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30 Cards in this Set
- Front
- Back
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Why does air pressure decrease with
height more rapidly in cold air than in warm air? |
A shorter column of cold air can exert the same pressure as a taller column of warm air.
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What is considered standard sea-level
atmospheric pressure in millibars (mb) and inches of mercury (“Hg)? |
1013.25 mb and 29.92
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Height in feet above sea level of 200mb
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40,000ft
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Height in feet above sea level of 300mb
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30,000ft
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Height in feet above sea level of 500mb
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18,000ft
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Height in feet above sea level of 750mb
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10,000ft
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Height in feet above sea level of 800mb
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5,000ft
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What is the name of the instrument used to
measure atmospheric pressure? |
A Barometer
Aneroid barometer-Most common, no fluid, air partially removed to measure external pressure through small changes by expanding or retracting Mercury Barometer-Measures pressure through air raising mercury levels. |
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How does station pressure differ from sea-
level pressure (SLP)? Can the two ever be the same? |
Station pressure is the given pressure at any given location, increasing and decreasing with change in height.
Sea-level Pressure is the adjustment to make horizontal comparisons between various locations. The two are the same when the barometer is located at sea level. |
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How do you convert station pressure to sea-
level pressure? |
Add 10mb to the station pressure for every 100 meter
change from sea-level or divide the height by 10 and add to sea level. |
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How is a surface weather map created and what features can you find on it?
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Analyzing sea level pressures reading for the area. Must create common height.
High and low pressure systems, weather fronts. |
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On an upper-level chart, what is the
relationship between air temperature within a column and the height of a constant pressure surface? |
high heights - warmer temps
lower heights - colder temps |
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What is the difference between a trough and
a ridge on a constant pressure chart? |
Troughs- low pressure, cold air
Ridge- High pressure, warm air |
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How do winds move around troughs and
ridges in the mid and upper-levels of the atmosphere in the northern hemisphere? |
Trough-Winds move Counter-Clockwise (Cyclonic flow)
Ridge- Clockwise (Anticylonic flow) *Opposite in Southern Hemisphere* |
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What are the four forces that affect the
horizontal movement of air? |
1. Pressure gradient force
2. Coriolis force 3. Centripetal force 4. Friction |
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What is the force that initially sets the air
in motion? |
Pressure gradient force.
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How is horizontal pressure gradient
calculated between two locations? |
Difference in Pressure over distance
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How do you determine when the surface
winds are the strongest? |
If pressure is higher
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What does the Coriolis force do to moving
air? |
Influences directions. Right in the northern hemisphere and Left in Southern.
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How does rotation of the earth affect the Coriolis affect(Ω)?
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No rotation, no wind
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How does the Coriolis affect wind (V)?
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Greater wind speed, greater Coriolis force
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How does the Coriolis affect Latitude (Φ)?
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Coriolis force is zero at equator and increases
towards the poles. |
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How does a steep pressure gradient appear on a weather map?
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Closer together.
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Why do close isobars Indicate strong winds?
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Because of high horizontal pressure change over some distance.
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What is a geostrophic wind?
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When the Coriolis force balances with the Pressure Gradient and the wind no longer accelerates.
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What is a gradient wind?
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The flow around curved contours.
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Explain the effect surface friction has on
wind speed and direction. |
Friction reduces wind speeds, which in turn reduces the Coriolis affect.
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How do winds move around a surface low
and high pressure system in the northern hemisphere? |
Northern hemisphere- Counter clockwise and toward the surface.
Southern- Clockwise and outward. |
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Describe the direction of vertical air motions
above a surface low and high pressure systems. |
Low-Upward vertical motion
High-Descend vertical motion. |
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The high altitude winds called the Jet
Stream meander around the world. What is the difference between ‘Zonal’ and ‘Meridional’ flow within a Jet Stream flow pattern? |
Zonal- West to East(Latitude)
Meridional- North to South(Longitude) |
