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Physical Science

Physical Science. Introduction to Earth’s Atmosphere Slides subject to change. Air Density. Density ρ = Mass/Volume = m / V Air density at sea level: @ 68 °F, ρ = 0.00120 grams/cm 3 @ 95 °F , ρ = 0.00115 grams/cm 3 Warm air will rise, it is less dense. Air Pressure.

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Physical Science

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  1. Physical Science Introduction to Earth’s Atmosphere Slides subject to change

  2. Air Density • Density ρ= Mass/Volume = m/V • Air density at sea level: • @ 68°F,ρ= 0.00120 grams/cm3 • @ 95°F, ρ= 0.00115 grams/cm3 • Warm air will rise, it is less dense.

  3. Air Pressure • A column one square inch in cross-section measured from sea level to the top of the atmosphere would have a weight of about 14.7 lbs. • Therefore, pressure psealevel = 14.7 lbs/in2. • Higher elevations have lower pressures—Denver on average, 12.1 lbs/in2. • High winds also lead to lower pressures (Bernoulli’s Principle). 14.7 lbs

  4. Weather • Atmospheric conditions of troposphere called weather. • Above the troposphere, at 10-30 miles, is the stratosphere. • Ozone layer occurs ~15 miles. O + O2→ O3. Ozone absorbs most harmful wavelengths of ultraviolet radiation from the Sun, thus protecting life on the Earth.

  5. Concorde flew at this level

  6. Lapse Rate • Near Earth’s surface, in the troposphere, temperature normally decreases with increasing altitude. • Lapse rate = −3.5°F per 1,000 ft (up to 10 miles). • If the temperature is 80° at sea level, what is the temperature at 5,000 ft (Mt. Wilson)? • T = Tsealevel − (3.5)(altitude in thousands) • T = 80 − (3.5°F)(5) = 80 − 17.5 = 62.5 °F

  7. Solar Radiation • Radiation from the Sun heats Earth surface. • 67% absorbed by surface, 33% reflected.

  8. Smog • “Smoke and fog.” Cold Cold Cool Warm Warm Cool marine layer “Inversion Layer” No vertical circulation Normal Lapse Rate

  9. Air Motion, Sea Breezes • Air always moves from region of high pressure to region of low pressure. Rising warm air creates a low pressure area near the ground. Day Hot Land Cool water

  10. Prevailing westerlies and seabreezes. Where would you put wind turbines? Desert Hot air, rising Cold Water Cool air

  11. Santa Ana Winds If High Pressure “Nice weather” If Low Pressure “Stormy weather”

  12. Prevailing Winds Los Angeles Lat 39.9 ° Prevailing Westerlies

  13. Typical Weather Map Cold front

  14. Weather View NOAA Photo, infrared

  15. Flow of Weather In U.S., general air mass flow is from west to east, “westerlies”

  16. Columbus’s Path. Why? 30° N lat

  17. Storms Katrina 8/28/05 In northern hemisphere, storms rotate counterclockwise.

  18. Irene 8/27/11 Hurricane Irene rotated counterclockwise.

  19. Katrina Path. Why? 30 ° Latitude

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