Lecture 8 Air Pressure and Global Wind Flashcards
The molecules that constitute air create ______.
air pressure
True or False: Therefore, warmer air is less dense, or lighter, than colder air, and exerts less pressure.
TRue
True or False: Moist air is lighter because the molecular weight of water is less than that of the molecules making up dry air.
True
humid air is associated with ______ pressure and cold, dry air is associated with ______ pressure.
low, high
Any instrument that measures air pressure is a ______.
barometer
______ is generally the horizontal motion of air across Earth’s surface.
wind
An ______ measures wind speed in kilometres per hour
anemometer
What are the four forces that determine both speed and direction of winds?
gravitational force
pressure gradient force
Coriolis force
Centrifugal force
The _______force counteracts the outward ______ force acting on Earth’s spinning surface and atmosphere.
gravitational, centrifugal
______ drives air from areas of higher barometric pressure (more-dense air) to areas of lower barometric pressure (less-dense air), thereby causing winds
pressure gradient force
True or False: cold, dry, dense air at the poles exerts greater pressure than warm, humid, less-dense air along the equator.
True
An ______ is an isoline plotted on a weather map to connect points of equal pressure
isobar
The ______ is a deflective force that makes wind travelling in a straight path appear to be deflected in relation to Earth’s rotating surface
coriolis force
Because Earth rotates eastward, such objects appear to curve to the ______ in the Northern Hemisphere and to the ______ in the Southern Hemisphere.
right, left
In the boundary layer, ______ drags on the wind as it moves across Earth’s surfaces but decreases with height above the surface.
friction force
Pressure gradient + coriolis forces move air from _______ (anticyclone) to ______ (cyclone) from high to low pressure in Northern hemisphere and move air from _______ (anticyclone) to ______ (cyclone) from high to low pressure in Southern hemisphere
clockwise, counter clockwise
counter clockwise, clockwise
winds that do not flow directly from high to low but flow around the pressure areas, remaining parallel to the isobars are ______
geostrophic winds
surface winds spiralling clockwise out of the high-pressure area toward the low pressure are _______, where winds spiral counterclockwise into the low _______
Diverging, and converging
When geostrophic winds approach the surface, they are slowed by friction and are called ______.
surface winds
True or False: Surface winds cross isobars at oblique angles due to the increase in frictional force near
the surface.
True
True or False: Surface winds are influenced by surface roughness
True
WHat are the 4 pressure belts
Polar high
Thermal 90° N, 90° S Cold/dry
Subpolar low
Dynamic 60° N, 60° S Cool/wet
Subtropical high
Dynamic 20°–35° N, 20°–35° S
Hot/dry
Equatorial low
Thermal 10° N to 10° S Warm/wet
The winds converging at the equatorial low are known generally as the ______.
Trade winds
The ______ diminish somewhat in summer and are stronger in winter in both hemispheres.
westerlies
They descend and diverge clockwise in the Northern Hemisphere (counterclockwise in the Southern Hemisphere) and form weak, variable winds of the polar ______.
easterlies
Surface air diverging within the subtropical high-pressure cells generates Earth’s principal surface winds: the trade winds that flow toward the equator, and the ______.
Westerlies
Consider a thick column of air in the atmosphere, if that air cools:
- it contracts
- its density increases
- and the local air pressure increases
if the air warms:
- it expands
- its density decreases
- and the local air pressure falls
