The Atmosphere

1. The Atmosphere Earth Science Spring 2013

2. Characteristics of the Atmosphere • Atmosphere- layer of gases & tiny particles that surrounds the earth • Study of the atmosphere is meteorology • Study: • Characteristics of the atmosphere • Weather- general condition of the atmosphere at a particular time & place including temperature, air movements, & moisture content • Climate – general weather conditions over many years

3. Characteristics of the Atmosphere • Composition • Most abundant elements in the atmosphere are the gases: nitrogen, oxygen, & argon • Most abundant compounds are: carbon dioxide & water vapor • Water vapor is added by evaporation & is removed by condensation & precipitation

4. Characteristics of the Atmosphere • Composition cont… • Ozone- oxygen molecules that has 3 oxygens • Protects the living things on earth from UV radiation of the sun • CFCs (chlorofluorocarbons) break down ozone • Atmospheric dust • Mineral particles lifted into the atmosphere by wind, ash from fires, volcanic dust, & some microscopic organisms

5. Characteristics in the Atmosphere • Oxygen in the Atmosphere • Animals, bacteria, & plants remove oxygen from the atmosphere as part of their life processes • Other things that remove oxygen: forest fires, burning of fuels, & the weathering of some rocks • Land & ocean plants produce oxygen through photosynthesis

6. Characteristics of the Atmosphere • Nitrogen in the Atmosphere • Amount of nitrogen in the air is maintained through the nitrogen cycle • Nitrogen cycle • Nitrogen moves from the air to the soil, to plants and animals, & back again to the air • Nitrogen is removed primarily by nitrogen-fixing bacteria

7. Characteristics of the Atmosphere • Atmospheric Pressure • Ratio of the force of the air to the area of the surface on which it puts pressure • Atmospheric pressure is high at lower altitudes & lower at higher altitudes • Gravity pulls of the gases of the atmosphere toward the earth’s surface & holds them there…the closer you are to the earth’s surface the more gravitational pull there is so the more air there is

8. Characteristics of the Atmosphere • Barometers • Barometer- instrument used to measure pressure • Mercurial barometer- well of mercury is pressed on by the air forcing it to rise up a tube to certain height • Pressure is measured in mm of mercury • 760mm Hg = 1 atmosphere which is standard atmospheric pressure (pressure at sea level) • Weather maps use millbars (mb)- 1 mb = 0.001 of standard atmospheric pressure

9. Characteristics of the Atmosphere • Barometers cont… • Aneroid barometer • Most commonly used today • No liquid in it • A sealed metal container with no air inside of it • Sides bend inward when pressure rises • Sides return closer to original shape as pressure drops • Can also measure altitude (altimeter)

10. Characteristics of the Atmosphere • Layers of the Atmosphere • Altitude ↑ Air pressure ↓ rapidly • Distinct differences in temperature with ↑altitude • Due to the way solar energy is absorbed as it moves downward though the atmosphere

11. Characteristics of the Atmosphere

12. Characteristics of the Atmosphere • Air Pollution • Air pollutant- any substance in the atmosphere that is harmful to people, animals, and plants • Sulfur dioxide, carbon dioxide, lead, & hydrocarbons • Main source is burning fossil fuels • coal • Petroleum fuels • Acid precipitation- when air pollutants becomes trapped in the atmosphere & return to the earth’s surface as precipitation • Temperature inversion- warm air on top of cool air prevents the cool air from escaping allowing air pollutants to concentrate

13. Solar Energy & The Atmosphere • Radiation • All the energy that earth receives from the sun travels through space between the earth and the sun as radiation. • Light is a form of radiation we can see • There are many forms of radiation we cannot see • Radiation travels through space in the form of waves at high speed

14. Solar Energy & The Atmosphere • Radiation cont... • Electromagnetic spectrum- complete range of wavelengths of radation • Wavelengths vary.... • Range from very long to very short • Almost all of the energy reaching the earth from the sun is in the form of electromagnetic waves • Almost all of the shorter wavelengths of the electromagnetic spectrum are absorbed in the upper layers of the atmosphere • Small amount of UV radiation reaches the Earth • Most of the radiation that comes through the atmosphere to the earth’s surface is infrared and visible light

15. Solar Energy & The Atmosphere • Scattering • Scattering is caused by clouds, dust, and gas molecules in the atmosphere • Scattering- when dust & water droplets trapped in the atmosphere reflect & bend the rays • Causes rays to bend and go in all different directions changing their wavelengths • Sends some back into space • Makes the sky appear blue

