Chapter 8 Air Pressure and Winds pt 1 Flashcards
how do we make air pressure change at the surface?
cool column=more dense=column shrinks
warm column=molecules spread apart=column expands
surface pressure does not change, but at certain points aloft the warm column is at a higher pressure than the cold column
what is a pressure gradient force?
when the pressure of columns is different aloft. air then moves from high to low pressure, sets air in motion causing wind.
what are the steps of pressure change?
- pressure gradient aloft
- air aloft moves H→L
-cold SP↑, hot SP↓
3.pressure gradient at surface
4.air at surface moves H→L
does a column of cold air have the same surface pressure as a column of warm air?
if they have the same number of air molecules, yes.
it takes a shorter column of dense cold air to exert the same pressure as a taller column of less dense warm air
what is wind?
at surface, a horizontal difference in temperature=horizontal difference in pressure=molecules set in motion
what is a barometer?
an instrument that measures pressure in “bars” or millibars (mb)
what is barometric pressure?
atmospheric pressure
how does a mercury barometer work?
height of column of mercury (in) is a measure of atmospheric pressure
how does an aneroid barometer work?
change in external pressure cause aneroid cell inside to expand and contract
what is station pressure?
the pressure you measure directly where you are, ACTUAL PRESSURE
what is sea-level pressure?
pressure readings when they are corrected for altitude. adjusted to ‘mean sea level’
how do we correct altitude?
add 10 mb for every 100m above sea level
what are isobars?
lines connecting points of equal pressure
what is a pressure gradient?
magnitude of the change in pressure between two points divided by the distance between the two points.
-closer together the isobars, the steeper the gradient, the FASTER the winds
what are isobaric maps?
show height variations along constant pressure
