chapter_04 - The Atmospheric The Atmospheric Circulation...

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Unformatted text preview: The Atmospheric The Atmospheric Circulation System Chapter 4 Dr. Emily Berndt Fundamentals of the Climate System EAS 253 I. Global Circulatory System I. Global Circulatory System a. The purpose of this chapter is to describe the major characteristics of the atmospheric circulation b. Organized movements occur over different time and space scales c. The functioning of Earth’s subsystems depends of different pumps i. i. ii. iii. iv. I. Global Circulatory System I. Global Circulatory System Short time scales (years to decades) Tropics Movement of air and surface ocean water Latent heat Energy source is the sun ii. Long time scales (~1000 years) 1. deep ocean currents 2. energy source is the sun 1. radioactive decay 2.source is earth’s interior heat 3. movement of continents iii. Longest time scales (millions of years) a. a. The Movement of Air II. The Atmospheric Circulation II. The Atmospheric Circulation Air moves because of horizontal difference in pressure Air moves vertically: Buoyancy (density differences) Mechanically forced Convection Convergence Frontal lifting Orographic lift b. a. b. a. b. c. d. c. Ultimately motions are caused by differences in temperature (except mechanical motions) Vertical Air Movement Vertical Air Movement Since pressure decreases with altitude: Adiabatic = no heat exchange Air molecules push parcel wall using their internal energy Rising parcel cools due to expansion (and sinking parcel warms due to compression) rising parcel expands sinking parcel contracts The cooling or heating rate is the adiabatic lapse rate Pressure and Temperature Pressure and Temperature Pressure relates to density; density relates temperature Colder air – molecules move more slowly and are closer together (more dense – column contracts) Warmer air – molecules move faster and are further apart (less dense – column expands) Horizontal Air Movement II. Atmospheric Circulation II. Atmospheric Circulation b. The Global Energy Distribution i. The average global temperature is determined by the balance between solar energy absorbed by the Earth and IR radiation emitted to space ii. Neither radiation from the sun or IR emission from Earth are uniform across the Earth II. Atmospheric Circulation II. Atmospheric Circulation b. The Global Energy Distribution iii. Poles should be getting colder and Tropics warmer. iv. Atmospheric temperature and density differences force atmospheric circulations ­differences in temperature differences in pressure… change in pressure air flow v. Weather and climate is the response of the atmosphere to the unequal energy distribution II. Atmospheric Circulation II. Atmospheric Circulation c. The General Circulation of the Atmosphere i. A negative feedback loop ii. The continuous addition of energy from the sun means the energy distribution is never balanced! Convergence, Divergence, and the Convergence, Divergence, and the Hadley Circulation The ITCZ The ITCZ The Polar Front The Polar Front Hadley Cell and Polar Front Hadley Cell and Polar Front II. Atmospheric Circulation II. Atmospheric Circulation d. The Coriolis Effect i. Coriolis effect creates E­W wind motions ii. Coriolis effect: the tendency of a fluid/ object to be deflected due to Earth’s rotation iii. Curve is the results of your frame of reference 1. right in northern hemisphere 2. left in southern hemisphere Factors Impacting Deflection Factors Impacting Deflection The amount of Coriolis deflection depends on: The rotation of earth The latitude The object’s speed Coriolis Effect Coriolis Effect Surface Surface Winds Upper Level Flow Upper Level Flow Horizontal Air Movement The Jet Stream The Jet Stream Geostrophic Wind Geostrophic Wind Seasons Seasons Seasonal Variability Seasonal Variability ...
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This note was uploaded on 04/11/2011 for the course EAS 253 taught by Professor Dr.emilyberndt during the Spring '11 term at Saint Louis.

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