Atmospheric Pressure and Weather Systems

Flashcards covering key concepts related to atmospheric pressure, pressure differentials, temperature's effect on air columns, pressure measurement, different types of pressure, and the analysis of weather using surface and upper-air maps, including cyclones and anticyclones.

How does air pressure change with height?

Air pressure decreases with height because there are physically fewer air molecules above you.

What determines air pressure at a given surface?

The amount of air molecules above that surface.

What effect does warming a column of air have on pressure aloft?

Warming a column of air leads to a higher pressure aloft.

What effect does cooling a column of air have on pressure aloft?

Cooling a column of air leads to a lower pressure aloft.

What is the Pressure Gradient Force (PGF)?

It is the difference in pressure that causes air to move from an area of high pressure to an area of low pressure.

In what direction does air naturally want to move due to pressure differentials?

Air wants to move from high pressure to low pressure.

What is the approximate standard sea level pressure?

Approximately 1013 millibars (or hectopascals).

What instrument is used to measure pressure?

A barometer.

What is 'station pressure'?

Raw pressure measurements taken at a specific location that do not account for elevation, causing them to vary significantly with altitude.

What is 'sea level pressure'?

Pressure that has been adjusted to account for elevation, effectively removing the effect of altitude to allow for fair comparisons between different locations.

What type of lines are plotted on surface maps to show areas of constant pressure?

Isobars.

What does an isobar represent?

A line connecting points of equal atmospheric pressure.

Why do meteorologists use isobaric charts (or maps of constant pressure) for upper-air analysis instead of constant altitude maps?

Because weather systems and wind primarily move on pressure surfaces (isobaric surfaces), not at constant altitudes.

What variable is typically contoured on isobaric charts (upper-air maps)?

Height (altitude) above sea level where that specific pressure level is found.

Low pressure systems on upper-air maps are often associated with which type of height pattern?

Troughs (decreasing heights of the isobaric surface).

High pressure systems on upper-air maps are often associated with which type of height pattern?

Ridges (increasing heights of the isobaric surface).

What are low pressure systems in the atmosphere called?

Cyclones (e.g., tropical cyclones, hurricanes, nor'easters).

What are high pressure systems in the atmosphere called?

Anticyclones.

In the Northern Hemisphere, in what direction does air flow around low pressure systems (cyclones)?

In a counterclockwise direction.

In the Northern Hemisphere, in what direction does air flow around high pressure systems (anticyclones)?

In a clockwise direction.

What does an isotherm represent on a weather map?

A line connecting points of equal temperature.