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Chapter 17 Outline Follow along and fill in your handouts.

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1 Chapter 17 Outline Follow along and fill in your handouts

2 1)Atmosphere Characteristics a)Weather- State of the atmosphere at any given time or place b)Climate- The observations of weather that have been recorded over many years c)The most important measureable parts of weather and climate are i)Air temperature ii)Humidity iii)Type and amount of precipitation iv)Air pressure v)Speed and direction of wind

3 2) Atmospheric Composition a)Started as gasses emitted during volcanic eruptions 4.6 billion years ago b)Oxygen accumulation began 2.5 billion years ago c)Major Components i)78 % Nitrogen and 21% Oxygen ii).93% Argon and.07% Carbon Dioxide iii)Carbon Dioxide is a greenhouse gas and absorbs energy from the Sun and Earth

4 d) Variable Components include water vapor, dust particles and ozone. These have significant impact on weather and climate i)Water vapor varies from 0-4% in the atmosphere ii)Water vapor is the source of all clouds and precipitation iii)Water vapor absorbs heat energy from the Earth and Sun iv)Microscopic particles include salts, dust, smoke, soot, pollens, microorganisms and ash from volcanoes e) Ozone- Form of oxygen that combines three oxygen atoms into one molecule (O ₃ ) i)Ozone is formed when a single oxygen (O) collides with an oxygen molecule (O ₂ ) in the presence of a neutral molecule ii)Ozone concentration is 10 to 50kms above Earth’s surface iii)Ozone layer absorbs harmful UV radiation from the Sun

5 f) Human Influence i)Air pollutants are airborne particles and gasses that endanger the health of organisms ii)Primary pollutants are emitted directly from identifiable sources iii)Transportation vehicle emissions account for nearly half of primary pollutants iv)Secondary pollutants are produced by reactions between primary pollutants in the atmosphere

6 3) Height and Structure of the Atmosphere a)The atmosphere thins as you travel away from Earth until there are too few gas molecules to detect b)Pressure Changes i)Atmospheric pressure is caused by the weight of the air above ii)Sea Level is slightly more than 1kg per cm² iii)Half of the mass is below 5.6km

7 c)Temperature Changes i)Atmosphere can be divided into four layers based on temperature ii)Atmosphere becomes colder as elevation rises in the troposphere iii)All important weather phenomena takes place in the troposphere iv)Layer is approximately 12km thick v)Temperature begins to increase with height in the stratosphere vi)Ozone layer exists in this layer. vii)Layer continues to approximately 50km above the surface of the Earth viii)Temperatures fall with height in the Mesosphere ix)Temperature drop to approximately -90c° x)Layer continues to a height of 80km above the Earth xi)Temperature increases in the last layer, the thermosphere

8 4) Earth-Sun Relationships a)Solar energy is not distributed evenly over the Earth’s surface b)Unequal heating of the Earth drives the winds and ocean currents c)Earth’s Motions i)Two principal motions- rotation and revolution ii)Rotation is the spinning of the planet along its axis iii)Revolution is the travelling of the planet around the Sun d)Earth’s Orientation i)Seasonal changes occur because Earth’s position relative to the Sun continually changes as it travels along its orbit ii)Earth is tilted 23.5° away from perpendicular iii)Axis always point towards the North Star

9 e)Sun’s Apparent Path i)The changing orientation during the orbit causes the Sun’s angle to change with the season ii)47° change in angle of sun between winter and summer f)The Seasons i)Approximately June 21 or 22 the northern hemisphere reaches maximum tilt towards the Sun. This is the Summer Solstice (first day of summer) ii)Approximately December 21 or 22 the northern hemisphere reaches maximum tilt away from the Sun. This is the Winter Solstice (first day of winter) iii)Midway between the solstices are the equinoxes iv)Autumnal Equinox = September 22 or 23 v)Spring Equinox= March 21 or 22 vi)Earth’s axis is vertical during equinox

10 g) Length of Daylight i)Daylight vs. dark determined by the tilt of the axis ii)12 hours of daylight and dark during the equinox iii)Daylight hours increase as the northern hemisphere approaches the Summer Solstice iv)Daylight hours decrease as the northern hemisphere approaches the Winter Solstice

11 1. Heating the Atmosphere a.Heat- the transfer of energy from one object to another because of the difference in their temperature b.Temperature- measure of the average kinetic energy of the atoms in a substance c.Temperature increases as the atomic movement increases

12 2. Energy Transfer a.Conduction i.Transfer of heat energy through molecular activity ii.Requires direct contact iii.Heat flows from warm areas to cold areas iv.Air is not a good conductor v.Conduction only takes place between air and the surface of the Earth

13 b. Convection i.Transfer of heat energy by mass movement or circulation ii.Takes place in fluids or substances that act like fluids iii.Substance is warmed by conduction, expands and rises iv.Rising substance forces cooler, more dense substance to sink v.Cooler substance is then heated through conduction and rises

14 c. Radiation i.Transfer of heat energy through electromagnetic waves ii.Light and heat energy small part of electromagnetic spectrum iii.Travels in all directions from the source iv.Can travel through a vacuum v.All objects emit radiant energy vi.Hotter objects emit more total energy per unit are than cooler objects do vii.The hottest radiating bodies produce the shortest wavelengths of maximum radiation viii.Objects that are good absorbers are good emitters as well

15 3. What Happens to Solar Radiation? a.Absorption i.About 50% of solar radiation reaches Earth’s surface and is absorbed ii.Most is then radiated into the atmosphere iii.Gas molecules in the atmosphere absorb some of the heat energy and then re-emit it to the Earth (Greenhouse Effect) iv.Without Greenhouse Effect, planet not livable b.Transmission

16 c. Reflected i.Electromagnetic waves bounce off of a substance ii.Scattering produces a large number of weaker waves iii.Scattering is responsible for the blue sky iv.Most energy is dispersed in the forward direction v.About 30% of solar energy reflected into space d. Photosynthesis i.Solar energy absorbed by chlorophyll and used to produce plant food ii.Solar energy responsible for all life on Earth

17 1.Why Temperatures Vary a.A temperature control will cause temperature to vary from place to place and time to time b.Latitude influences the angle of the Sun’s rays and the length of the daylight hours throughout the year. c.Heating of land vs. water i.Land heats more rapidly and to higher temperatures than water ii.Land cools more rapidly and to lower temperatures than water iii.Greater variations of temperature over land iv.Cities that are close to large bodies of water will have a much more consistent year-round temperature

18 d. Geographic Position i.Wind direction will greatly influence temperature 1.Wind from ocean = temperature characteristics of the ocean 2.Wind from the land = temperature characteristics of the land ii.Mountains act as a barrier to weather patterns iii.Altitude changes average temperature -3.5° for every 1000 feet in elevation e. Cloud Cover and Albedo i.Albedo- the amount of radiation that is reflected by a surface ii.Many clouds have high albedo and reflect much of the radiation back into space during the daylight hours iii.At night, clouds act like a blanket and hold the heat energy in

19 2. World Temperature Distribution a.Isotherms- lines that connect points that have the same temperature b.Maximum temperature at the equator and cools towards that poles c.Temperature decreases as latitude increases

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