ch4_pressure_wind1.ppt

Vertical structure of the atmosphere Review of last lecture Earth’s energy balance at the top of the atmosphere and at the surface. What percentage of solar energy is absorbed by the surface? Atmospheric influences on radiation (3 ways) The three types of atmospheric scattering. What causes the blue sky? Why causes the reddish-orange sunsets? What cause the greenhouse effect? What are the major greenhouse gases? Why is methane important? Sensible heat flux (dry flux from warm to cold regions) and latent heat flux (wet flux from wet to dry regions) Atmospheric Thickness No defined top to the atmosphere The atmosphere is very shallow—and is less than 2% of the Earth’s thickness Over 90% of atmosphere in the lowest 16km is where nearly all weather occurs Temperature Basics Temperature – measure of average kinetic energy (motion) of individual molecules in matter Different temperature scales: Kelvin, Celsius, Fahrenheit All scales are relative degrees F = 9?5 degrees C + 32 degrees K = degrees C + 273.15 Temperature Layers Longwave, Latent heat, Sensible heat Ultra-violet sunlight Solar winds, Cosmic rays An artist’s view Space shuttle Endeavour straddles mesosphere and stratosphere Video: Ionosphere Troposphere and Mesosphere /watch?v=EZuX1L1MD24 Pressure Essentials Pressure – force exerted/unit area (weight above you) units - Pascals (Pa) or millibars (mb) (1 mb = 100 Pa) Average surface pressure over globe: 1013.2 mb. Atmosphere is mixture of gases - partial pressure. Dalton’s Law: sum of partial pressures equals total pressure Pressure gradient (pressure difference between two locations/distance) gives rise to a force (pressure gradient force), which sets the air in motion. The Equation of State (Ideal Gas Law) Describes relationships between pressure, temperature, and density (Start w/ molecular movement in sealed container ? Pressure proportional to rate of collisions between molecules and walls). At constant temperatures, an increase in