The Earth and Its Atmosphere. Chapter 1

Transcription

1 The Earth and Its Atmosphere Chapter 1

2 Overview of the Earth s Atmosphere The atmosphere is a delicate life giving blanket of air surrounding the Earth. Without the atmosphere the Earth would not have lakes or oceans. Radiant energy from the sun energizes the atmosphere driving day to day weather.

3 Composition Overview of the Earth s Atmosphere 99% of the atmosphere is within 30km of the Earth s surface N 2 78% and O 2 21% The percentages represent a constant amount of gas but cycles of destruction and production are constantly maintaining this amount.

4

5 Overview of the Earth s Composition Atmosphere Water a variable gas following the hydrologic cycle. Carbon dioxide has risen in recent years and is an important greenhouse gas. Other greenhouse gases exist beyond carbon dioxide.

6 The main components of the atmospheric carbon dioxide cycle. The gray lines show processes that put carbon dioxide into the atmosphere, whereas the red lines show processes that remove carbon dioxide from the atmosphere.

7 Stepped Art

8 (a) The solid blue line shows the average yearly measurements of CO2 in parts per million (ppm) at Mauna Loa Observatory, Hawaii, from 1958 to The jagged dark line illustrates how higher readings occur in winter where plants die and release CO2 to the atmosphere, and how lower readings occur in summer when more abundant vegetation absorbs CO2 from the atmosphere. (b) The insert shows CO2 values in ppm during the past 1000 years from ice cores in Antarctica (orange line) and from Mauna Loa Observatory (blue line). (Mauna Loa data NOAA-Ice Core data courtesy of Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory

9 The darkest color represents the area of lowest ozone concentration, or ozone hole, over the Southern Hemisphere on September 25, Notice that the hole is larger than the continent of Antarctica. A Dobson unit (DU) is the physical thickness of the ozone layer if it were brought to the earth s surface, where 500 DU equals 5 millimeters.

10 Variable components of air Ozone Three atoms of oxygen (O 3 ) Distribution not uniform Concentrated between 10 and 50 km above the surface Absorbs harmful UV radiation Human activity is depleting ozone by adding Chlorofluorocarbons (CFCs)

11 Ozone Depletion

12 Variable components of air Water vapor Up to 4% of air s volume Forms clouds and precipitation It is also a greenhouse gas Important role in absorbing and releasing latent heat during phase change Aerosols Tiny solid and liquid particles Water vapor can condense on solids Reflect sunlight Color sunrise and sunset

13 Overview of the Earth s Atmosphere The Early Atmosphere The Earth s first atmosphere was composed mostly of hydrogen and helium. The atmosphere evolved due to outgassing of CO 2 and H 2 O from the cooling center of the Earth causing rain and eventually lakes and oceans. Lakes and oceans acted as a sink, absorbing CO 2 from atmosphere. Plants evolved producing oxygen to form our current atmosphere several 100 million ybp.

14 Vertical Structure of the Atmosphere Air Pressure and Air Density Weight = mass x gravity Density = mass/volume Pressure = force/area At the Earth s surface the pressure of the atmosphere is 14.7 lbs/in 2. Standard sea level pressure is mb = hpa = in Hg Atmospheric pressure decreases with an increase in height.

15 Both air pressure and air density decrease with increasing altitude. The weight of all the air molecules above the earth s surface produces an average pressure near 14.7 lbs/in.2

16 Atmospheric pressure decreases rapidly with height. Climbing to an altitude of only 5.5 km, where the pressure is 500 mb, would put you above one-half of the atmosphere s molecules.

17 Vertical Structure of the Atmosphere Lapse rate = change in temperature with a change in height Isothermal environment = no change in temperature with height Inversion layer = change in the sign of the lapse rate

18 Near the earth s surface the air temperature lapse rate is often close to 3.5F per 1000 ft. If this temperature lapse rate is present and the air temperature at the surface (0 ft) is 46F, the air temperature about 4000 ft above the surface would be at freezing, and snow and ice might be on the ground.

