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EOSC 112: THE FLUID EARTH

EOSC 112: THE FLUID EARTH. Atm12 Read: Kump et al. Chap.3, p. 44-45; Chap.4, p. 55-61. Objectives: To describe how atmospheric pressure and temperature vary with altitude; To explain why air moves; T o describe what sets the global atmosphere in motion ;

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EOSC 112: THE FLUID EARTH

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  1. EOSC 112: THE FLUID EARTH • Atm12 • Read: Kump et al. Chap.3, p. 44-45; Chap.4, p. 55-61. • Objectives: • To describe how atmospheric pressure and temperature vary with altitude; • To explain why air moves; • To describe what sets the global atmosphere in motion; • To describe the general pattern of Global Winds on a non-rotating planet. ATMOSPHERIC STRUCTURE AND DYNAMICS

  2. 1. Figures representing P change and T change with height

  3. Atmospheric pressure • Pressure = Force per unit area. • Pressure decreases exponentially with height. • 10 mbar (milliBar) = 1 kPa (kiloPascal)

  4. Atmospheric Temperature • Troposphere: ground to about 12km (16km in Tropics, 10km in Arctic) Unlike the other layers, it is subjected to constant vertical mixing (convection). It is this mixing process, through rising thermals and moist convection (followed by release of latent heat), that carries heat energy from the ground to cloud levels where it is radiated to space in the form of infrared radiation. • Stratosphere (12km to 50km) is a stratified layer of dry air. It contains most of the ozone.

  5. Topographic uplifting Frontal wedging Convergence Localized convection 2. Vertical Movement

  6. Mountain wave clouds & lee wave clouds

  7. Lenticular (lense-shaped) clouds (mountain wave clouds)

  8. Example: T inversion and Pollution • During night & early morning, clear sky => ground much cooler than air above => radiation (or surface) inversion • Inversion has warm air above cool air => very stable. Pollutants cannotdisperse upw. • Tall chimney goes • above inversion • layer => effective • dispersion • Daytime, ground warms => inversion disappears => pollutants disperse.

  9. Example: Inversionin valleys Night time: cool air drains downhill, settling into valleys. • Inversion at valley • Pollutants trapped in valley.

  10. 3. The driving Force

  11. Global Energy Distribution

  12. 4. Global winds – vertical and horizontal Horizontal movements: Temp. changes => Pressure changes => Winds H Rad L H H WARM Surface air warms

  13. Horizontal Motions: “7-step” development • Radiation absorbed by Earth’s surface– Surface warms • Air above ground warms by conduction – Air expands, density drops • Air becomes unstable – Convection sets in • Air rises – Pressure aloft increases • Air aloft pushed laterally away from warm surface – Surface pressure drops • Surface pressure around warm area increases – Air converges toward warm area • Air subsides around warm surface – Complete convection cell established

  14. Satellite view of the ITCZ

  15. Global winds on a non-rotating planet

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