1. Earth Systems Science Chapter 4 PART I. THE CIRCULATION SYSTEM Convection and advection, the Ideal Gas Law Global energy distribution General circulation Winds Case study: Mar 2, 2004 Seasonal variability

2. CONVECTION Boyle’s law: Holding temperature constant: P i V i = P f V f Charles’s law: Holding pressure constant: V i / T i = V f / T f Ideal Gas Law: relationship between T, P, V under adiabatic conditions: PV = mRT P =  RT

3. CONVECTION Buoyancy: gravitational force causes less dense objects to rise above more dense fluids; more dense objects sink in less dense fluids Consider Ideal Gas Law, buoyancy, and heating of atmosphere near the earth’s surface, and you get convection

4. ADVECTION Three Main Forces that affect wind 1. Pressure Gradient Force 2. Coriolis Force 3. Friction

5. ADVECTION 1. Pressure Gradient Force Uneven heating at different places on the earth’s surface cause temperature differences  pressure differences Any object, or fluid, moves from high pressure to low pressure. So, Pressure differences  advection

6. ADVECTION 2. Coriolis Force Apparent force due to rotation on a sphere. Turns objects (air) to the right in the NH and left in the SH Depends on: latitude speed

7. ADVECTION 3. Friction Near the surface only Depends on type of surface (surface roughness) Affects the wind speed Is affected by the wind speed Affects wind direction through the coriolis force

8. ADVECTION: HIGH AND LOW PRESSURE SYSTEMS HL HL

9. GLOBAL ENERGY DISTRIBUTION

11. GENERAL CIRCULATION: TROPICS Convergence: Air streams moving towards one another within a vertical layer of the atmosphere or ocean Divergence: Air streams moving away from one another within a vertical layer of the atmosphere or ocean

12. GENERAL CIRCULATION: TROPICS ITCZ (low pressure) Subtropical Highs

13. GENERAL CIRCULATION: MID LATITUDES Polar Highs Low Pressure

14. WINDS: SURFACE High and low pressure cells develop along polar fronts

15. WINDS: UPPER LEVEL Warmer air  less dense  greater thickness Pressure decreases with height At any vertical level, pressure gradient is from equator  pole Winds are fastest where pressure gradient is greatest

16. WINDS: UPPER LEVEL Mean January 300 mb heights (decameters)

17. CASE STUDY: MARCH 2, 2004 850 mb 500 mb 300 mb 700 mb

18. CASE STUDY: MARCH 2, 2004

19. 4 day sequence 300 mb wind speed and height

24. CASE STUDY: MARCH 2, 2004 4 day sequence 850 mb temperature and height

29. CASE STUDY: MARCH 2, 2004 24-hr sequence of surface temperature and pressure

32. CASE STUDY: MARCH 2, 2004 48-hr sequence of satellite IR images

36. SEASONAL VARIABILITY Seasonal variability caused by obliquity (tilt) and revolution

37. Earth Systems Science Chapter 4 PART II. GLOBAL DISTRIBUTIONS OF TEMPERATURE AND RAINFALL Land – Ocean contrast Precipitation patterns The hydrologic cycle

38. LAND – OCEAN CONTRASTS Different heating rate of land/ocean surfaces results in different Temperatures, which results in a pressure gradient. Why do the land and oceans heat up at different rates? This affects the diurnal as well as seasonal temperature cycles.

39. GLOBAL TEMPERATURES: JAN MEAN

40. GLOBAL TEMPERATURES: JUL MEAN

41. GLOBAL TEMPERATURES: ANNUAL RANGE

42. GLOBAL PRESSURE DISTRIBUTION: JANUARY

43. GLOBAL PRESSURE DISTRIBUTION: JULY

45. MONSOONS

46. GLOBAL HYDROLOGIC CYCLE Water is a major pathway through which energy and materials are transported between the different components of the earth system. Energy: through latent heat of vaporization and latent heat of fusion, water transports energy between the different spheres. “LE” latent heat. Water vapor plays a role in the greenhouse effect Clouds play a role in the earth’s SW and LW energy budgets Materials: Water plays a role in weathering Water plays a role in transporting nutrients

47. GLOBAL HYDROLOGIC CYCLE

49. GLOBAL HYDROLOGIC CYCLE: LATENT HEAT

50. GLOBAL HYDROLOGIC CYCLE: CONDENSATION, EVAPORATION, SATURATION Condensation vapor to liquid Evaporation liquid to vapor Saturation: for every temperature, the maximum possible water vapor Condensation = evaporation Humidity: the amount of water vapor “relative humidity”: amount relative to the saturation level partial pressure

51. GLOBAL HYDROLOGIC CYCLE: WHEN DO WE GET CLOUDS AND/OR PRECIPITATION? cloud condensation nuclei surface on which water can condense uplift: convection frontal orographic convergence low pressure systems

52. GLOBAL HYDROLOGIC CYCLE: MEAN JAN PRECIPITATION

53. GLOBAL HYDROLOGIC CYCLE: MEAN JUL PRECIPITATION

55. GLOBAL HYDROLOGIC CYCLE: DESERTS