Air Pollution, Climate Change and Ozone

Depletion

Core Case StudyBlowing in the Wind:

A Story of Connections Wind connects most

life on earth. Keeps tropics from

being unbearably hot.

Prevents rest of world from freezing.

Figure 5-1

CLIMATE: A BRIEF INTRODUCTION

Weather is a local area’s short-term physical conditions such as temperature and precipitation.

Climate is a region’s average weather conditions over a long time.Latitude and elevation help

determine climate.

Climate

Climate is the average weather conditions that occur in a place over a period of years.

The two most important factors are temperature and precipitation.

Solar Energy and Global Air Circulation:

Distributing HeatGlobal air

circulation is affected by the uneven heating of the earth’s surface by solar energy, seasonal changes in temperature and precipitation.

Figure 5-3

DefinitionAir pressure is pressure exerted by the weight of Earth’s atmosphere. At sea level it is equal to 14.69 pounds per square inch.

A barometer is used to measure atmospheric pressure.

Air Pressure

Pressure GradientChanges from

high to low. On a map there is an arrow to show this. A higher pressure gradient means stronger winds (the isobars on a weather map would be drawn closer together).

Air Pressure

CauseWind is caused by the

pressure gradient force. High pressure means more air, and low pressure means less air. The air moves from high to low, causing wind.

Wind

Coriolis EffectGlobal air

circulation is affected by the rotation of the earth on its axis.

Figure 5-4

Wind

The Coriolis Effect

Forces in the atmosphere, created by the rotation of the Earth on its axis, that deflect winds to the right in the N. Hemisphere and to the left in the S.Hemisphere.

Wind

Friction

A combination of the pressure gradient force and the coriolis effect. Friction at the Earth’s surface causes winds to turn a little. Friction runs parallel to the isobar.

Wind

Upper Level Flow

There is little friction up in the upper troposphere, driving surface features. Ex. during big thunderstorms, the wind in the upper level will tell which way the thunderstorm will move.

Wind

Cyclones(called hurricanes in the

Atlantic and typhoons in the Pacific)

Violent storms that form over warm ocean waters and can pass over coastal land.

Giant, rotating storms with winds of at least 74 mph. The most powerful ones have wind velocities greater than 155 mph.

Wind

AnticyclonesAn extensive system of

winds spiraling outward from a high-pressure center, circling clockwise in the N. Hemisphere and counter-clockwise in the S. Hemisphere.

Wind

Polar vs. TropicalThe atmosphere has three

prevailing winds. Prevailing winds that blow from the northeast near the North Pole or from the southeast near the South Pole are called polar easterlies.

Tropical winds that blow from the northeast in the N. Hemisphere or from the southeast in the S. Hemisphere are called trade winds.

Air Masses and Storms

Continental vs. Maritime

Continental fronts are generally cool and dry, whereas maritime (ocean) fronts are generally warm and moist. When these two air masses converge, the result is usually rain.

Air Masses and Storms

Convection Currents

Global air circulation is affected by the properties of air water, and land.

Figure 5-5

Convection CellsHeat and

moisture are distributed over the earth’s surface by vertical currents, which form six giant convection cells at different latitudes.

Figure 5-6

Hadley CellsWarm moist air rises at the equator. RainAs air rises, it spreads out north & south,

then cools and sinks at 30 degrees. DryThis is why most of the world’s deserts are

found at 30 degrees. These are called the horse latitudes (3o

degrees) because early settlers would get stuck here in their boats & couldn’t move. They would finally throw their horses overboard to lighten the load & get moving again.

Trade Winds blow towards equator

Circulation Patterns

Ferrell Cells

Warm air rises at about 60 degrees. Rain and sinks at around 30 degrees, dry,

both north and south.Westerlies. Predominant winds in US

Circulation Patterns

Polar CellsAir rises at about

60 degrees. Rainfloats north, and

sinks at around 90 degrees, both north and south. Dry

Easterlies

Circulation Patterns

Convection CellsOcean water transfers heat to the

atmosphere, especially near the hot equator. (Trade winds)

This creates convection cells that transport heat and water from one area to another.

The resulting convection cells circulate air, heat, and moisture both vertically and from place-to-place in the troposphere, leading to different climates & patterns of vegetation.

Circulation Patterns

Sea, Land, Valley, & Mountain Breezes

Sea - ocean-to-land breezes that occur during the day.

Land - land-to-ocean breezes that occur at night.

Valley - the wind blows from the plains into a valley between two mountains, the wind must divert into a smaller area. This causes high winds to form through the valleys.

Mountain - Cool air coming from the top of the mountain sinks down on the eastern slope, causing increased winds on the mountain.

Ocean Currents: Distributing Heat and Nutrients

Ocean currents influence climate by distributing heat from place to place and mixing and distributing nutrients.

Topography and Local Climate:

Land Matters

Interactions between land and oceans and disruptions of airflows by mountains and cities affect local climates.

Figure 5-8

Earth’s Current Climate Zones

Figure 5-2

Ocean Currents: Distributing Heat and

NutrientsGlobal warming:

Considerable scientific evidence and climate models indicate that large inputs of greenhouse gases from anthropogenic activities into the troposphere can enhance the natural greenhouse effect and change the earth’s climate in your lifetime.

Weather is the condition in the atmosphere at a given place and time.

Weather includes temperature, atmospheric pressure, precipitation, cloudiness, humidity, and wind.

Weather

Local Weather Weather is a local area’s short-term physical

conditions such as temperature and precipitation.

A weather front marks the boundary between two air-masses at different densities.

A front is about 100-200 km wide and slopes where warm and cool air masses collide.

