Chapter 17: The Atmosphere: Structure & Temperature 17:1 Atmosphere Characteristics

Weather What is weather? What is climate? Weather is constantly changing, and it refers to the state of the atmosphere at any given time and place. It is a day to day condition. Weather conditons in a certain area averaged oer a long period oft time. What is the climate of Knightdale? Hot and humid

Climate

Most Important Measurable Properties of Weather & Climate Air Temperature Humidity Type and amount of precipitation Rain, sleet, snow Others?

Composition of the Atmosphere What are the major components of the air? Nitrogen makes up about 78% of our air Oxygen makes up about 21% of our air

Temperature Changes The atmosphere is divided into four layers Ozone layer

Layers of the Atmosphere Troposphere – 1st layer Called “weather layer “ because all weather occurs here Has temperature to sustain life , average 70 degrees F Stratosphere – 2nd layer Ozone layer is concentrated here Ozone combines three oxygen atoms into each molecule (O3) Ozone absorbs UV rays from the Sun Without ozone layer we would see an increase in skin cancer Without ozone, our planet would be uninhabitable for many living organisms

Layers of the Atmosphere Mesosphere – 3rd layer “middle layer Temp decreases with height More than 80 km above the Earth Temps here approach –90 degrees C Thermosphere – 4th layer- “thermo” means heat Contains only a fraction of the atmosphere’s mass Temps increase here b/c oxygen and nitrogen absorb short wave, high energy solar radiation

Ozone Layer The ozone layer is crucial to life on earth What does ozone do for you? Ozone absorbs potentially harmful UV radiation from the sun If ozone did not filter most UV radiation and all the sun’s UV rays reached the surface of the earth, our planet would be uninhabitable for many living organisms How is Ozone destroyed? Propellants (CFCs) in spray cans break down ozone

Primary Pollutants What is the major pollutant in our atmosphere? Primary pollutants are emitted directly from from identifiable sources Emissions from transportation account for nearly 50% of primary pollutants in atmosphere Carbon Monoxide

Air Pollutants Air pollutants are air borne particles and gases that occur in concentrations large enough to endanger the health of organisms

Temperature Changes The pictures of snow capped mountains rising above snow free valleys show us that Earth’s atmosphere becomes colder as you climb higher

Earth-Sun Relationships What drives the Earth’s weather and climate? How? Solar energy is not distributed evenly over Earth’s surface. These are caused by the motions of Earth relative to the Sun and by variations in Earth’s land and ocean surfaces The Sun, the uneven heating of the Earth

Earth & Sun Relationships Earth has two principal motions Rotation – the spinning of Earth about it’s axis Revolution – the movement of Earth in it’s orbit around the Sun

Earth’s Orientation We know that it is colder in winter than summer, but why? Earth is tilted on it’s axis – 23.5 degrees What would happen if the Earth was not tilted? - Length of day and a gradual change in the angle of the noon sun above the horizon affect the amount of energy the Earth receives - We would not have any seasons…

Earth’s Tilt & Sun’s Rays

Alaska… Summer Solstice This is the midnight summer solstice – June 21st

Solstices On June 21st each year the axis is such that the Northern Hemisphere is “leaning” 23.5 degrees toward the Sun This is known as the summer solstice, or first “official” day of summer December 21st – Northern Hemisphere is “leaning” 23.5 degrees away from the Sun Winter Solstice – first “official” day of winter

Solstices & Equinoxes

Equinoxes March 21st September 22nd Spring (Vernal) Equinox September 22nd Autumnal Equinox Both – the Sun’s rays are hitting the equator, right on the money & the time of actual daylight equals the time of no daylight