Download Weatherch16 notes - Clinton Public School District

Chapter 16 Notes 2014
1. Weather: is the condition of the Earth’ atmosphere at a particular time and place
2. Atmosphere: the layer of gases that surround the planet
3. Purposes of the Earth’s atmosphere:
a. traps energy from sun: atmosphere keeps most of the earth warm enough for water to
exist as a fluid
b. Makes conditions on earth suitable for living things
c. Protects living things from dangerous radiation
d. prevents earth’s surface from being hit by most meteoroids
4. Nitrogen is essential to living things: proteins and other complex chemicals substances in
living things contain nitrogen
Living things cannot use nitrogen directly from air: bacteria fix nitrogen into nitrates:
plants absorb nitrates from soil, use it to make proteins: to obtain proteins, animals must
first eat plants or other animals.
O2: diatomic: two atoms: natural state
O3: ozone: 3 atoms
5. water vapor: water in the form of a gas
6. pollutants: harmful substances in air, water or soil: most air pollution is result of burning
fossil fuels
7. Smog: brown haze: result of burning fossil fuels: photochemical
Fossil fuels burn: contain hydrocarbons: some of these hydrocarbons are not burned up
completely: some escape: at same time high temp that accompanies burning causes some of
the nitrogen to react with oxygen to form nitrogen oxide:
Nitrogen oxide, hydrocarbons and other air pollutants then react with each other in
presence of sunlight to form ix of ozone and other chemicals called photochemical smog.
8. Acid rain: forms when nitrogen oxide and sulfur oxides (from coal burning) combine with
water in the air to form nitric acid and sulfuric acid:
9. Nitrogen and oxygen are two most abundant in atmosphere.
Air has mass so it has density and pressure:
Density: amount of mass in a given volume of air is its density.
Density = mass
volume
Pressure: force pushing on an area or surface:
Denser substances have more mass per unit volume than less dense ones, so denser air exerts
more pressure than less dense air.
Air pressure is the result of the weight of a column of air pushing down on an area. Example:
weight of a column of air above your desk is about the same weight as a school bus: why
doesn’t it crush? The air pressure pushing down is balanced by air pushing up on bottom of
desk.
Falling air pressure indicates a storm approaching. Rising means weather is clearing
Barometer is an instrument used to measure change in air pressure.
Units of air pressure: barometers measure two ways
Inches of mercury: column of mercury
Millibars: one inch of mercury equal to 33.87 millibars, so 30 inches of mercury is
approximately equal to 1016 millibars
Altitude: elevation: distance above sea level: air pressure decreases as altitude increases: as
air pressure decreases so does density: Air pressure is greatest at sea level.
Layers of the atmosphere: 4 main layers that are classified by changes in temperature
1. troposphere: inner, lowest layer. Tropo meaning turning or changing: where earth’s
weather occurs. Weather balloons are partially inflated: Why? As balloon rises, air
pressure outside decreases and gas inside expands.
Depth of troposphere is 16 km above the equator to less than 9km above the north or
south pole. Shallowest layer but contains most all of the mass of the atmosphere.
Altitude increases, temperature decreases: every 1 km increase in altitude it becomes 6.5
degrees C cooler. At top of troposphere, temperature stops decreasing and stays constant
at about -60C. water here forms thin feathery clouds of ice.
2. stratosphere: starts at top of troposphere and goes to approximately 50 km above the
earth’s surface. Strato meaning: layer, spreading out
Lower stratosphere -60C, upper layer is warmer:
Contains a layer of ozone which absorbs energy from sun, converts it into heat, warming
air:
Weather balloon: as it rises thru stratosphere air pressure continues to decrease, gas
continues to increase, boom…..
3. Mesophere: Above stratosphere: drop in temperature marks beginning of the next layer
of atmosphere: Meso meaning middle
50 km from earth’s surface to 80 km above: in outer layer of mesosphere: -90C: this is
where shooting stars are seen. Mesosphere protects earth’s surface from being hit.
4. thermosphere: near top: air is very thin: 80 km above earth’s surface: no definite outer
limit:
Very hot: 1800C: energy from sun strikes thermosphere first: N and O molecules
convert energy into heat: ordinary thermometer would show below 0C because molecules are
so spread out they would be too far to collide with thermometer
Thermosphere has two layers:
A. Ionosphere: lower layer of thermosphere: 80 km to 550km. energy from sun causes
gas molecules in the ionosphere to become electrically charged particles called ions. Radio
waves bounce off ions in ionosphere and back to earth: AURORA BOREALIS occurs in
ionosphere which is caused by particles from sun that enter the ionosphere near the north
pole. These particles strike O and N in ionosphere causing them to glow.
B. Exosphere: 550 km outward for thousands of km. long distance calls, TV, signals may
have traveled up to satellite orbiting in exosphere and then back to your home.