Cold front Warm front

Warm Front - The boundary between an advancing warm air mass and the cooler one it is replacing. Because warm air is less dense than cool air, an advancing warm front will rise up over a mass of cool air.

The leading edge of an advancing air mass of cold air. Because cool air is more dense than warm air, an advancing cold front stays close to the ground and wedges underneath less dense, warmer air. A cold front produces rapidly moving, towering clouds called thunderheads.

Weather Warm & Cold Fronts

Stationary & Occluded Front

A stationary front is a transitional zone between two nearly stationary air masses of different density.

An occluded front is the air front established when a cold front occludes (prevents the passage of) a warm front.

Weather

SeasonsThe Earth’s 23.5 degree incline on its

axis remains the same as it travels around the sun. As the earth spins around the sun the seasons change.

Earth-Sun-MoonEarth’s axis has a 23.5° tilt. This tilt always faces

the same way, resulting in seasonal changes in sunlight and weather.

Solar year: the journey around the sun takes

365.2425 days.

Lunar month: the time between successive full moons is 29.5 days, but the moons orbit

around the Earth takes 27.3 days. Because the moon spins on its own axis once every 27.3

days, the same side of the moon always faces the Earth.

Earth day: the Earth spins on its axis with respect to the stars once

every 23h 56 min 4.09s (one sidereal day). The solar day, where

the sun returns to its zenith, is exactly 24 hours.

All images: NASA

Orbital Cycles Three long term cycles that the Earth goes through as it

orbits the Sun are:Axial tilt: the axis of the Earth varies from 21.5° to 24.5°.

Orbital eccentricity: Earth’s orbit varies from almost circular to elliptical.

Precession: the movement of the axes in space causes them to describe a cone.

All images: NASA

Axial Tilt The tilt of the Earth’s axis ranges between

21.5° and 24.5°. This can have severe effects on the climate.

An axis tilt of 21.5o allows more heating near

the poles leading to a less extreme temperature

gradient from pole to equator.

When tilted at 24.5o the variation between winter and summer temperatures

is much more pronounced.

Eccentricity When the Earth’s orbit is almost

circular (as it is now), both summers and winters are relatively mild.

This can trigger ice sheet build up as summer is not warm enough to melt winter snow.

All images: NASA

‣ When Earth’s orbit is more elliptical, summers (as shown here) in the northern hemisphere can be relatively cold while

winters are relatively warm. The opposite occurs in the southern

hemisphere

Precession Precession alters the orbital position of the summer and

winter solstices.Around 13,000 years ago the southern hemisphere’s summer occurred in June.

Orbital Cycles

The changes in the tilting of the Earth’s axis, combined with precession and eccentricity can cause variations in the amount of solar radiation reaching the Earth’s surface.

This can trigger the onset and recession of ice ages.

Formationof the

Atmosphere Most of the Earth’s early

atmosphere was lost due to the vigorous solar wind from the early Sun.

Continuous volcanic eruptions built a new atmosphere of:

water vapor

carbon dioxide

nitrogen

methane

The Atmosphere

The mixture of gases known as air, protects life on Earth by absorbing ultraviolet radiation and reducing temperature extremes between day and night.

The atmosphere is not static. Interactions involving the amount of sunlight, the spin of the planet and tilt of the Earth’s axis cause ever changing atmospheric conditions.

The auroras occur in the thermosphere and are caused by interactions between the Earth’s atmosphere and charged

particles streaming from the Sun.

Weather occurs in the troposphere. Gaseous water molecules held together by intermolecular forces cause the formation of

clouds.

STRUCTURE AND SCIENCE

The atmosphere consists of several layers with different temperatures, pressures, and compositions.

The Earth’s Atmosphere

STRUCTURE AND SCIENCE

The atmosphere’s innermost layer (troposphere) is made up mostly of nitrogen and oxygen, with smaller amounts of water vapor and CO2.

Ozone in the atmosphere’s second layer (stratosphere) filters out most of the sun’s UV radiation that is harmful to us and most other species.

The Atmosphere

Earth's atmosphere contains roughly:

The Earth’s atmosphere (where pressure becomes negligible) is over 140 km thick. Compared to the bulk of the planet, this is

an extremely thin barrier between the hospitable and the inhospitable.

78% nitrogen

20.95% oxygen

0.93% argon

0.038% carbon dioxide

Trace gases

1% water vapour

All images: NASA

Troposphere 75% of mass of

atmosphere 0 to 11 miles in

altitude 78% nitrogen, 21%

oxygen Location of Earth’s

weather Temperature

decreases with altitude until the next layer is reached, where there is a sudden rise in temperature

Stratosphere 11 miles to 30 miles in

altitude, calm Temperature increases with

altitude Contains 1000x the ozone of

the rest of the atmosphere; ozone forms in an equilibrium reaction when oxygen is converted to O3 by lightning and/or sunlight

99% of ultraviolet radiation (especially UV-B) is absorbed by the stratosphere

Mesosphere & Thermosphere

Mesosphere 30 to 50

miles in altitude

Temperature decreases with increasing altitude

Thermosphere 50 to 75 miles

in altitude Temperature

increases with increasing altitude

Very high temperatures

Composition of the Atmosphere

Components –Nitrogen 78%, Oxygen 21%, .93% argon, & .038% carbon

Layers – troposphere, stratosphere, mesosphere, thermosphere, exosphere (extends from 310 miles to interplanetary space)

Heat TransferConduction

Warm air holds more moisture than cold air. During conduction, heat & moisture from the ocean or land moves into the atmosphere.

Ex. cold air moving over warm water (like a lake), forming steam fog.

RadiationRadiation drives weather. Heat

from the sun warms the earth, which radiates the heat back into the atmosphere.