• Molecules in a hotter gas move faster, all else being equal.

the kind of molecule is the same

the greater the average kinetic energy of the molecules the higher the temperature. (Recall K = mv2/2)

Density: Extend

• If a fluid is relatively free to expand (constant pressure) a warmer fluid is less dense. This is why we say things like “hot air rises” – which isn’t quite correct.

• A more dense fluid pushes a less dense fluid upward (buoyancy) and as the less dense fluid rises, it cools and becomes more dense. It then falls and pushes other less dense fluid upward. The object created by this cycle is called a convection cell.

Density: Extend

If the air is leaving a high pressure area, how does the pressure stay high?

In order for the pressure to stay high, more air must be drawn into the high pressure area from some higher altitude.

Density: Extend

If the air warms in a high pressure area, why do we get cold Arctic high pressure areas in the winter?

It's relative. If the air starts out at -25° Fahrenheit, and then warms up to 0° Fahrenheit through sinking and warming, we can conclude that warming has occurred, but it is still mighty cold and will be a high pressure area.

Density: Extend

• The equator receives more concentrated sunlight than the poles.

• The seasons result from the tilt of the Earth’s axis, not its distance from the sun.

• The jet streams move from west to east and this can cause weather systems to move from west to east.

• High pressure areas are often associated with clear skies. Low pressure systems are often associated with clouds and precipitation.

• Warm and cold air masses meet at fronts and often weather is determined by the nature of the interaction of the air masses at the fronts.

Weather and Climate

• It requires heat to evaporate and melt a substance. A substance can condense or freeze as heat is extracted.

• Humidity measures the water vapor in the air.

• Relative humidity is the percentage of the maximum amount of water vapor possible in the atmosphere under the current conditions, so it changes with the conditions.

• Large interacting masses of air that can be cooler and dryer, cooler and wetter, warmer and dryer and warmer and wetter control the large scale weather.

Weather and Climate

• Clouds can form as wet, warmer air rises and cools.

• When the temperature falls below the dew point, there is a net condensation and a cloud forms.

• Clear skies actually contain water drops that are so small you can’t see them. Water is constantly evaporating from and condensing back onto the surface of these drops. If the temperature falls to the dew point, there will be more condensation and less evaporation and larger water drops will be formed, which make the cloud. What do think happens if the temperature increases?

• It isn’t correct to say that air “holds water vapor”. All the molecules of gasses in the atmosphere are in a continual dance which is controlled by the temperature, pressure and density.

Cloud Formation

When the temperature drops below the dew point, there is a net condensation and a cloud forms.

http://www.ems.psu.edu/~fraser/Bad/BadClouds.html

Cloud Formation: What can you say if this is too complicated?

Example Scenario: Boulder, CO, a city on the east side of the Rockies. Downslope winds are expected.

Predicting the Weather from ww2010.atmos.uiuc.edu

Prediction: Unlikely. Downslope winds (or wind blowing down the mountain) tend to be very dry, warming the air as it descends, creating an unfavorable environment for the development of precipitation. Rising air in the presence of downslope winds is unlikely.

Scenario 1: A cold front is approaching from the west, but the air both ahead of and behind the front is very dry.

Prediction: Unlikely. The cold front is an important lifting mechanism, but there isn't enough moisture for precipitation to develop.

Scenario 2: A warm front is approaching and the air behind and ahead of the front is very moist.

Prediction: Likely. With moisture present and lifting forced by "overrunning" of the warm front, these are favorable conditions for precipitation to develop.

Scenario 3: Upslope winds are expected in Boulder, CO and the air has been very moist for the past couple of days.

Prediction: Likely. With moisture available, winds blowing up the mountain will provide the lifting of air (since air can't go through the mountain, it must go up and over), and this combination creates a favorable environment for the development of precipitation.

Scenario 4: The trend for the latest batch of precipitation is a steady eastward movement of 30 miles/hour. The latest position is roughly 700 miles west of here. Will precipitation arrive within 24 hours?

Prediction: Likely. Using mathematics, at 30 miles/hour the precipitation should move 720 miles over a 24 hour period, which means that it will have reached us by then (though just barely).

Food Web: Engage

Food Web: Engage

• Classify your cards into different categories that you pick.

• Once you have done it one way, come up with a new scheme.

• Find food chains with two, three, and four links.

• Be sure to take notes on your explorations.

Food Web: Explore

• producers, consumers, secondary consumers, and decomposers

• carnivores, herbivores, omnivores

• invertebrates, vertebrates

• mammals, birds, insects, arachnids, reptiles, amphibians, plants

• see Chapter 10

Food Web: Explore

• discuss any cards that didn’t fit into your classification scheme and give reasons why they were left out

• define producers, consumers and decomposers and list their properties

• define carnivores, herbivores, and omnivores and their list properties

• explain the role of the Sun in your food webs

Food Web: Explain

Card Games

Food Web: Extend

• design a shelter for a living organism

• design a habitat for a living organism

• draw a food web using the organisms and objects on the cards

Food Web: Evaluate

A cow with its tail to the west makes weather the best; a cow with its tail to the east makes weather the least.

A. true

B. false

Animals graze with their tails pointing to the wind. An easterly wind has a higher probability of bringing rain.

The higher the clouds, the better the weather.

A. true

B. false

C. questionable

High clouds may imply fair weather in the short term, but if those cirrus clouds are increasing rapidly, there is a good chance of rain in 24 hours.

If cats lick themselves, fair weather

A. true

B. false

When high pressure is drifting overhead and skies are sunny, relative humidity levels are usually low and the air is dry. Static electricity builds up on a cat’s fur making it feel unclean.

The heaviest rain falls following a full or new moon.

A. true

B. false

Although the moon is a major contributor to the tides, there is no scientific evidence that it affects the fluid atmosphere. Enjoy your picnic after the full moon.

If you count 20 seconds between seeing the flash of lightning and hearing the thunder, how many miles away is the strike?.

A. 1 mile

B. 4 miles

C. 10 miles

D. 20 miles

E. Impossible to tell.

Light travels so fast, you see the flash nearly instantly. Sound travels around 1 miles in a 5 seconds.

A. UFO

B. cirrus cloud

C. lenticularis cloud

D. cumulus cloud

E. fog