Chapter 11 Atmosphere

Chapter 11Targets   I can explain the importance of five atmospheric gases and relate them to past studies. I can explain real-world examples that demonstrate radiation, conduction, and convection.

I can use properties of the atmosphere to explain the phenomena of thermal inversions, wind, and relative humidity. I can use the results of an experiment to make meaningful interpretation relating to the heating and cooling of the atmosphere.

I can describe two processes that lead to the formation of clouds.

Anticipation Guide

Ninety nine percent of the earth’s atmosphere is composed of nitrogen and oxygen.

Conduction currents are primarily responsible for transferring thermal energy throughout the atmosphere.

Typically warm air is less dense than cooler air.

Winds above earth’s surface tend to be greater than the speed of wind at earth’s surface.

Condensation of water vapor can release large amounts of energy that can energize major storms.

Water droplets in clouds can only form if there is some type of solid particle in the air for it to form around.

Vertical clouds are most likely to produce violent storms.

Air exerts pressure on the areas below it.

Air Pressure The pressure of the atmosphere on the surface of Earth At sea level this averages 14.7 lbs per square inch! Ruler paper / newspaper activity

Measuring Air Pressure Often measured by a barometer - thus the term “barometric pressure”. Rising or falling barometric air pressures create weather changes.

Air Pressure data Air pressure is measured in inches of mercury level on a barometer. Examples: “The mercury is at 29 inches and falling” Or….

Or… measured in millibars (mb) Average reading at sea level is about 1000 mb. “Baro” “meter” Weight - measure

The larger the number, the higher the surface air pressure Storm moving across Bering Sea towards Alaska

HIGH L0W

“Wind” develops when… Pressure differences flow to equalize. The larger the pressure difference, the higher the speed of the wind. 1030 949 Balloon demo

High and low pressure systems in Alaska area Where are the most intense winds? Why? What direction will they blow?

Wind

Thermal Inversions

Remember, by conduction, the troposphere is normally warmest were air molecules collide with earth’s surface. Thermal inversions exist when warmer air above traps cooler air below.

During rapid cooling of land, lower layers of the atmosphere lose heat to the earth’s surface (conduction) and the lower layer of the atmosphere becomes cooler than the upper layers.

Mountainous areas are prone to the development of thermal inversions Mountainous areas are prone to the development of thermal inversions. Why do you think this is? Large bodies of water can also influence the formation of thermal inversions. How might water impact this?

Thermal inversions trap pollution and prevent it from escaping Thermal inversions trap pollution and prevent it from escaping. If it persists for a few days air quality can quickly deteriorate and lead to respiratory problems for some.

Low and High pressure Which volume exerts more surface pressure? Why do you think this? What factor might cause these pressure differences? Uneven heating at surface. B A Sinking air Rising air