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Weather
L Murray
Dreary Days!
Low Pressure = Low Spirits = Bad
Weather
But, we need to start at the
beginning…
• The four spheres of Earth Systems Science
– Geosphere, Hydrosphere, Atmosphere, Biosphere
• Remember how they interact? We can’t study
one without looking at another.
• Weather is mainly an interaction between the
hydrosphere and the atmosphere.
• The atmosphere is where weather happens!
Earth’s Atmosphere
• The gaseous envelope surrounding Earth.
• Earth’s atmosphere has layers!
• Earth Science is like onions. It has layers!
Your Turn!
• It’s lab time! Graph the layers of the
atmosphere for yourself.
• Now’s the time to find an acronym to help you
remember!
– Troposphere, Stratosphere, Mesosphere,
Thermosphere
• Ten Silly Monkeys Thinking?
Earth’s Early Atmosphere
Little
Oxygen
More
CO2
The composition of Earth’s
atmosphere has changed over geologic
time.
Early photosynthetic life such as
cyanobacteria (blue-green algae)
consumed carbon dioxide and
generated oxygen.
Only after this could animal life be
possible on Earth.
Earth’s atmosphere is unique…
• In our solar system because it has substantial
(lots of) oxygen.
• 21% oxygen, 78% nitrogen, 1% trace gases
Trace
Gases
1%
Earth's Atmosphere
Oxygen
21%
Nitrogen
78%
Atmosphere of
Other Planets
• The atmosphere of Venus is mostly CO2 and is
very dense.
• The atmosphere of Mars is very thin and
mostly carbon dioxide.
Scientific Evidence for Atmospheric
Changes Over Time
Human, Geologic, & Biologic Activity
Change the Atmosphere
• Human activities have increased the CO2 content
of the atmosphere.
• Man-made chemicals (CFCs) have decreased the
ozone concentration in the upper atmosphere.
• Volcanic activity and meteorite impacts can inject
large amounts of dust and gases into the
atmosphere.
• The ability of Earth’s atmosphere to absorb and
retain heat is affected by the presence of gases
like water vapor and carbon dioxide.
– Greenhouse Effect
Your Turn!
• Make a mini poster about one way humans
have impacted the atmosphere.
• Choose a topic and make a mini-poster giving
me essential information. Get the basics here
and take time to color it at home.
– Here are your choices:
• CFCs and the Ozone layer
• CO2 levels
• Acid Rain
Density Changes
D = M/V
Energy Transfer
• Radiation-transfer of heat energy by
electromagnetic waves (light waves).
– You are warmer when standing in the sun.
• Conduction-transfer of heat from one molecule
to another in the same substance.
– Heat one side of a metal bar, the other side will get
hot eventually.
• Convection-transfer of heat through movement
of a fluid.
– Convection is the major mechanism of energy transfer
in the oceans, atmosphere, and Earth’s interior.
Convection
• Areas near the equator receive more of the
sun’s energy per unit area than areas near the
pole.
• In the atmosphere, convection moves
heat from the equator toward
the poles.
• Convection in the atmosphere is a
major cause of weather.
Convection = Weather
• The amount of energy reaching any given
point on Earth’s surface is controlled by the
angle of sunlight striking the surface and
varies with the seasons.
• Earth’s surface is much more efficiently
heated by the sun than is the atmosphere.
• Energy transfer between Earth’s surface and
the atmosphere creates weather.
Winds
• Winds are created by uneven heat distribution
at Earth’s surface.
• The Coriolis effect causes deflections of the
atmosphere due to the rotation of Earth.
Global wind patterns result from the uneven
heating of Earth by the sun and are influenced
by the Coriolis effect.
Global Wind Patterns
Your Turn!
• Use page 423 in your book to help you draw
and label global wind patterns.
– Draw the arrows showing the way the wind is
blowing.
– Label the names of the winds.
– Determine what wind pattern Virginia experiences
most. (Hint: Virginia is at a latitude of 37o N.)
– Save this. You will see it again!
Weather and Climate are Different!
• Weather describes day-to-day changes in
atmospheric conditions.
• Climate describes the typical weather patterns for
a given location over a period of many years.
• The four major factors affecting climate are
latitude, elevation, proximity to bodies of water,
and position relative to mountains.
• Both weather and climate are measurable and, to
certain extent, predictable.
Earth’s Climate Zones
Coldest average temperatures, no summer, little precipitation
Average temperatures
average precipitation
Warmest average yearly temperatures, no winter, lots of precipitation
On to Weather! - Clouds
• Air at or below dew point + presence of
condensation nuclei = clouds
• Dew Point = the temperature at which water
vapor becomes liquid water
• Then, cloud droplets can join together to form
precipitation.
Weather Maps
Cold Fronts – Warm Fronts
High Pressure vs. Low Pressure
• Wind flows from high to low pressure.
Tools to Measure Weather
• Thermometer – measures temperature
• Barometer – measures air pressure
• Psychrometer – measures relative humidity
Relative Humidity – Your Turn!
• Sling psychrometer measures relative
humidity – the amount of water vapor the air
is holding compared to how much it could
hold.
• Class Demo.
• Practice Calculating Relative Humidity.
Tornadoes
• A narrow, violent funnel-shaped column of
spiral winds that extends downward from the
cloud base toward earth.
Hurricanes
• A tropical cyclone (counterclockwise
movement of air) characterized by sustained
windes of 120 kilometers per hour (75 miles
per hour) or greater.
Just for fun!
• # of chirps in 15 seconds + 40 = Temperature
in degrees F.
• Ants crawl at a certain speed given the
temperature.