19 Vertical Structure of the Atmosphere Layers of the Atmosphere Troposphere: decrease in temperature, day to day weather, tropopause Stratosphere: increase in temperature, ozone, stratopause Mesosphere: decrease in temperature, mesopause Thermosphere: increase in temperature, suns strongest radiation

20 Troposphere Bottom layer Temperature decreases with altitude Environmental lapse rate Average 6.5 C per km or 3.5 F per 1000 feet Thickness varies Average height is about 12 km Outer boundary is the tropopause Where weather happens!

21 Stratosphere 12 to 50 km Temperature increases at top Outer boundary is the stratopause Mesosphere 50 to 80 km Temperature decreases Outer boundary is the mesopause Thermosphere No well-defined upper limit Fraction of atmosphere s mass Gases moving at high speeds

22 Layers of the atmosphere as related to the average profile of air temperature above the earth s surface. The red line illustrates how the average temperature varies in each layer. Stepped Art

23 Special Topic: The Atmospheres of Other Planets Each planet s atmosphere is unique in terms of temperature and composition. Earth: N 2, O 2 Venus: 95% CO 2, thick Mars: 95% CO 2, thin Jupiter: H 2, He, Red Spot

24 Vertical Structure of the Atmosphere Observation: Radiosonde Weather balloon Instrument and transmitter Air temperature, humidity, pressure

25 Vertical Structure of the The Ionosphere Atmosphere Not a true layer but an electrified region Ions = molecule with an additional or minus an electron Exists at the top of the atmosphere in the thermosphere F,E,D layer Sun light creates layers, D disappears at night and less interference with AM radio transmissions.

26 At night, the higher region of the ionosphere (F region) strongly reflects AM radio waves, allowing them to be sent over great distances. During the day, the lower D region strongly absorbs and weakens AM radio waves, preventing them from being picked up by distant receivers.

27 (left) Layers of the atmosphere based on temperature (red line), composition (green line), and electrical properties (dark blue line). (An active sun is associated with large numbers of solar eruptions.)

28 Weather and Climate Weather: short term Air temperature Air pressure Humidity Clouds Precipitation Visibility Wind Climate: long term patterns and average weather; not just magnitude but also frequency

29 Weather & Climate Meteorology brief history Study of the atmosphere and its phenomena Aristotle 340 B.C. Meterologica, meteoros: high in air 1843 telegraph 1920s air masses 1940s upper air 1950s radar and computers 1960s satellite

30 Doppler radar has the capacity of estimating rainfall intensity. In this composite image, the areas shaded green and blue indicate where light-tomoderate rain is falling. Yellow indicates heavier rainfall. The red-shaded area represents the heaviest rainfall and the possibility of intense thunderstorms. (Notice that a thunderstorm is approaching Chicago from the west.)

31 Weather & Climate Satellite s View Geostationary satellite 22,300 mi above equator Meridians measure longitude (W-E) Parallels measure latitude (N-S) Weather maps: pressure cells, fronts, surface stations

32 This satellite image (taken in visible reflected light) shows a variety of cloud patterns and storms in the earth s atmosphere.

33 Simplified surface weather map that correlates with the satellite image shown in Fig The shaded green area represents precipitation. The numbers on the map represent air temperatures in o F.

34 Weather & Climate Weather and Climate in Our Lives Two general reasons for studying how weather and climate impacts our lives: economic efficiency and public safety. Clothing Crops Utilities Extreme cold and heat Tornados and hurricanes

35 Ice storm near Oswego, New York, caused utility poles and power lines to be weighed down, forcing road closur

36 A tornado and a rainbow form over south-central Kansas during June, White streaks in the sky are descending hailstones. Flooding during April, 1997, inundates Grand Forks, North Dakota, as flood waters of the Red River extend over much of the city. Estimates are that lightning strikes the earth about 100 times every second. About 25 million lightning strikes hit the United States each year. Consequently, lightning is a very common, and sometimes deadly, weather phenomenon.