Transcript Slide 1

Density: Extend
• 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.
Weather and Climate
• 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.
Cloud Formation
• 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: What can you
say if this is too complicated?
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
Predicting the Weather from
ww2010.atmos.uiuc.edu
Example Scenario: Boulder, CO, a city on
the east side of the Rockies. Downslope
winds are expected.
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
Food Web: Explore
• 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: Explain
• 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: Extend
Card Games
Food Web: Evaluate
• 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
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