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. 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