Weather and Climate: Ch. 6 Flashcards
Instrument used to measure air pressure and monitor changes
Barometer
Most accurate and first invented type of barometer
Mercury Barometer
When was the Mercury Barometer invented?
1643
Most common type of home barometer
Aneroid (no liquid) Barometer
Rising air pressure = …
continued fair or clearing weather
Falling air pressure = …
signals approach of stormy weather
lines that connect points of equal pressure
Isobars
Isobars are _____ black lines at intervals of __ mb
solid; 4
What is isobars base value
1000 mb
Surface maps/isobars show variations in ________ along a ________ surface (sea level)
pressure; horizontal
Commonly used to study weather above surface
Upper atmosphere charts
Major weather systems travel here
500 mb (18,000’) chart
Elongated high pressure areas
Ridges
In ridges, ______ air moving _______
warm; poleward
Elongated low pressure areas
Troughs
In troughs, ______ air moving towards _________
cold; equator
What is the main cause of pressure differences and wind?
unequal heating of Earth’s surface
Winds blow from _____ to ____ pressure
high to low
What 3 forces influence winds?
- Pressure Gradient Force (PGF)
- Coriolis Effect
- Friction (only affects surface winds)
Difference in pressure over distance, directed perpendicular to isobars from high to low
Pressure Gradient Force (PGF)
Force that causes wind to blow
Pressure Gradient Force (PGF)
Pressure gradient force is big for _______
SPEED
In PGF, closely spaced isobars = …
steep pressure gradient
In PGF, widely spaced isobars = …
gentle pressure gradient
Steep pressure gradient produces _____ winds
strong
Gentle pressure gradient = ______ winds
light
Apparent deflection due to rotation of earth
The Coriolis Effect
In the Coriolis Effect, object deflect to _____ in northern hemisphere
right
In the Coriolis Effect, object deflect to _____ in southern hemisphere
left
In Coriolis Effect, stronger the wind = …
greater the deflection
Coriolis effect is strongest at _____ and weakens to ________
poles; equator
The Coriolis effect influences _________, not ______
direction; speed
The Coriolis effect only has significant impact over _____ distances
long
Frictional drag of ground slows surface winds, reducing …
Coriolis Force
Influences wind in first mile of atmosphere
Friction
Blows parallel to straight isobars at altitudes above friction layer
Geostrophic Wind
Balance between PGF and Coriolis force
Geostrophic Wind
Wind that blows parallel to curved isobars above friction layer
Gradient Wind
Gradient wind viewed above in northern hemisphere, blow _________ in anticyclones (high)
clockwise
Gradient wind viewed above in northern hemisphere, blow ____________ in cyclones (low)
counterclockwise
Friction causes winds at surface to blow at an angle across isobars from high to low pressure
Surface Winds
In surface winds, winds cross isobars at about ___
30°
In northern hemisphere, surface winds blow clockwise and …
out of high
In northern hemisphere, surface winds blow counterclockwise and …
into a low
In surface winds, in center of a high, winds are ________
diverging (descending)
In surface winds, in center of a low, winds are ________
converging (lifting)
In surface winds, ________ is frequently a stormy weather system
cyclone
To locate the center of storms, stand with your ____ to wind, center of lowest pressure will be to your _____, turn clockwise about ___ to surface wind
back; left; 30°
Wind that blows consistently from one direction more than from any other
Prevailing wind
Prevailing winds, dominate _____ _______
wind direction
Prevailing winds can …
greatly affect a climate
Winds are labeled by direction from which they blow
Wind Vane
Measures wind speed
Anemometer
Cylindrical clumps of snow often with a hole extending lengthwise
Snow Rollers
Snow Rollers are ______
rare
What is the windiest region in the US?
Central Plains
What is the average wind speed in the Central Plains?
12 mph
