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
• 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
Layers of the Atmosphere
Layers of the Atmosphere
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
Aurora borealis
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)
Three Prevailing Winds
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
Gyres
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
Warm Front
Warm Front
Warm Front
Cold Front
• Leading edge of an advancing mass of cold air
• Wedges underneath (more dense) the warmer air mass
• Produces thunderstorms
Cold Front
Cold Front
Cold Front
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
High Pressure/Low Pressure
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
Tornado
Hurricane/Typhoon
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
Uneven heating of the earth’s surface
Uneven heating of the earth’s surface
Seasonal Changes
• The earth is tilted, sometimes toward the sun (our summer) and other times tilted away from the sun (our winter)
Seasonal Changes
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
Coriolis Effect
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
El Nińo-Southern Oscillation (ENSO)
• Prevailing westerly winds weaken or cease• Surface water along the S. and N. American
coasts becomes warmer• Supresses upwellings(colder, more oxygenated
water that cycle nutrients)• Productivity decreases, sharp decline in some
fish populations• Can trigger extreme weather changes (mild
winters on east coast, stronger storms in the west)
La Nińa
• Cooling of ocean surface water• Increased Atlantic hurricanes• Colder winters here and Canada• Warmer, drier winters in southern US• Wetter winters in Pacific NW• Torrential rains in SE Asia• Lower wheat yields in Argentina• More wildfires in Florida
El Nińo-Southern Oscillation/ La Nińa
Air Composition
• Greenhouse gases trap wavelengths of infrared radiation (heat), warming the earth– Water vapor– Carbon dioxide– Methane– Nitrous oxide– Synthetic CFC’s (chloroflourocarbons )
Greenhouse Effect
Ozone Layer
• Located in Stratosphere
• O2 is continuously converted into O3 (ozone) by uv radiation
• Keeps 95% of harmful uv rays from reaching the earth
• Provides a thermal cap so warm, churning gases do not leave the troposphere
Ozone Layer
Microclimates
• Local climatic conditions
• Caused by:– Mountains– Cities– Land to ocean interactions
Microclimates-Mountains
• (Seattle) Moist air blowing inland from the ocean is forced to rise up over the mountains
• Rising air expands, cools, and condenses (RECC) so precipitation occurs
• As the drier air mass flows down the other side of the mountain it draws moisture from plants and soil
• Rain Shadow Effect-the term for the low precipitation and semi-arid conditions on the leeward side of mountains
Rise, Expand, Cool, Condense
Microclimates-Mountains
Microclimates-Mountains
Microclimates-Cities
• Concrete, asphalt, brick, and building materials absorb and hold heat and block wind flow
• Haze and smog from pollutants released from vehicles create higher temps.
Microclimates-Cities
Microclimates-Land-Ocean Interactions
• Ocean to land breezes during the day (sea breezes)
• Land to ocean breezes at night (land breezes)
Sea Breeze
Land Breeze