The atmosphere is the thin layer of air that surrounds the earth. It is made up of various gases such as oxygen, nitrogen, carbon dioxides, dust particles, and water vapor. The gravitational force of the earth holds the atmosphere around it. It protects us from the harmful rays and scorching heat of the sun.
1. Overview of the Earth’s Atmosphere • The atmosphere, when scaled to the size of an apple, is no thicker than the skin on an apple. • The atmosphere is a gas. • The atmosphere is a fluid. • There is a surface but no “top” – the atmosphere gradually thins out with increasing altitude
2. Earth's Atmosphere Thin Gaseous envelope 99% of atmospheric gases, including water vapor, extend only 30 kilometer (km) above earth's surface. Most of our weather, however, occurs within the first 10 to 15 km.
3. Composition of the Atmosphere permanent gases • roles of nitrogen, oxygen and argon variable gases • role of water vapor trace gases • carbon dioxide, methane, ozone, CFCs, et al. aerosols
4. Composition of the Atmosphere The “dry atmosphere”: 78% N2, 21% O2, 1% Ar • N2 is primordial – it’s been part of the atmosphere as long as there’s been an atmosphere • O2 has been rising from none at all about 2.2 Gya – comes from photosynthesis • Ar40/Ar36 tells us that the atmosphere has been outgassed from volcanoes
5. Composition of the Atmosphere Water Vapor: H2O 0-4% • H20 can exist in all three phases at the surface of the Earth – solid, liquid and gas • Liquid or solid H2O can be suspended by atmospheric winds (clouds) or fall to the surface (precipitation) • VERY powerful greenhouse gas (both in vapor form and as clouds)
6. Composition of the Atmosphere The Hydrological Cycle
7. Table 1-1, p. 3
8. Composition of the Atmosphere Carbon dioxide • 390 ppm (by mass) and counting… • Natural and anthropogenic sources/sinks • Strong greenhouse gas (GHG) CO2 is neither the strongest atmospheric GHG pound-for-pound nor molecule-for-molecule… Why the fuss? CO2 is a product of the reaction that allows modern civilization to exist: combustion.
9. Fig. 1-4, p. 5
10. Composition of the Atmosphere The Global Carbon Cycle
11. Composition of the Atmosphere Methane • CH4 concentration: 1.8 ppmv • anthropogenic and natural sources/sinks too • powerful greenhouse gas • oxidizes rapidly, hence low concentrations • Large concentrations proposed to explain greenhouse warming of early Earth
12. Composition of the Atmosphere Ozone, CFCs and NOx Ozone (O3) • shields the surface from UV rays • produced by reaction with NOx and sunlight near the surface CFC’s (Chlorofluorocarbons) • destroy stratospheric ozone • chlorine is a catalyst: it destroys one O3 molecule and then is free to find another • Ozone at high altitudes (stratosphere) is “good”; ozone at low altitudes (troposphere) is “bad.”
13. Atmospheric Gases Nitrogen, oxygen, argon, water vapor, carbon dioxide, and most other gases are invisible. Clouds are not gas, but condensed vapor in the form of liquid droplets. Ground based smog, which is visible, Ozone – is the primary ingredient of smog! contains reactants of nitrogen and ozone.
14. Aerosols & Pollutants Human and natural activities displace tiny soil, salt, and ash particles as as well as sulfur and nitrogen oxides, and hydrocarbons as
15. Composition of the Atmosphere Aerosols • Dust • Sea-spray • Microbes Suspended particles in the atmosphere are responsible for cloud formation: water drops nucleate on them Cloud Condensation Nuclei (CCN)
16. Other Atmospheres YES NO Earth The Moon Mars all the other satellites Venus Mercury Jupiter asteroids Triton (Neptune’s moon) Titan (Saturn’s moon) The Sun
17. Other Atmospheres Planet Composition Temperature Pressure Venus CO2 96.5%, N2 750 K 90000 mb 3.5% Earth N2 78%, O2 21%, 290K 1000 mb Ar 1% Mars CO2 95%, N2 2.7%, 220K 10 mb Ar 1.6%
18. History of Meteorology Meteorology is the study of the atmosphere and its phenomena Aristotle wrote a book on natural philosophy (340 BC) entitled “Meteorologica” Sum knowledge of weather/climate at time Meteors were all things that fell from the sky or were seen in the air “meteoros” : Greek word meaning “high in air”
19. History of Meteorology Invention of weather instruments 1500’s Galileo invented water thermometer 1643 Torricelli invented mercury barometer 1667 Hooke invented anemometer 1719 Fahrenheit developed temp scale based on boiling/freezing water 1735 Hadley explained how the earth’s rotation influences winds in tropics 1742 Celsius developed the centigrade temp scale
20. History of Meteorology 1787 Charles discovered relationship between temp and a volume of air 1835 Coriolis used math to demonstrate the effect that the earth’s rotation has on atmos. Motions 1869 first isobars were placed on map 1920 concepts of air masses and weather fronts were formulated in Norway 1940’s upper air ballons/3-D view of atmos 1950’s high speed computers 1960 Tiros 1 first weather satellite
21. Vertical Structure of the Earth’s Atmosphere
22. Atmospheric Layers 8 layers are defined by constant trends in average air temperature (which changes with pressure and radiation), where the outer exosphere is not shown. 1. Troposphere 2. Tropopause 3. Stratosphere 4. Stratopause 5. Mesosphere 6. Mesopause 7. Thermosphere 8. Exosphere
23. Atmospheric Layers Tropopause separates Troposphere from Stratosphere. Generally higher in summer Lower in winter. Troposphere – Temp decrease w/ height Most of our weather occurs in this layer Varies in height around the globe, but Averages about 11 km in height.
