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