16. Solar Energy & The Atmosphere • Reflection • Of the solar energy reaching the earth • 20% absorbed by the atmosphere • 30% scattered back into space or is reflected from the clouds or the earth’s surface • 50% absorbed by the surface

17. Solar Energy & The Atmosphere • Absorption & Infrared Energy • Part of the absorbed radiation is made up of infrared rays • Warmth of the sun on your skin & other surfaces on the earth that are warm have absorbed infrared rays • Heated materials radiate their own infrared rays after they have absorbed them • Ex: warm rocks or concrete

18. Solar Energy & The Atmosphere • The Greenhouse Effect • When the earth’s atmosphere traps infrared rays over the earth’s surface • The visible & infrared rays of incoming sunlight pass through the water vapor & carbon dioxide of the atmosphere. • Most of the longer infrared rays sent out by the warmed surfaces on the earth are trapped by water vapor & carbon dioxide keeping them closer to earth • Causes the earth’s temperature to be much warmer than it would be without an atmosphere

19. Solar Energy & The Atmosphere • Variation in Temperature • Radiation from the sun does not heat the earth equally • Several factors affect how warm an area is: • Latitude (primary factor): the closer you are to the equator the more direct sunlight you receive • Elevation: high elevation is warmer during the day but becomes much cooler at night very quickly • Proximity to large bodies of water

20. Solar Energy & The Atmosphere • Conduction & Convection • Conduction • Molecules move faster as a substance is heated causing other molecules to move faster • Makes the substance warmer • Convection • Movement of liquids or gases when they are heated unevenly • Causes cooler air to push warmer air up

21. Winds • Pressure differences in the atmosphere at the equator and the poles create a general movement of air worldwide • Air moves from high-pressure belts toward low-pressure belts • Air typically moves from the poles toward the equator

22. Winds • Global Winds • Winds are strongly deflected by the Coriolis Effect • Winds that would blow directly from high-pressure to low-pressure areas are deflected • Convection cells- air flowing from the equator completes three looping patterns of air flow • Northern & Southern hemispheres each have 3 convection cells

23. Winds • Global Winds • Trade Winds • Wind flowing toward the equator from 30 degrees to 0 degrees latitude • Named according to the direction from which they flow • Northeast trades are deflected to the right by the Coriolis effect • Southeast trades are deflected to the left by the Coriolis effect • Doldrums- where the trade winds from the two hemispheres meet • Weak & unpredictable winds • Horse latitudes- descending air creates a high pressure belt near 30 degrees • Weak winds

24. Winds • Westerlies • Caused by air moving toward the poles being deflected by the Coriolis Effect • Found in both hemispheres • Northern Hemisphere- southwest winds • Southern Hemisphere-northwest winds • Located between 40 & 60 degrees latitude • Contiguous US is located within the westerlies • Hawaii is in the northeast trade winds • Parts of Alaska are in the polar easterlies

25. Winds • Polar Easterlies • Above 60 degrees latitude • Caused by subpolar lows • Subpolar lows are caused by warm air moving toward the poles & it is pushed up by the cold air moving toward the equator • Cause storms when they meet warm air from the westerlies forming polar fronts

26. Winds • Wind & Pressure Shifts • Positions of pressure belts & wind belts shift as the sun’s vertical rays shift northward & southward during the year • Some areas experience different wind belts during the year • Ex: Florida get westerlies in the winter & trade wind in the summer

27. Winds • Jet Streams • Upper westerly winds that are bands of high speed winds in the upper troposphere & lower stratosphere • Caused by large pressure differences due to the temperature differences between polar air and mid-latitude air • Polar jet streams control the paths of storms & affect air line routes

28. Winds • Local Winds • Not part of global wind belts • Breezes are light wind that extend over a distance of less than 100km • 2 types: • Land & sea breezes • Mountain & valley breezes

29. Winds • Land & Sea Breezes • Caused by temperature differences • Land heats up much more quickly than a large body of water creating a significant temperature different resulting in a significant pressure difference • Sea breeze- wind moving from water to land • Land breeze- wind moving from land to water

30. Winds • Mountain & Valley Breezes • Valley breeze- blows up the slopes during the daytime • Caused by warm air moving from the valley up the slope • Mountain breeze- blows down the slope in to the valley • Caused by cool air moving flowing down the slope