What is the lowest atmospheric pressure ever recorded?
870 Millibars (25.7 in.) during a Typhoon Tip
What is standard sea level pressure in millibars? In inches of mercury? In pounds per square inch?
- 2 Millibars
- 92 in.
- 69 Pounds per square in.
What force is responsible for generating wind?
Horizontal movement of air. Air flowing from areas of higher pressure to areas of lower pressure
How does a barometer work?
Uses a glass tube filled with mercury
What is an aneroid barometer?
A borometer without liquid. Uses an expanding chamber
What is a barograph?
A device that continuously records air pressure
what are the controls of wind?
Pressure gradient force, Coriolis effect, friction
What is an isobar?
a line of equal air pressure
What is a pressure gradient?
Pressure change over distance
What is the Coriolis effect?
Apparent deflection in the wind direction due to Earth’s rotation
Deflection is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere
What is friction?
Only important near the surface
Acts to slow the air’s movement
What are the two kinds of upper air winds?
Geostrophic winds, the jet stream
What are geostrophic winds?
Generally blow parallel to isobars
What is the jet stream?
“River” of air
High altitude
High velocity (120–240) kilometers per hour
Why doesn’t the Coriolis effect cause a baseball to be deflected when you are playing catch?
Over short distances, the effect is not noticeable
How does the Coriolis effect modify air movement?
Turns the air to the right in northern hemisphere, and to the left in the southern hemisphere
What is the highest wind speed ever recorded?
372 kph (231 mph)
In what prevailing winds do we reside?
The westerlies
What is a cyclone?
A center of low pressure
Pressure decreases toward the center
Associated with rising air
Often bring clouds and precipitation
What are cyclone winds like in the N. and S. Hemispheres?
In the Northern Hemisphere Inward (convergence) Counterclockwise In the Southern Hemisphere Inward (convergence) Clockwise
What is an Anticyclone?
A center of high pressure
Pressure increases toward the center
What are the winds like in an Anticyclone?
In the Northern Hemisphere Outward (divergence) Clockwise In the Southern Hemisphere Outward (divergence) Counterclockwise Associated with subsiding air Usually bring “fair” weather
What is the underlying cause of general atmospheric circulation?
Unequal surface heating
What influence do continents have on general atmospheric circulation?
Seasonal temperature differences disrupt the
Global pressure patterns
Global wind patterns
What is a monsoon?
Seasonal change in wind direction Occur over continents During warm months Air flows onto land Warm, moist air from the ocean Winter months Air flows off the land Dry, continental air
What are local winds, and what are the types of them?
Produced from temperature differences Small-scale winds Types- Land and sea breezes Mountain and valley breezes Chinook and Santa Ana winds
What are the two ways we measure wind?
Direction and speed
How do we measure wing direction, and why is that important?
With a wind vane, and because winds are labeled by their origins
How do we often measure wind speed?
With a cup anemometer
Why are changes in wind direction important?
Associated with locations of: Cyclones Anticyclones Often bring changes in: Temperature Moisture conditions
What is El Nino?
A countercurrent that flows southward along the coasts of Ecuador and Peru
Warm
Usually appears during the Christmas season
Blocks upwelling of colder, nutrient-filled water, and anchovies starve from lack of food
What is the Southern Oscillation?
When pressure changed between the eastern and western Pacific due to El Nino
What is El Nina
Opposite of El Niño
Triggered by colder-than-average surface temperatures in the eastern Pacific
Typical La Niña winter
Blows colder than normal air over the Pacific Northwest and northern Great Plains while warming much of the rest of the United States
Greater precipitation is expected in the Northwest