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# Atmospheric Pressure Systems

In this quiz we explore some basic principles of meteorology—the study of the phenomena of the atmosphere.

What does it mean for a high or low pressure to be headed our way, and how do they come about? In the course of answering these questions, we'll learn about the formation of atmospheric pressure systems and the dynamics they bring about.

Storm system for the infamous Hurricane Sandy.

## Atmospheric Pressure Systems

### Out in Nature

# Atmospheric Pressure Systems

Does wind blow from low pressure to high pressure areas or the other way around?

## Atmospheric Pressure Systems

### Out in Nature

# Atmospheric Pressure Systems

High air pressure zones can result from the excess weight of high density pockets, but also from the downward movement of columns of air.

Likewise low pressure zones can develop due to local drops in the density of air or from the bulk movement of air out from a zone, leaving a vacuum of sorts in its wake.

Whenever circumstances are such that these local movements (or density separations) can occur, we can expect high and low pressure systems to form and interact with each other.

## Atmospheric Pressure Systems

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# Atmospheric Pressure Systems

Which would exert lower pressure at Earth's surface: a warm air system or a cold one?

## Atmospheric Pressure Systems

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# Atmospheric Pressure Systems

Is moist air likely to exert a higher or lower pressure than dry air of the same temperature?

Hint: water molecules are lighter than oxygen molecules.

## Atmospheric Pressure Systems

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# Atmospheric Pressure Systems

The heat capacity of a substance tells us how much heat energy it takes to increase the temperature of a substance.

We can express this as $C = \frac{\Delta Q}{\Delta T}$ where $$C$$ is the specific heat, $$\Delta Q$$ is the amount of heat added, and $$\Delta T$$ is its change in temperature.

Importantly, water has a much higher heat capacity than dry soil $$C_\textrm{water} \gt C_\textrm{soil},$$ so dry land will heat up or cool off more quickly than the sea.

## Atmospheric Pressure Systems

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# Atmospheric Pressure Systems

Consider daytime sea breezes at a forest by the coast. Are these winds more likely to blow from the forest toward the ocean or from the ocean toward the forest?

Hint: the heat capacity of the ocean is higher than that of land.

## Atmospheric Pressure Systems

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# Atmospheric Pressure Systems

Is the center of a tropical cyclone (i.e. a hurricane or typhoon) a high pressure or low pressure system?

Hint: does wind blow toward the center or away from it?

## Atmospheric Pressure Systems

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# Atmospheric Pressure Systems

In this set we learned the basic principles of the formation and interaction of pressure systems. In particular, the temperature and water content of air strongly affects where it settles in the atmosphere. The movement associated with this settling can give rise to high and low pressure zones as air rushes into or out of a location. In addition, these pressure systems can interact with each other, and the land or ocean to give rise to common phenomena like sea breezes or hurricanes. These are but a small part of the larger body of fluid mechanics and thermodynamics that govern the behavior of Earth's weather.

## Atmospheric Pressure Systems

### Out in Nature

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