UNIT 7 Flashcards
Pressure
weight of a column of air; force/area
Barometer
measure pressure
Mercury Barometer
mercury in a column; as weight increases, there is more pressure pushing down which causes the mercury up the tube; higher up tube means higher pressure
Aneroid barometer
has a partially evacuated chamber that is sensitive to pressure changes
Concept of pressure
does not vary horizontally, but DECREASES rapidly WITH ELEVATION
-lower the pressure, the stronger the storm
Wind
movement of air relative to the surface; the movement is not spontaneous, and it moves as a response to the imbalance of forces acting on the air molecules (vertically or horizontally)
Pressure Gradient Force (PGF):
most important force for wind because it initiates wind; difference in pressure over a given distance (High to Low);The bigger the pressure difference means a faster wind
Hydrostatic equilibrium
balance between vertical pressure gradient force
Reasons for horizontal differences of pressure on Earth
Thermodynamic
temperature is going to cause pressure differences through causal continuum
causal continuum
radiation lead to temperature differences lead to density differences lead to pressure differences which ends in wind
Dynamic
flow patterns
Coriolis Force
due to the rotation of Earth; as the Earth rotates, different latitudes travel at different speeds-distance traveled over a certain time- based on circumference of that latitude
what causes APPARENT DEFLECTION of winds?
the change in rotational speed with latitude; in northern hemisphere winds will go to the right when air wants to go from High to Low ; in the southern hemisphere get deflected to left relative to motion; only matters when traveling a great distance
Function of latitude
maximized at poles and minimized at equator
Function of wind speed
faster winds are better deflected unlike slower winds that don’t get deflected
in the United States we get winds ____ aloft; make names of wind based on where they are coming from
WEST; warm equator air creates upper level high; cold polar air creates upper level low; high to low, deflected to the right
Frictional Force
drag force that slows down the movement of air molecules in contact with or close to Earth’s surface; depending on roughness of surface
What are LS upper level winds (Geostrophic winds) forces?
Pressure gradient force, Coriolis, no friction
PGF and Coriolis forces acting on the wind balance out over time
-relatively straight path and parallel to the isobars
-if wind is slow, Coriolis is small
What are LS surface level (Geostrophic winds) forces?
PGF, Coriolis, Friction
- Frictional force comes into play and disrupts the balance seen in geostrophic winds
- wind speed decreases, thus Coriolis Is reduced and winds cross isobars
Cyclones
low pressure; active weather; rising air; clockwise in southern and counterclockwise in northern
Anticyclones
high pressure; no active weather; sinking air
sea breezes
- during the day, land surface heats up quickly
- surface pressure on land falls and rises over the ocean
- at low levels, a small; PGF is directed from ocean to land
land breeze
- land surfaces heat and cool more rapidly than water bodies
- AT night, the temperatures above land drops dramatically causing the circulation to reverse
- The warmer air (lower pressure) is now located over water
- At low levels, a small PGF is directed from land to ocean
Chinook/Santa Ana Winds
-Forced passage of air across mountainous terrain (orographic uplift)
-Wrings out much of the moisture on the “Winward” side of the mountain
-Warms the air adiabatically as it descends the “lee” side of the mountain after its passage across the peak
Lee side of the mountain experiences dry and warm winds
