SCIENCE 10: WEATHER
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Transcript of SCIENCE 10: WEATHER
SCIENCE 10: WEATHER
Air masses, high and low pressure sysems, warm and cold fronts
Air is usually in motion(Convection and the Coriolis effect)
BUTLarge portions of air
often remain in nearly the same place long enough to take on the temperature and moisture
characteristics of the land or ocean below
• Air masses can interact as they move and even collide, and when they do….
• We get weather!• The zone b/w interacting air masses
is called a front• Eventually moves due to worldwide
wind currents
Cold Fronts
• We said rain often occurs with cold fronts…why?
• Warm air is pushed up by cold air and condenses
• If the cold front is fast moving intense thunderstorms may develop sometimes bringing hail and tornadoes
Cold Fronts
Warm Front• Warm air mass overtakes a cooler
one• Warm air gently rides up over the
trailing end of the cold air mass• Precipitation may last longer than
with a cold front• Once it passes, the air is left warmer
than before the front arrived
Warm Fronts
Stationary Fronts
• Two air masses (warm/cold) in contact but neither is moving
• Some warm air rises and condenses creating stratus clouds and often rain
• The front may remain this way for several days
• = dreary, gloomy sky
Occluded Fronts
• A faster moving cold front catches up to a slower moving warm front
• All the warm air is pushed up, away from the ground, contacting the leading cold air mass
• Many types of clouds are present, one after another
• Often cause a period of steady precipitation
High Pressure Systems
• Air descends into a region, which puts more pressure on that region.
• An air mass cooled by conduction and convection when it forms over cold ground becomes more dense and settles lower to the ground
• Creates more pressure, continues to settle, draws more air from above
High Pressure Systems• Air is also pushed out toward low
pressure areas at the perimeter in all directions
• This air curves to the right due to the Coriolis Effect
• High pressure systems create a clear sky (since air is descending not rising)
• May be 100’s of kms across
Low Pressure Systems
1. Very intense heating of the ground heats air above it (conduction) Air rises, pulling more, less dense air
in beneath itAir curves to the right (Coriolis
Effect) so rising air rotates
Low Pressure Systems
2. Warm air rises in a frontal system creating low pressure systems Generally smaller than high pressure
systemsLikely to occur b/w air massesBring unstable weather conditions
(cause precipitation and often storms)
• Why do we get nice weather with high pressure systems and storms and rain happen with low pressure systems?
Wind
• Let’s hear it from Bill• If time, let’s review weather office website to
see what the high and low pressure systems can look like!