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Properties of the Atmosphere. Section 11.2. Temperature. Measured using one of two common scales (Fahrenheit or Celsius); based on the freezing and boiling points of water The SI unit for temperature is Kelvin; the zero point is absolute zero (the lowest temperature any substance can have)
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Properties of the Atmosphere Section 11.2
Temperature • Measured using one of two common scales (Fahrenheit or Celsius); based on the freezing and boiling points of water • The SI unit for temperature is Kelvin; the zero point is absolute zero (the lowest temperature any substance can have) • We discussed the changes in temperature throughout the atmosphere
Air Pressure • The pressure exerted on a surface by the weight of the atmosphere above Earth • Pressure = force / area • Units are N/m2 • Often measured in millibars (mb) • Air pressure decreases with altitude as the mass of air above you decreases
Air Pressure • The density of air decreases with altitude • Pressure, temperature, and density are all related in the atmosphere • At the same density warmer air is at a higher pressure than cooler air • At the same temp., air with higher density exerts more pressure than low density air • At the same pressure, warm air is less dense than cool air
Temperature Inversion • Temperature inversion – is an increase in temperature with height in an atmospheric layer • In the troposphere occurs with a rapid cooling of land on a cold, clear, calm winter night • Fog or low level clouds; increase pollutants in the air; Smog
Wind • In the lower atmosphere, air moves from high density regions to low density regions • Density differences are caused by unequal heating at Earth’s surface • Air moves from a region of high pressure to an area of low pressure • Wind speed is measured in (mph), (km/h), or knots. 1 knot = 1.85 km/h
Humidity • The amount of water vapor in the atmosphere at a given location on Earth’s surface • Relative humidity is the amount of water vapor in the air compared to the total amount it can hold; expressed as % • Saturation occurs when the water vapor in a volume of air has reached its maximum amount
Humidity • Dew point is the temperature at which air must be cooled at constant pressure to become saturated • Latent heat is the extra thermal energy contained in water vapor compared to liquid water • Adiabatic heating – air is compressed • Adiabatic cooling – air expands
Humidity • Dry adiabatic lapse rate – 10 oC / 1000 m • Moist Adiabatic lapse rate – 4 oC / 1000 m • Complete Problem Solving Lab on page 283 for a daily grade. Answer #’ 1-5.