Chapter 6: Atmospheric Pressure and Global Circulation Patterns

Dynamic low

Strongly ascending air causing low pressure due to motion

Barometer

Instrument measuring pressure; fluid rises in high pressure and less in low pressure

Isobars

Lines of equal pressure on a map

Pressure gradient force

Wind blows from high to low pressure across isobars

Coriolis force

Force from Earth's rotation deflecting winds right in the northern hemisphere and left in the southern hemisphere

Geostrophic winds

Airflow parallel to isobars due to pressure gradient and Coriolis forces

Friction

Slows wind near the surface; decreases with height

Anticyclones

High pressure systems with descending air (good weather)

Cyclones

Low pressure systems with ascending air (clouds and bad weather)

Intertropical convergence zone (ITCZ)

Warm air rising in the tropics creating a convergence zone

Subtropical high (STH) Pressure System

Band of high air pressure at 25-30 N and S latitude with calm winds and clear skies

Westerlies

Major wind system in midlatitudes deflected by Coriolis

Jet stream

High-speed air river in the upper atmosphere

Polar easterlies

Winds flowing away from polar highs turning due to Coriolis

Monsoon

Seasonal wind reversal phenomenon

Katabatic winds

Extreme mountain breeze

Thermohaline Circulation

Slow-moving ocean current driven by water density differences

Gyres

Distinct circulatory systems in the ocean

ENSO (El Nino Southern Oscillation)

Tropical Pacific atmospheric-oceanic feature causing climate anomalies

Atmospheric Pressure

Force exerted by gas molecules on every surface the gas touches

Factors influencing air pressure

Density and temperature affect pressure; higher density and warmer temperature increase pressure

Ideal Gas Law

Relates pressure (P), temperature (T), and density (p) with the gas constant (R)

Dynamic high

Strongly descending air causing high pressure due to motion

Thermal high

Very cold surface conditions causing high pressure due to temperature

Thermal low

Very warm surface conditions causing low pressure due to temperature