Transcript Atmosphere And Climate

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/ma
in.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