Atmospheric Composition and Structure

What is in the Atmosphere?

• The other gases include...

Neon Krypton Methane Helium Xenon Hydrogen Ozone

• The atmosphere is mostly air, which is a mixture of gases.

• There is also water vapor and small particles in the atmosphere.

Layers of the Atmosphere

Troposphere

Thermosphere

Stratosphere

Exosphere

Mesosphere

Key Facts: Troposphere• Lowest level of the atmosphere

– Experiences the highest air pressure. – Contains most of the atmosphere’s mass. – Most dense layer – Heated by the Earth through conduction.

• According to the temperature profile, as altitude increases, temperature decreases. – Allows for the creation of

convection currents.

The Troposphere is characterized by weather!

Key Facts: The Stratosphere

• According to the temperature profile, as altitude increases, temperature increases. – There is a temperature

inversion, which means warm air is on top of cold air!

– Air CANNOT rise because it is colder than its surroundings, and cold air sinks!!

Ozone Layer!

Key Facts: The Mesosphere• The mesosphere is colder because

the gases CANNOT absorb the sun’s radiation. – Continues through to the surface

where it is absorbed. – Top of this layer is somewhere

between -90°C and -100°C.

• The thermosphere contains gases that absorb the sun’s radiation. – Blocks the x-rays and some UV-

radiation. – The temperature depends on the

sun’s activity.

Factors that Affect Climate• Climate greatly affects

the species that exist in an ecosystem. – Climate is the average

weather of an area over a long period of time.

Temperature Precipitation

• Two main climate factors that influence life in an ecosystem are:

Factors that Influence Climate

Factors that Influence Climate• Unequal heating of Earth’s surface by the Sun.

• Angle of insolation, albedo, proximity to water. • Rain Shadow Effect • Atmospheric Convection Currents

Shape of the Earth

The light is more intense when it hits the Earth’s surface at higher angle.

Earth’s Tilt and Orbit Around the Sun• There are three ingredients that create the seasons

on Earth. – Earth revolves around the sun. – Earth’s axis is tilted. – Earth’s axis always points in the same direction.

• Because of this, the angle of insolation changes in a given location, which changes the: – Intensity of the insolation. – Temperature of the area.

Other Factors To Consider...• Albedo

– Some areas reflect the sun’s light better than others. • Use albedo to quantify how well it reflects.

Changes In Albedo• The concern with global warming is the melting of the

polar ice caps, glaciers, and sea ice.

Urban Heat Island Effect• The increase in

temperature of a man-made area in comparison to the area’s natural landscape.

– The annual mean air temperature of a city with 1 million people or more can be 1-3°C warmer than its surroundings.

– In the evening the difference can be as high as 12°C. • More pronounced at night because of the slow release of heat from urban

infrastructure.

Urban Heat Island Effect• The increase in temperature of a man-made area in comparison

to the area’s natural landscape. – Built surfaces replace vegetation and moisture-trapping soils.

• Reduces the amount of insolation used for evapotranspiration, which keeps the air cooler.

– Built surfaces have a lower albedo and therefore absorb the insolation.

• Narrow building arrangements create urban canyons that inhibit the escape of reflected radiation.

– Air conditioners, refrigerators, and industrial processes create heat that is released into the atmosphere.

Conventional paving materials can reach peak summertime temperatures of 48–67°C, transferring excess heat to the air

above them and heating stormwater.

Consequences• Increased urban

temperatures leads to… – Increased energy demands – Elevated Air Pollution

Emissions – Elevated Greenhouse Gas

Emissions – Compromised human

health and comfort – Impaired Water Quality

Solutions• Change the albedo by…

– Cool paving materials – Increasing tree and vegetative cover – Installing cool - mainly reflective - roofs – Creating green roofs

Proximity To Water• Water has a high heat capacity, which means…

…water heats up and cools down slowly • Coastal areas heat up and cool down slower than

inland. • Less variation in temperature than inland.

• Coastal areas heat up and cool down slower than inland. • Less variation in

temperature than inland.

What Can We Learn From Israel?

Cool and Dry

Hot and DryHot and Humid

It’s All About the Mountains!

• Mountains – Air rises up the mountains,

the warm, moist air expands and cools to form clouds and rain.

– Air coming down the mountain is dry and contracts so clouds can’t form.

• Elevation – Because we live in the troposphere, the temperature

decrease with altitude. – Mountain tops are cooler than sea level.

It’s All About the Mountains!

On the windward side there is rainy weather.

On the leeward side there is dry, desert conditions.

Atmospheric Convection Currents

Moving Things Around!• Air in the troposphere undergoes convection.

– Process of heat transfer that is driven by density differences.

• The characteristics of we use to describe an air mass are: – Humidity: Dry or humid – Temperature: Warm or cold

Less Dense = Rises More Dense = Sinks

Who is less dense, cold or warm?

Who is less dense, humid or dry?

Warm

Humid

Adiabatic Cooling• When air rises, it cools off

because of pressure changes.

• The gas molecules use energy to expand. – Less energy means that they

slow down.

• When there is less pressure, the air molecules are able to move around more freely. – They spread out and the air

parcel expands.

Temperature Decreases!

Condensation and Clouds

• As the air rises and cools, it gets cold enough for the water vapor to condense into water droplets.

• When condensation occurs, the molecules with the lowest amount of energy are leaving the gas. – Internal energy and temperature of the

gas increases. – Allows the parcel to continue to rise.

A Cloud Forms!!

The latent energy powers hurricanes!

• When evaporation occurs, the molecules with the greatest amount of energy are leaving the liquid. – Internal energy and temperature of the liquid decreases. – The energy taken with the gas is the latent heat of vaporization.

Air Pressure• Cold, dry air is more dense and therefore sinks.

– Air moves downward creating high air pressure.

• Warm, humid air is less dense and therefore rises. – Air moves upward creating low air pressure.

Let’s Draw Things Out!

H L H

1. Draw the following diagram on the bottom of your white board.

2. Draw what happens to the air above these locations using arrows.

4. Indicate where there would be poor weather with a rain cloud symbol and where it would be nice with a sun symbol.

5. Circle the arrows that would be considered the wind that we experience outside.

3. At the head of the arrows directly above the letters, indicate if the air is cooling or heating as it rises.

Let’s See How It Works Globally

Draw The Global Wind Patterns!

0°

30°

60°

30°

60°

L

H

L

H

L

H

H

NE Trade Winds

SE Trade Winds

Westerlies

Westerlies

Polar Easterlies

Polar Easterlies

Global Convection Cells