Jon Ahlquist 9 14 2006 Chapter 1 The Earth and Its Atmosphere Solar System p 2 figure not to scale Overview of the Earth s atmosphere The solar system of the atmosphere greenhouse gases The early atmosphere Composition Vertical structure of the atmosphere A brief look at air pressure and air density Layers of the atmosphere The radiosonde weather balloon 1st 4 planets are small and rocky Mercury looks like Earth s moon Venus covered with clouds surface is hundreds of degrees hot Earth 93 million miles from Sun 8 min for light to travel to Earth Mars Asteroid belt not shown in figure 4 gas giants Jupiter and Saturn Uranus Neptune 1st letters of last 3 spell SUN Pluto dwarf planet rock water ice frozen methane Asteroid belt between Mars Jupiter Weather and climate Meteorology A brief history view of the weather Weather climate in our lives Satellite s Remembering Order of Planets Atmospheric Composition pp 2 8 You can use the following sentence to help you remember the order of the nine planets My very educated mother just showed us nine planets Each word of the preceding sentence begins with the letter of the next planet as you go out from the Sun Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto As of August 2006 Pluto was reclassified as one of several dwarf planets because a number of other small similar bodies have been identified beyond Neptune Greenhouse gases pp 5 6 more in chap 2 The two most important greenhouse gases water vapor H20 about 1 of atmosphere and carbon dioxide CO2 about 0 04 We ll say more in chapter 2 Amount of CO2 has been steadily increasing due to burning Graph below shows last 50 years Also note annual cycle in CO2 lower in summer when plants absorb more CO2 higher in winter when plants die and release CO2 Greenhouse gases cont Methane produced by plants animals Nitrous oxide laughing gas Ozone O3 i e 3 oxygen atoms Chlorofluorocarbons CFCs 1965 1975 1985 MET1010 Intro to the Atmosphere 1995 2005 Other important greenhouse gases that are trace gases Fig 1 5 p 6 CO2 amount Year 1958 Hydrogen primary component of Sun gas giant planets Hydrogen almost certainly primary component of Earth s early atmosphere but gravity on Earth other inner planets not strong enough to prevent escape of hydrogen to space Earth s current atmosphere probably developed from volcanic gases outgassing from volcanoes Earth s air roughly 80 nitrogen N2 and 20 oxygen O2 Next most abundant gases are water vapor and argon type of inert gas each about 1 of atmosphere Other gases present in minute amounts much less than 1 trace gases Some are greenhouse gases which influence the Earth s temperature Chlorofluorocarbons CFCs also destroy ozone in stratosphere which protects life from ultraviolet UV light Without UV absorption most plants and animals would die If stratospheric ozone were compressed to sea level pressure it would be a layer about 1 8 inch thick Ozone in stratosphere helpful to life by absorbing UV but harmful near surface when breathed main part of smog Ozone amount recovering Research published in 2006 http www sciencedaily com releases 2006 08 060830215811 htm 1 Jon Ahlquist Special Topic Breath of Fresh Air p 4 You are constantly breathing history Pick any historical person and key event in his or her life Examples shouting Eureka Caesar saying Veni vidi vici Cleopatra talking with Marc Anthony Martin Luther King Jr saying I have a dream 9 14 2006 Pressure pp 9 10 Archimedes Julius Record high surface pressure 1084 mb in Siberia 1968 only 7 above average Record low surface pressure 870 mb in Typhoon Tip 1979 14 below average Each breath you take may contain a molecule exhaled by that person at the chosen event Example of pressure calculation How much pressure does someone exert when lying on a bed Solution Pressure force area so consider someone who weighs about 150 lbs Area lying down 6 ft x 1ft 72x12 750 sq inches Therefore pressure in lying on a bed 150 750 1 5 lb per square inch which is very little Let s test this Air Pressure Decreases with Increasing Height Pressure force area Mean sea level pressure of air 15 lb sq in 30 inches of mercury 1013 millibars mb units used on TV for hurricanes 1013 hectopascals hPa metric system If the surface pressure changes by a few percent that is a BIG change Because of small changes in surface pressure pressure is measured to 5 digits of accuracy to tenth of millibar to follow weather changes Bed of nails This bed has 1 nail per sq inch By the calculation in the last graphic this is only 1 5 lb per nail which is no problem Density p 9 Air is held to the Earth by gravity i e it has weight Pressure at any given height is due to the weight of the air that lies above that height This is just like a human tower Pressure on one s shoulders depends on the weight above Person at the bottom experiences the greatest pressure Air at the surface experiences the greatest pressure and pressure decreases as you go up Density mass volume High density means lots of material mass in small volume Exponential decrease with height Density pressure atop Mount Everest are about 30 of sea level values Air density near surface about 1 kg m3 2 lb cubic yard Density liquid water density is 1000 kg m3 over 1700 lb cubic yard so liquid water is 1000 times denser than air p 10 fig 1 8 MET1010 Intro to the Atmosphere 2 Jon Ahlquist 9 14 2006 Why does density decrease with height Air like any gas is compressible That is you can squeeze it into a smaller volume making it denser At the surface where the pressure is greatest the compression is greatest so the density is greatest As pressure decreases going up compression decreases so density decreases Atmospheric layers p 11 fig 1 10 Layers Layers determined by temperature structure tops Hot top oxygen Thermosphere absorbs sunlight Mesopause 85 km Mesosphere Stratopause 50 km Stratosphere Tropopause 10 km Troposphere p 10 fig 1 8 TEMPERATURE Radiosonde Weather balloon p 14 fig 4 75 100 for balloon and instruments Launched 1 hour before midnight and noon Greenwich Mean Time now called UTC Instrument package hangs 85 below balloon measures temperature pressure relative humidity Has a radio transmitter Winds track balloon s radio Balloon pops over 15 mi up parachutes down Some are recovered Radiosonde launches by NWS at FSU Latex balloon inflated by tying it to nozzle in upper picture Helium used for safety instead of hydrogen Ceiling opened in inflation room to release balloon through cylinder in roof
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