Chapter 5. Atmospheric Pressure, Winds, and Circulation Patterns

Mercury Barometer

First tool used to identify and measure atmospheric pressure. Utilized mercury in a glass rod

Barometric Pressure

Another word for atmospheric pressure

Aneroid Barometer

Another device used to measure barometric pressure. Utilizes a hollow metal accordion-like cell that is sealed after air inside is removed

Standard Sea Level Pressure

1,013.2 Millibars or 29.92 in of Mercury

Altitude

Height in the air above sea level

Elevation

Height on the surface of the Earth above or below sea level

Cyclone

Low pressure system

Anticyclone

High pressure system

Convergent wind circulation

Air rises (horizontal inflow)

Divergent wind circulation

Downward motion of air (horizontal outflow)

Isobar

Lines on a map that connect locations together that are of equal air pressure

Pressure gradient

Difference in pressure on a map shown by frequency and closeness of isobars

Coriolis Effect

The deflection of air to the right in Northern Hemisphere and left in Southern Hemisphere (stronger closer you go to the poles)

Geostrophic wind

Theoretical type of wind that happens when Coriolis effect and pressure gradient becomes equal

Prevailing wind

Wind that seasonally or commonly flows from the same direction

Trough

Elongated area of low pressure

Equatorial trough/ equatorial low

Belt near the equator with low pressure and high temperatures because of the sun, located at 0 degrees latitude (Air rises)

Subtropical highs

Directly North and South of the Equatorial low, located at 30 degrees latitude, cells of high pressure dominate

Subpolar lows

Belt North and South located at around 60 degrees latitude, cells of low-pressure dominate (air rises)

Polar high

Belt located at around 70-90 degrees latitude, brings extreme cold temperatures, cold, dense air sinks, cells of high pressure are found here

Siberian high

Strong anticyclone that forms in Eastern Asia and drives cold and dry conditions

Canadian high

Strong anticyclone that forms in Canada and drives cold and dry conditions to the U.S.

Icelandic low

Low pressure system that forms in the North Pacific Ocean

Aleutian low

Low pressure system that forms in the North Pacific

Azores high/Bermuda high

High pressure system that impacts the North Atlantic Ocean, North America, and Europe

Pacific/Hawaiian high

High pressure system that impacts climates on the west coast of North America

Polar Easterlies

Winds flowing near the North pole towards the East from the West

Westerlies

Belt of winds from the west in mid latitudes in both hemispheres

Trade winds/tropical easterlies

Winds blowing from subtropical highs toward the equator

Northeast trade winds

Trade winds in Northern hemisphere

Southeast trades

Trade winds in southern hemisphere

Intertropical Convergence Zone (ITCZ)

Where trade winds from both hemispheres converge on the equatorial regioin

Doldrums/equatorial calms

Areas near the equator that experience solar heating, rising air, heavy rainfall, and calm winds with no prevailing direction

Horse latitudes

Subtropical belt of calm conditions

Polar front

Where warm air from the westerlies meets cold air from polar regions, causing air that is warm to be pushed upwards rapidly

Jet stream

Very strong air currents embedded within upper air westerlies

Polar jet stream

Faster, internal current of air within the upper air westerlies above the polar front

Subtropical jet stream

Upper air westerly that flows above subtropical highs in lower midlatitudes

Rossby Wave/long wave

A wave formed in upper air westerlies where warm air pushes North and colder air pushes South

Monsoon

Directional reversal of winds from one season to the opposite

Land breeze-sea breeze

Local wind system driven by temperature difference between land and sea

Mountain breeze-valley breeze

Local winds that occur due to the temperature difference between valleys and mountains

Chinook

Local wind in Rocky Mountains

Foehn

Local wind in the Swiss Alps

Santa Ana wind

Formed from high pressure over desert regions of southern California and Nevada. Causes heating of land during winter and fall

Katabatic/drainage winds

Occur under cold, calm, and clear conditions; local to mountain regions

Surface ocean current

Steady, continuous flows of sea water that act like rivers in the Ocean

Gyre

Major ocean current that move in broad circular patterns around subtropical highs

Upwelling

Rise of dense, cold water toward the surface

El Nino/southern oscillation (ENSO)

Seesaw pattern where a rise in pressure occurs in Eastern Pacific and causes a drop in pressure in Western Pacific

Teleconnection

Weather that can be triggered by phenomena far away

North Atlantic Oscillation (NAO)

Seesaw between pressure in Azores high and Icelandic low. (Positive NAO is higher than average pressure in Azores, Negative NAO is less pressure in Azores high)