19-1 Flashcards
what is air pressure?
force pushing on an area of Earths’ surface due to air’s weight; result of weight of a column of air pushing down on an area.
Air pressure pushing down is equal to air pressure pushing up
what is a barometer? what are the two types?
instrument used to measure air pressure. two types: mercury barometer and aneroid barometer
what is a mercury barometer?
A glass tube, open at the bottom sitting in a dish of mercury, is partially filled with mercury and has a small vacuum at the top. more air pressure = mercury rises, less air pressure = less mercury
what is an aneroid barometer?
most common and portable type; airtight metal chamber sensitive to pressure changes. When pressure increases, the thin walls push in; when it decreases, the walls bulge out. The chamber is connected to a dial by springs, and as the shape changes, the needle moves.
what is a barograph?
aneroid barometer connected to recording device; makes graph of continuous pressure over time
what causes wind and how does it move?
Air moves from high to low pressure to balance differences. solar radiation creates these pressure changes. Wind should flow straight, but friction and Earth’s rotation (Coriolis effect) change its direction.
the greater the differences in pressure what happens to the wind speed?
the greater the wind speed
what are isobars?
lines on a weather map that connect places of equal air pressure
what are pressure gradients? what do steep and less steep pressure gradients create?
pressure changes, steep pressure gradient creates greater acceleration of air, less steep causes slower acceleration.
what does spacing indicate in an isobar map?
Spacing indicates amount of pressure changes - closely space indicate steep pressure gradient (high winds), well spaced isobars indicate low wind condition.
where is wind direction always from?
from high-pressure areas to low-pressure areas, but not always at right angles to isobars due to the Coriolis effect and friction.
What is the Coriolis Effect and how does it affect air movement?
The Coriolis Effect causes air masses in the northern hemisphere to turn westward toward the equator. If you’re on the equator looking south, air seems to turn west because you’re moving east.
describe air flow in the northern hemisphere and in the southern hemisphere
In the northern hemisphere, air flows from northeast to southeast (clockwise), while in the southern hemisphere, it flows from southeast to northeast (counterclockwise).
how does friction influence wind direction and movement? What happens to the pressure gradient above the friction layer?
Friction slows down air movement, altering wind direction. Above the friction layer, the pressure gradient causes air to move toward low pressure.
how does the coriolis effect act to the presure gradient as soon as air moves and at high altitudes?
as soon as air moves the Coriolis effect acts at right angles to the pressure gradient, and at high altitudes, the pressure gradient and Coriolis effect balance, causing wind to flow parallel to isobars
what are jet streams?
most prominent features of airflow high above friction line, like fast-moving rivers of air near tropopause
How does the surface roughness affect wind movement near the Earth’s surface?
Over smooth ocean surfaces, friction is low, and airflow angle is small. Over rugged terrain, friction is higher, causing winds to move more slowly.
