THE ATMOSPHERE

Weather & Atmosphere

What does the weather forecast say?

36°F | 2°C Condition: Clear Humidity: 65% Wind: N at 2 mph

1. THE AIR AROUND YOU Weather is the

condition of Earth’s atmosphere at a particular time and place.

Earth’s atmosphere is the envelope of gases that surrounds the planet.

Composition of the Atmosphere

1.Nitrogen: (N2) ¾ of the air we breath (Most abundant

gas) Nitrogen molecule has 2 atoms of Nitrogen

2.Oxygen:

Less than ¼ of the volume. It is involved in other processes

Oxygen molecules (O2) has 2 atoms of oxygen.

Ozone (O3) is a form of oxygen that has 3 atoms of Oxygen

Antoine-Laurent Lavoisier has been called the founder of modern chemistry，1743.8.26-1794.5.8. French

Among his important contributions were the application of the balance and the principle of conservation of mass to chemistry, the explanation of combustion and respiration in terms of combination with oxygen.

3.Carbon Dioxide: Each molecule of CO2 has 2 atoms of

oxygen and 1 of carbon. It is essential to life (plants).

4.Other gases: Argon (Ar) etc. Remain gases are called trace gases,

because only small amounts of them are present.

5.Water vapor: Air is not dry because it contains water

vapor Important role in the Earth’s weather.

6.Particles: Pure air only exists in laboratories. In the real world air contains: dust,

smoke, salt, chemicals… Importance of the atmosphere

Earth’s atmosphere makes conditions on Earth suitable for living things. (Water, Energy, Mild temperatures, radiation and meteorites protection)

2. AIR PRESSURE

The weight of the atmosphere itself is constantly pressing on your body (I.e.: backpack)

Properties of air Air has mass Density

density= mass/volume• (More molecules, greater density)

Pressure• The force pushing on

an area or surface• Air pressure is the

result of the weight of a column of air pushing down on an area.

• Denser substance has more mass per unit volume than a less dense one, so denser air exerts more pressure than less dense air

Measuring Air Pressure Barometer is an

instrument that is used to measure air pressure. There are 2 types:• Mercury barometer (At sea level the mercury

column is about 760mm high on average)

• Aneroid Barometer (Aneroid means without

liquid)

Units of Air Pressure• milibar (mbar or mb)• Atmosphere (atm)• 1atm= 1060 mbar• 1atm= 760 mmHg or Torricelli (tor)

Altitude is the distance above sea level. Air pressure decreases as altitude increas

es As air pressure decreases, so does

density (I.e.: air at the top of a mountain).

3. LAYERS OF THE ATMOSPHERE Scientist divide Earth’s atmosphere into four

main layers classified according to changes in temperature. These layers are: The troposphere The stratosphere The mesosphere The Thermosphere

• The Ionosphere• The Exosphere

The Troposphere Earth’s weather occurs here. Tropo- means “turning” The depth varies in the equator(9 Km)

and in the poles(15Km). It contains almost all of the mass of the

atmosphere As altitude increases in it, the

temperature decreases.

The Stratosphere It extends from the top of the troposphere to

about 50 km above earth’s surface.

It contains the ozone layer (O3).

Lower stratosphere colder than the upper.

The ozone protects Earth’s living things from dangerous ultraviolet radiation from the Sun.

The Mesosphere A drop in the temperature marks the

beginning of the next layer.

Meso means “middle”

It is the layer of the atmosphere that protects Earth’s surface from being hit by most meteoroids.• Meteoroids are chunks of stone and metal from

space.

The Thermosphere Near the top of the atmosphere, the air

is very thin. It has no outer limit Thermo means “heat”. Air in here is very

hot, because sunlight strikes it first.

The Thermosphere is divided into two layers: The lower layer is called the Ionosphere: The outer layer is called the Exosphere:

• Temperature is the average amount of energy of motion of each molecule of a substance

The Thermosphere is divided into two layers:

The lower layer is called the Ionosphere: It begins about 80 km above the surface

and extends to about 400 km. Energy from the Sun causes gas

molecules in the ionosphere to become electrically charged particles called ions.

Radio waves bounce off ions in the ionosphere back to Earth’s surface.

Northern lights or Aurora Borealis occur here. They are caused by particles from the Sun that enter the ionosphere near the poles. These particles strike atoms in the ionosphere, causing them to glow.

The outer layer is called the exosphere: It is the outer portion of the

thermosphere. It extends from about 400 km outward for

thousands of km.

4. AIR QUALITY Not everything

in the air is healthy(tiny particles or small amount of harmful gases)

Pollutants are harmful substances in the air, water or soil.

POLLUTANT SOURCE HEALTH EFFECT

CO2Burning of fossil fuels Reduced ability of

blood to deliver oxygen to cells

Nitrogen dioxide

Burning of fossil fuels Breathing problems, lung damage

Ozone Chemical reaction of certain carbon compounds

Breathing problems, asthma, eye irritation

Particles of dust, smoke or soot

Burning of wood and fossil fuels, volcanic eruptions

Respiratory illnesses, nose and throat irritation

Sulfur dioxide

Burning of fossil fuels, volcanic eruptions

Breathing problems, lung damage

Sources of Pollution Natural sources: forest fires, soil erosion and

dust storms release a great deal of smoke and dust into the air.

Human activities: such as farming and construction, can send soil and dust into the air. Most air pollution is the result of burning fossil fuels (half from motor vehicles, the other from factories, power plants…).

Burning fossil fuels produces a variety of pollutants, including carbon monoxide, nitrogen oxides and sulfur oxides.

Smog and Acid Rain Caused by the burning of fossil fuels London-type Smog

• 100 years ago “dirty” air in London (coal burning)• Air was full of soot• Smog= smoke and fog (describe this air pollution)

Photochemical Smog• The brown haze that develops in sunny cities is

called photochemical smog. It is formed by the action of sunlight on pollutants such Hydrocarbons and nitrogen oxides (Brownish mixture of ozone and other pollutants)

• Ozone in the stratosphere is good, but it in the troposphere is a pollutant.

LONDON TYPE SMOG

PHOTOCHEMICAL SMOG

Acid Rain• When rain contains more acid than normal.• It forms when nitrogen oxides and sulfur oxides

combine with water in the air to form nitric and sulfuric acid.

• Sometimes strong enough to damage the surfaces of building and statues, but also affects water.

AIR QUALITY

AIR QUALITY INDEX (AQI) The AQI is an index for reporting daily air

quality. It tells you how clean or polluted your air is,

and what associated health effects might be a concern for you.

The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air

Where to check Beijing AQI: http://iphone.bjair.info/ (From US Beijing

embassy) Improving Air Quality

Law and regulation to reduce air pollution (in some countries such as US)

Voluntary measures:• Car pooling• Public transport• Better design of factories (recycling systems…)