24. The troposphere is the lowest major atmospheric layer, and is located from the Earth's surface up to the bottom of the stratosphere. It has decreasing temperature with height (at an average rate of 3.5° F per thousand feet (6.5 ° C per kilometer); whereas the stratosphere has either constant or slowly increasing temperature with height. The troposphere is where all of Earth's weather occurs. The boundary that divides the troposphere from the stratosphere is called the "tropopause", located at an altitude of around 5 miles in the winter, to around 8 miles high in the summer, and as high as 11 or 12 miles in the deep tropics. When you see the top of a thunderstorm flatten out into an anvil cloud, like in the illustration above, it is usually because the updrafts in the storm are "bumping up against" the bottom of the stratosphere
25. Atmospheric Layers Stratosphere Temperature inversion in stratosphere Ozone plays a major part in heating the air At this altitude
26. Atmospheric Layers Mesosphere Middle atmosphere – Air thin, pressure low, Need oxygen to live in this region. Air quite Cold -90°C (-130°F) near the top of mesosphere
27. Atmospheric Layers Thermosphere “Hot layer” – oxygen molecules absorb energy from solar Rays warming the air. Very few atoms and molecules in this Region. Figure 1.7
28. The Stratosphere and Ozone Layer Above the troposphere is the stratosphere, where air flow is mostly horizontal. The thin ozone layer in the upper stratosphere has a high concentration of ozone, a particularly reactive form of oxygen. This layer is primarily responsible for absorbing the ultraviolet radiation from the Sun. The formation of this layer is a delicate matter, since only when oxygen is produced in the atmosphere can an ozone layer form and prevent an intense flux of ultraviolet radiation from reaching the surface, where it is quite hazardous to the evolution of life. There is considerable recent concern that manmade flourocarbon compounds may be depleting the ozone layer, with dire future consequences for life on the Earth. The Mesosphere and Ionosphere Above the stratosphere is the mesosphere and above that is the ionosphere (or thermosphere), where many atoms are ionized (have gained or lost electrons so they have a net electrical charge). The ionosphere is very thin, but it is where aurora take place, and is also responsible for absorbing the most energetic photons from the Sun, and for reflecting radio waves, thereby making long-distance radio communication possible.
29. A Brief Look at Air Pressure and Air Density air density (ρ pronounced “row”) air pressure (p) sea-level pressure (ps) • Baseballs travel farther in higher-altitude air (Denver) than they do in lower-altitude air.
30. Pressure & Density Gravity pulls gases toward earth's surface, and the whole column of gases weighs 14.7 psi at sea level, a pressure of 1013.25 mb or 29.92 in.Hg. The amount of force exerted Over an area of surface is called Air pressure! Air Density is The number of air Molecules in a given Space (volume)
31. Vertical Pressure Profile rapidly with Climbing to an altitude of only 5.5 km where the pressure is 500 mb, would put you above one-half of the
32. Meteorology 101 Air Pressure “Top” On average, air weighs about 14.7 lb/in2 14.7 lb/in2 =29.92 “inches of mercury” 1” Air Pressure varies over the globe
33. Meteorology 101 Changing Pressure - Winds Take more out than put in – decrease pressure Put more in than take out – increase pressure
35. Meteorology 101 Rising Air near ows • Rising air cools; water vapor in the air condenses to form clouds/precipitation • Lows tend to bring cloudy, wet weather Sinking air near ighs • Sinking air warms and dries out. • Highs tend to bring fair, dry weather.
36. Meteorology 101 Some Fundamentals • Earth is heated unevenly: Tropics are warmer than the Polar Regions. • Nature tries to try to even out temperature differences. • Uneven heating sets atmosphere in motion and is the fundamental cause of all weather.
37. Meteorology 101 Ridge Upper- Level Trough Westerlies - High-Altitude winds blow generally west-to-east 3-6 miles above mid- latitudes. Jet Stream – River of fastest-moving air within the westerlies.
38. Meteorology 101 Reality is messier … Still, highs and Lows move with the westerlies and the jet stream.
39. Weather vs. Climate Weather is the dynamical way in which the atmosphere maintains the equilibrium climate.
40. Elements of Weather air temperature air pressure humidity clouds • Certain weather elements, like clouds, visibility and wind, are precipitation of particular interest to pilots. visibility wind
41. Climate Average weather • time-average • regional (spatial) average Extremes Trends Climate represents long-term (e.g. 30 yr) averages of weather.
42. A Satellite’s View of the Weather geostationary satellites • Atmospheric observation from satellites was an important technological development in meteorology. Other important developments include computers, internet, and Doppler radar.
43. Storms of all Sizes midlatitude cyclonic storms hurricanes and tropical storms thunderstorms tornadoes • Storms are very exciting, but they also play an important role in moving heat and moisture around throughout the atmosphere.
44. Impacts of Weather 1/5
45. Impacts of Weather 2/5
46. Impacts of Weather 3/5
47. Impacts of Weather 4/5 146 people die each year in US from flash
48. Impacts of Weather 5/5 Lightning strikes earth 100 times every second
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