Air Pressure and Wind

These flashcards cover key concepts related to air pressure and wind, including definitions and explanations of meteorological terms and phenomena.

Barometer

An instrument used to measure atmospheric pressure.

Pressure gradient

The rate at which atmospheric pressure changes horizontally or vertically across a given distance.

Isobars

Lines drawn on weather maps that connect points of equal atmospheric pressure.

Pressure gradient force

The driving mechanism that causes air to move from regions of high pressure toward regions of low pressure.

Geostrophic wind

A theoretical wind that results from a balance between the pressure gradient force and the Coriolis effect.

Jet Stream

Fast, narrow currents of air found at high altitudes that influence weather systems.

Cyclone

A low-pressure system where air converges and rises, often leading to stormy weather.

Convergence

Occurs when air flows inward toward a central low-pressure area, forcing it to rise.

Counterclockwise rotation

The direction of wind circulation around low-pressure systems in the Northern Hemisphere.

Anticyclone

A high-pressure system where air diverges and sinks, leading to clear skies.

Divergence

Occurs when air moves outward from a central high-pressure area.

Clockwise rotation

The flow of air around high-pressure systems in the Northern Hemisphere.

Subsiding air

Air that sinks due to high pressure, leading to clear, stable weather.

Monsoon

A seasonal wind pattern characterized by a shift in wind direction, bringing wet and dry seasons.

Mid-latitude cyclone

A large-scale low-pressure system that forms along weather fronts in the mid-latitudes.

Westerlies

Prevailing winds that blow from the west toward the east between 30° and 60° latitude.

Prevailing winds

The dominant wind patterns in a region, determined by global circulation cells.

Differences between high and low pressure

High-pressure systems feature stable weather, while low-pressure systems involve cloud formation.

Average atmospheric pressure at sea level

Approximately 1013.2 millibars or 29.92 inches of mercury.

Air pressure measurement

Measured with barometers, changes with altitude, temperature, and humidity.

Surface vs upper-level winds

Surface winds are slowed by friction; upper-level winds flow parallel to isobars.

Geostrophic winds and jet streams

Geostrophic winds are balanced by pressure gradient and Coriolis forces; jet streams steer weather.

Pressure ridges and troughs

Ridges represent high pressure; troughs indicate low pressure and potential storm development.

Cyclones vs Anticyclones

Cyclones involve low pressure with inward airflow; anticyclones involve high pressure with outward airflow.

Coriolis effect

An effect that causes rotating air flow to curve and creates distinct global wind belts.

Large scale planetary circulation cells

Hadley, Ferrel, and Polar cells redistribute heat and moisture globally.

Mid-latitude prevailing winds

Westerlies that dominate and move weather systems eastward in mid-latitudes.

Types of local winds

Include land and sea breezes, mountain and valley breezes, driven by temperature contrasts.

How wind is measured

Using anemometers for speed and wind vanes for direction; also automated stations.

El Nino vs La Nina events

El Niño warms Pacific waters disrupting trade winds; La Niña cools waters strengthening trade winds.

How circulation affects precipitation

Atmospheric circulation influences where air rises or sinks, affecting cloud formation and rain.