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Introduction to the Atmosphere. Prof. John Toohey-Morales, CCM St. Thomas University Miami Gardens, Florida. Earth’s Atmosphere. A thin gaseous envelope which extends up hundreds of kilometers (km) 99% lies within 30 km of the surface
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Introduction to the Atmosphere Prof. John Toohey-Morales, CCM St. Thomas University Miami Gardens, Florida
Earth’s Atmosphere • A thin gaseous envelope which extends up hundreds of kilometers (km) • 99% lies within 30 km of the surface • Shields us from the Sun’s dangerous ultra-violet (UV) rays as well as from inter-planetary debris
Water Vapor (H2O) • Varies greatly from place to place and time to time • Exists in all 3 states near the Earth’s surface • Water molecules are invisible in gaseous state, and become visible only in liquid or solid state
Water Vapor (continued) • Condensation: Water goes from gas to liquid • Evaporation: Water goes from liquid to gas • Water vapor is very important as it… • Provides Precipitation • Releases Latent Heat (source of energy) • Is a Greenhouse Gas, absorbing radiation
Carbon Dioxide (CO2) • Small but important component • Enters mainly from decaying vegetation &: • Exhalations of animal life, volcanic eruptions, burning of fossil fuels (coal, oil, natural gas) • Is removed by plants during photosynthesis • Entering faster than it’s being removed primarily because of the burning of fossil fuels & deforestation (rotting timber)
Global Warming • Prior to Industrial Revolution CO2 concentrations were stable at 280 ppm • As CO2 increases, so should average global surface temps • Warming from 2.5 to 10° F
Other Greenhouse Gases • Methane and Nitrous Oxide • Chlorofluorocarbons (CFC) concentrations had risen up until recently due to use as propellants in spray cans & refrigeration • CFCs can destroy Ozone (O3) which shields us from the Sun’s harmful rays • CFCs have caused an ozone hole to form
Aerosols and Pollutants • Aerosols mostly natural and beneficial • Dust, soil particles, salt, smoke, ash • Pollutants mostly man-made and a hazard • Carbon monoxide (CO), Nitrogen Oxide (NO2), Sulfur Dioxide (SO2), Hydrocarbons
Vertical Structure of the Atmosphere • Gravity holds air molecules near the Earth, compressing them together • Air density is greatest at the surface and decreases as we climb (first rapidly then slowly)
Vertical Structure of the Atmosphere (continued) • Air molecules have weight and exert a force called Air Pressure • As we climb the weight of the air above us decreases and pressure decreases
Air Pressure • Weight of a column of air 1 inch across is 14.7 pounds (PSI) • If more molecules are packed into this column, then density increases, therefore pressure increases (and vice versa) • More commonly we use millibars (mb), hecto-pascals (hPa), or inches of mercury (in. Hg) to measure barometric (air) pressure • Standard Atmosphere1013 mb = 1013 hPa = 29.92 in. Hg
Layers of the Atmosphere • Average lapse rate of 6.5°C per km or 3.6°F per 1,000 feet • The lapse rate fluctuates and temperature may even increase with height creating a temperature inversion
Troposphere • Surface to 11 km or Tropopause • Heated mainly from below • Contains all the weather • Stirred by vertical air currents
Other Layers • Stratosphere: Isothermal then a temp. inversion heated by O3 absorption of UV rays up to 20 km • Mesosphere: Air extremely thin, pressure quite low, and at -90°C is the coldest • Thermosphere: “Hot Layer” above where O2 molecules absorb energy from the Sun • Ionosphere: Not a layer, but an electrified region mostly within the Thermosphere with large number of ions and loose electrons
Meteorology • The study of the atmosphere and its phenomena • Dates back to Aristotle’s “Meteorologica” which presented the sum knowledge of weather and climate at the time • All substances that fell from the sky were meteors, hence meteorology • Young Science (read more on page 18)
Weather and Climate • Weather: The condition of the atmosphere at any one time and place (what we wear) • Weather Elements • Air Temperature, Air Pressure, Humidity, Clouds, Precipitation, Visibility, Winds • Climate: “Average Weather”, or the measurement of weather elements over a period of time, say years (what we buy)
