Atmospheric Pressure and Wind Flashcards

Questions and Answers

What happens to atmospheric pressure as altitude increases?

Pressure decreases with increasing altitude.

Explain how atmospheric pressure is related to air density and air temperature.

There is more pressure when gas is denser.

What causes a thermal high near the surface? A thermal low?

Thermal highs come from cold surface temperatures and thermal lows from warm surface temperatures.

What causes a dynamic high near the surface? A dynamic low?

A dynamic high happens with strongly descending air; a dynamic low is caused by strongly rising air. Signup and view all the answers

Define the following terms: barometer, millibar, isobar.

A barometer measures atmospheric pressure; a millibar is a unit of pressure; an isobar is an isoline of equal pressure. Signup and view all the answers

What is meant by a pressure gradient?

The pressure gradient is the horizontal rate of pressure change. Signup and view all the answers

What three factors influence the direction of wind?

The Coriolis effect, the pressure gradient, and surface friction. Signup and view all the answers

How and why are friction layer (surface) winds different from upper-atmosphere geostrophic winds?

Friction layer winds are disrupted by the earth's surface; geostrophic winds flow parallel to the isobars. Signup and view all the answers

Describe the relationship between the 'steepness' of a pressure gradient and the speed of the wind.

The steeper the pressure gradient, the greater the wind speed. Signup and view all the answers

What is a cyclone?

A cyclone is a system of winds rotating inward to an area of low atmospheric pressure. Signup and view all the answers

What is an anticyclone?

An anticyclone is a weather system with high atmospheric pressure at its center. Signup and view all the answers

What are Hadley Cells?

Hadley Cells are large-scale atmospheric convection cells where air rises at the equator and sinks at medium latitudes. Signup and view all the answers

Describe global wind patterns.

Winds are named by the direction from which they blow, encircled by six major wind belts. Signup and view all the answers

What are the Polar Easterlies?

The Polar Easterlies blow from the east and north at latitudes 60-90 degrees. Signup and view all the answers

What are the Prevailing Westerlies?

The Prevailing Westerlies blow from the west at latitudes 30-60 degrees. Signup and view all the answers

What are the Horse Latitudes?

Horse Latitudes are regions of high pressure where the Westerlies meet the trade winds at about 30 degrees. Signup and view all the answers

What are the Trade Winds?

The Trade Winds blow from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. Signup and view all the answers

Study Notes

Atmospheric Pressure and Wind

Atmospheric pressure decreases with increasing altitude, as there are fewer air molecules above a surface at higher elevations.
Greater air density results in higher atmospheric pressure, with more molecule movement generating heat (higher temperatures).

Thermal and Dynamic Pressure Systems

Thermal highs are caused by cold surface temperatures, while thermal lows result from warm surface temperatures.
Dynamic highs occur with strongly descending air, whereas dynamic lows form through strongly rising air.

Pressure Measurement and Definitions

A barometer is an instrument for measuring atmospheric pressure.
Millibar is a unit expressing force per surface area, while isobars are lines connecting areas of equal pressure.

Pressure Features

A "high" refers to higher pressure relative to surrounding areas, while a "low" indicates lower pressure.
A ridge represents an elongated area of high pressure; a trough denotes an elongated low pressure area.

Wind Dynamics

The pressure gradient measures the horizontal rate of pressure change, influencing wind direction.
Wind is affected by the Coriolis effect, pressure gradients, and surface friction.
Friction layer winds interface with the earth's surface, whereas upper-atmosphere geostrophic winds flow parallel to isobars unaffected by surface friction.

Pressure Gradient and Wind Speed

A steeper pressure gradient leads to higher wind speeds due to rapid air acceleration, while a gentle gradient results in slower winds.

Cyclones and Anticyclones

Cyclones are systems where winds rotate inward to a low-pressure area, with counterclockwise circulation in the northern hemisphere and clockwise in the southern hemisphere.
Anticyclones feature high-pressure centers, with air circulating slowly and associated with calm and pleasant weather.

Hadley Cells

Hadley Cells are large-scale convection systems where air rises at the equator and sinks at about 30° latitude north or south.

Global Wind Patterns

Winds are named for their originating direction and there are six major wind belts: polar easterlies, westerlies, and trade winds in each hemisphere.
These belts shift north in summer and south in winter, each covering about 30 degrees of latitude.

Specific Wind Belts

Polar Easterlies: Blow irregularly from the east and north at 60-90 degrees latitude; the polar front distinguishes them from westerlies.
Prevailing Westerlies: Found at 30-60 degrees latitude, blowing from the west and moving weather patterns across the U.S. from west to east.
Horse Latitudes: Occur at about 30 degrees, where westerlies and trade winds meet, characterized by high pressure, dry air, and variable winds.

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Description

Explore essential concepts about atmospheric pressure and its relationship with altitude. This quiz focuses on key definitions and explanations that clarify how changes in altitude affect air pressure. Perfect for students looking to deepen their understanding of meteorological principles.