudes are prone to having interesting weather
cPk
• symbol cPk is an air mass with a continental polar source region that is colder than the region it is now moving over
Air Mass Movement
• Air masses are slowly pushed along by high-level winds
• temperature and humidity of a particular location depends partly on the characteristics of the air mass that sits over it
• cold air masses tend to flow toward the equator and warm air masses tend to flow toward the poles
Fronts
• Two air masses meet at a front• the two air masses have different densities
and do not easily mix• One air mass is lifted above the other, creating
a low pressure zone• If the lifted air is moist, there will be
condensation and precipitation. • Winds are common
Four Types of Fronts
• stationary front the air masses do not move• may bring days of rain, drizzle, and fog• Winds usually blow parallel to the front, but in
opposite directions
Cold Fronts• a cold air mass takes the place of a warm air
mass, there is a cold front• squall line is a line of severe thunderstorms
that forms along a cold front. Behind the front is the cold air mass
Cold fronts vary by season
• spring and summer: The air is unstable so thunderstorms or tornadoes may form.
• spring: If the temperature gradient is high, strong winds blow.
• autumn: Strong rains fall over a large area.• winter: The cold air mass is likely to have
formed in the frigid arctic so there are frigid temperatures and heavy snows.
Warm Front
• a warm air mass slides over a cold air mass
Occluded Front
• occluded front usually forms around a low pressure system
• starts when a cold front catches up to a warm front
• air masses, in order from front to back, are cold, warm, and then cold again
• If the air mass that arrives third is colder than either of the first two air masses, that air mass slip beneath them both. This is called a cold occlusion
Images of Weather