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Atmosphere And Climate. Atmosphere. Invisible layer of gases that surround the earth 78% nitrogen 21% oxygen 1% argon, carbon dioxide, neon, helium, water vapor, air pollutants Atmosphere becomes less dense as you move upwards into space. Atmosphere Origin.
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Atmosphere • Invisible layer of gases that surround the earth • 78% nitrogen • 21% oxygen • 1% argon, carbon dioxide, neon, helium, water vapor, air pollutants • Atmosphere becomes less dense as you move upwards into space
Atmosphere Origin • Gases were released from the planet itself • Functions: • Protects earth from uv rays, x-rays, cosmic rays • Allows visible light and infrared (heat) to penetrate, warming the earth • 2.3-2.7 billion years ago evolution of photosynthetic organisms
Layers of the Atmosphere • Troposphere • Stratosphere • Mesosphere • Thermosphere • Exosphere • Memory technique: Troy smiled more than Ed
Troposphere • Closest to the surface of the earth, extends about 6.2 miles up • Temp. decreases with increasing altitude • Weather occurs in this layer
Stratosphere • Extends 6.2-28 miles up • Uniform temperature • Jets fly here • **contains ozone layer**
Mesosphere • 28-50 miles • Lowest temperature in atmosphere (-138oC)
Thermosphere • 50-310 miles • Temp. rises steadily with increasing altitude • Gases absorb x-rays and short wave uv radiation • Aurora borealis occurs here
Exosphere • 310 miles to space
Atmospheric Dynamics • Atmospheric circulation • Transfers heat from equator to the poles (warm air near equator rises, then cools and sinks again) • Moderates earth’s temperature • The atmosphere circulation AND the ocean currents determine climate • Climate=avg. temp. and avg. precipitation
Surface Winds • Connects the earth; carrying heat, moisture, plant nutrients, and long-lived pollution • Winds are complex horizontal movement of the atmosphere • Are the result of differences in atmospheric pressure and the earth’s rotation
Differences in Atmospheric Pressure • Winds blow from high pressure to low pressure (the greater the difference between the high and low, the stronger the wind
Earth’s Rotation • Earth rotates from west to east • Coriolis Effect: earth’s rotation causes the winds to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere
Three Prevailing Winds • Winds are named for the direction they come FROM • Polar easterlies (north and south poles) • Westerlies (mid-latitudes) • Trade winds (tropics)
The Ocean • Salt water covers ¾ of the earth’s surface (continuous body of water, but divided into 4 sections-Pacific, Atlantic, Indian, Arctic) • Pacific covers 1/3 of earth and contains more than ½ of earth’s water
Ocean Currents • Caused by prevailing winds • Gyres: circular ocean currents • Influenced by Coriolis Effect • Varying density-warm water is less dense than cold water
Weather • Short term properties of the troposphere such as: • Temperature • Pressure • Humidity • Precipitation • Cloud cover • Wind direction and speed
Fronts • Boundary between 2 air masses with different temps and densities • Warm front • Cold front
Warm Front • Boundary between an advancing warm air mass and the cooler one it’s replacing • Warm air is less dense, so it rises up over the mass of cooler air • First signs: high, wispy clouds • A moist warm front can bring days of cloudy skies and drizzle
Cold Front • Leading edge of an advancing mass of cold air • Wedges underneath (more dense) the warmer air mass • Produces thunderstorms
Air Pressure • Caused by tiny molecules bouncing off of each other; affected by gravity • Air pressure at the earth’s surface is greatest because of the weight of all of the other air particles being pulled by gravity • High pressure • Low pressure
High Pressure • High, dry, cool • Winds are clockwise and out
Low Pressure • Low, moist warm • Winds move counterclockwise and inward
Extreme Weather • Tornados (form over land)-each year more than 800 touch down in the US • Tropical Cyclones (form over water) • Form over Atlantic Ocean=hurricanes • Form over Pacific Ocean=typhoons • The warmer the water where the storm tracks, the more energy the storm has and the more damaging it will be
Typhoons/Hurricanes • Negative Impacts-deaths, property damage • Ecological Benefits: • Flushes out excessive nutrients, dead and rotting sea grass from coastal bays and marshes. This flushing out in turn: • Reduced brown tides • Increased growth of sea grasses • Increased the number of shrimp, crabs, fish
Climate • A region’s general pattern of atmospheric or weather conditions over a long period of time (weather is more of a day to day thing) • 2 factors that determine climate: • Average temp. • Avg. precipitation
Climate • Due to air and ocean circulation • Factors that determine global air/ocean circulation: • Uneven heating of the earth’s surface • Seasonal changes • Rotation of the earth • Long term variations in amount of solar energy striking the earth • Properties of air and water
Uneven heating of the earth’s surface • At the equator it is warmest because rays are direct • At the poles it is coldest because rays hit at a low angle
Seasonal Changes • The earth is tilted, sometimes toward the sun (our summer) and other times tilted away from the sun (our winter)
Rotation of the Earth • Due to the Coriolis Effect, winds and ocean are deflected creating convection currents that transfer heat from the equator • http://www.uwf.edu/atc/projects/coriolis/main.swf
Long Term Variations in the Amount of Solar Energy Striking the Earth • Earth wobbles on its axis (22,000 year cycle) • Earth tilts more (44,000 year cycle)
Properties of Air and Water • Heat from the sun evaporates ocean water and transfers heat to the atmosphere • Convection currents circulate air, heat, and moisture • El Nińo • La Nińa • Air composition • Ozone