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Air MassesLarge bodies of air
formed when a body of air hangs over a region and takes the temperature and humidity from that region
4 types
1. Continental polar
•cold and dry
•effects Michigan the most
• 2. Maritime polar
• cold and moist
• 3. Continental Tropic
• warm and dry
• 4. Maritime Tropic
• warm and moist
• effects Florida
FRONTSFRONTS
Boundary between two air masses
4 types:
1. cold
2. warm
3. stationary
4. occluded
COLD FRONT
• Cold air mass pushes a warm air mass
• steep slope
• brings thunderstorms or severe weather
Cumulonimbus clouds
WARM FRONT
• Warm air mass pushes a weaker cold air mass
• little temperature change
• brings steady rain
stratus clouds
STATIONARY FRONT• When two air
masses meet but cannot push each other
• steady rain for days
OCCLUDED FRONT• A cold front overtakes a warm
front
• warm air forced up rapidly
• LOW pressure
• and storms L
Causes of wind• 1. Uneven heating of the Earth
creates:2. Differences in air pressure
creates: High pressure area and low pressure
areaAll winds blow from a High pressure
to a Low pressure
Works with other things too!!
Clicker
• What caused the can to crush?
a) Increased external air pressure
b) Decreased external air pressure
c) Water vapor condensing
d) Liquid water evaporating SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...
3. CONVECTION CELLS
• Warm air rises; cool air sinks
4. CORIOLIS EFFECT• Caused by the rotation of the earth• Earth rotates on the average 750mph
– faster at the equator– Causes winds to be deflected tothe right in the – Northern Hemisphere
Coriolis Forceclockwise rotation, the deflection is to the left of
the motion of the object; in one with counter-clockwise rotation, the deflection is to the right.
WESTERLIESBlows from the west to the east
Effects the weather the most in the US
TRADE WINDS OR EASTERLIESBlow from the east toward the equator
Clicker
• Which way do winds blow?a) From high pressure to low pressure
b) East to north
c) Low pressure to high pressure
d) South to EastSMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...
Isobars- line that connect areas of equal air pressure
Instruments
1. Anemometer- measures wind speed
2. Wind Vane- measures wind direction
Isobars and relative wind speed• Close isobars=high wind
speed• Low Pressure System:
Increased cloudiness, winds, temperatures, and chance of precipitation.
• High Pressure System: Indicates clear, calm conditions with reduced chance of precipitation.
Cumulonimbus clouds-Contain heavy rain, lightning, hail and wind
-Possible tornadoes-Associated with a cold front
Two of the most important ingredients for thunderstorm formation are instability (unstable air) and moisture.
During a thunderstorm, the Earth's surface has a positive charge. Because opposites attract, the negative charge at the bottom of the thunder cloud wants to link up with the positive charge of the Earth's surface.
1. The electricity passes through the air and starts it vibrating. The vibrations cause sound.
2. The lightning is also very hot and heats up the air around it. Hot air expands and the air gets bigger very quickly, and pushes apart the air particles.
These vibrations are what you hear and call thunder
THUNDERSTORM DOWNBURST
Form at the base of a cumulonimbus cloud The formation of tornadoes is the result of
warm, moist air meeting cooler, dry air, and creating instability in the atmosphere.
Season: spring to mid-summer
Strongest wind speeds
Ranked on the (Enhanced) Fujita Scale
FUJITA SCALE
EF-0
EF-1
EF-2
65-85 mph
86-110 mph
111-135 mph
EF-3
EF-4
136-165 mph
166-200 mph
EF-5 Over 200 mph
Cyclone over warm water Pre-existing storm Has an eye – low pressure in the center
Has a storm surge- Most dangerous part of a hurricane Wall of water near the eye Causes most destruction and loss of life
ANDREW-1992
Hurricane season June 1- Nov.30 Tropical Depression Wind speeds
between 20 and 34 knots (23-39 mi/hr)
Tropical Storm Wind speeds between 35 and 64 knots (40-73 mi/hr)
Hurricane Wind speed greater than 64 knots (74 mi/hr)
Rotation : Clockwise or Counter clockwise ?
Counter clockwise
The eye is the center of the storm. The eye wall surrounds the eye. The
strongest winds and heaviest rains are found in the eye wall.
Rain bands are long, arching bands of clouds and thunderstorms that spiral out from the eye wall.
Hurricane season June 1- Nov.30
if it moves over land, thus depriving it of the warm water it needs to power itself, quickly losing strength.
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