Weather Chapter 1 The Atmosphere What is weather

Weather - Chapter 1 The Atmosphere

What is weather? Refers to the state of the atmosphere at a specific time and place. The one thing that you can talk to anybody about! If you don’t like the weather just wait around it will change!

1. 1 The Air Around You u. Weather is constantly changing u. The atmosphere is the envelope of gases that surrounds the planet

Composition of the atmosphere NITROGEN (N 2): 78% n OXYGEN (O 2): 21% n Other: 1% n CARBON DIOXIDE n WATER VAPOR n METHANE n ARGON PARTICLES (dust, smoke, salt, chemicals) n n

Atmosphere Characteristics • Water vapor is the source of all clouds and precipitation. Like carbon dioxide, water vapor absorbs heat given off by Earth. It also absorbs some solar energy.

Ozone is a form of oxygen that combines three oxygen atoms into each molecule (O 3). n If ozone did not filter most UV radiation and all of the sun’s UV rays reached the surface of Earth, our planet would be uninhabitable for many living organisms. n It forms when lightening interacts with oxygen in the air.

1. 2 Air Pressure n Properties of Air n Because air has MASS, it also has other properties, including DENSITY and PRESSURE. n Density n D = M/V n Pressure- the force pushing on an area or surface. n Air Pressure- The result of the WEIGHT OF A COLUMN OF AIR PUSHING DOWN on an area. n Air pressure changes from day to day. Denser air exerts more pressure than less dense air.

– Measuring Air Pressure • Barometer – an instrument that is used to MEASURE AIR PRESSURE. – Two common kinds: 1. MERCURY Barometers-glass tube open at the bottom end and partially filled with mercury » Mercury is pushed higher with more air pressure.

2. ANEROID Barometers-air tight metal chamber that is sensitive to changes in pressure. n METAL SPRING AND DIAL n Fig 6, page 13

Measuring air pressure - units n n Several different units used Most use – inches of mercury (Hg) n n Based on the height of the column of Hg in a Hg barometer. “ 30 inches of mercury” National Weather Service indicates pressure as millibars n 1 inch of Hg = 33. 87 millibars eg. 30 in Hg = 33. 87 millibars = 1, 016 millibars 1 in of Hg Hectopascal (symbol h. Pa) is a SI unit, one millibar is equivalent to 100 pascals or one hectopascal. 1 mb = 1 h. Pa

Altitude and Air Pressure n Altitude and properties of Air n Altitude: ELEVATION OR DISTANCE ABOVE SEA LEVEL n Altitude and Air Pressure/Density: n INVERSELY PROPORTIONAL n Increase in ALTITUDE = Decrease in air PRESSURE, LESS air pushing down from above you.

Altitude and Density n The density of air decreases as altitude increases. Air at sea level has more gas molecules in each cubic meter than air at the top of a mountain.

Graphic Organizer Air Pressure decreases as measured in measured with units of Millibars Density decreases Altitude increases Inches of mercury Barometers include Aneroid Mercury

1. 3 Layers of the Atmosphere

Layers of the atmosphere n n There are 4 layers in the atmosphere classified according to temperature changes. They are the troposphere, stratosphere, mesosphere, and thermosphere.

Troposphere • This is the layer that is closest to the surface of the earth • It’s elevation ranges from 0 to 12 km • Weather only occurs here

Stratosphere n n n This layer sits on top of the troposphere It’s elevation ranges from 12 km to around 50 km This layer contains the ozone layer, which protects the earth from ultraviolet radiation from the sun.

Mesosphere n n n This layer is above the stratosphere It’s elevation ranges from 50 to 80 km This layer protects the earth from getting hit from asteroids

n n Thermosphere This is the highest layer of the atmosphere It’s height ranges from 80 to 400 km This is where most small meteorites burn up and is also the location in the atmosphere that the northern lights occur (aurora borealis) It is divided into the ionosphere (lower layer) and exosphere (upper layer)

Changing Temperatures n n The graph shows how temperatures in the atmosphere change with altitude. Use it to answer the questions that follow.

Changing Temperatures What two variables are being graphed? In what unit is each measured?

Changing Temperatures Temperature and altitude degrees Celsius and kilometers

Graph Analysis n n n What is the temperature at the bottom of the stratosphere? Which layer of the atmosphere has the lowest temperature? Describe how temperature changes as altitude increases in the troposphere.

1. 4 Air Quality n n Pollutants- harmful substances in the air, water and soil They can affect human health and other things

Sources of Pollution Natural sources- forest fires, soil erosion and dust storms. Wind carries particles of mold and pollen. Volcanoes emit clouds of gas, dust, and ash. Human activities- farming, construction, burning of fossil fuels (coal, oil, gas, diesel fuel) Fossil fuels produce a variety of pollutants including carbon monoxide, nitrogen oxides and sulfur oxides

Smog and Acid Rain n Burning of fossil fuels can cause smog and acid rain London-Type Smog- created when particles in coal smoke combine with water droplets in humid air Photochemical Smog- brown haze formed by the action of sunlight on pollutants such as hydrocarbons and nitrogen oxides. This is a combination of ozone and other pollutants.

n n n Acid Rain- forms when nitrogen oxides and sulfur oxides combine with water to form nitric acid and sulfuric acid. Rain, sleet, snow, fog and dry particles can carry these acids to trees and lakes. It can damage buildings and statues and can make water inhabitable for plants and organism.

Before and After

Effects of Pollution n Air pollution cause many different problems. This table shows the health effects of air pollution. Pollen also can cause difficulties for people with allergies.

Improving Air Quality n n The Environmental Protection Agency (EPA) monitors air pollutants in the United States. New model cars and power plants produce fewer pollutants than older models. Cities are still polluted because there are more power plants and cars with the increase in population. Reducing pollution can be very expensive.