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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 AtmosphereLittle 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
Oxygen21%
Nitrogen78%
Trace Gases1%
Earth's Atmosphere
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
Ice Cores
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 ZonesColdest average temperatures, no summer, little precipitation
Average temperaturesaverage 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.
