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Fundamentals of air Pollution - Meteorology

Fundamentals of air Pollution - Meteorology. Yaacov Mamane Visiting Scientist NCR, Rome Dec 2006 - May 2007 CNR, Monterotondo, Italy. The Fog of London, Dec 5th , 1952 In early December 1952, an area of high pressure settled over London. Residents kept piling sulfur-rich coal into their

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Fundamentals of air Pollution - Meteorology

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  1. Fundamentals of air Pollution - Meteorology Yaacov Mamane Visiting Scientist NCR, Rome Dec 2006 - May 2007 CNR, Monterotondo, Italy

  2. Fundamentals of Air Pollution

  3. The Fog of London, Dec 5th , 1952 In early December 1952, an area of high pressure settled over London. Residents kept piling sulfur-rich coal into their stoves to keep warm in the near- freezing temperatures. In the still air, the smoke from these stoves and from coal-fired power plants in the city formed a smog laden with sulfur dioxide and soot. On Friday, 5 December, schools closed and transportation was disrupted. Fundamentals of Air Pollution

  4. Santiago in July Fundamentals of Air Pollution

  5. Dust storm in East Asia Fundamentals of Air Pollution

  6. Fundamentals of Air Pollution

  7. Fundamentals of Air Pollution

  8. Air Pollution System Fundamentals of Air Pollution

  9. Atmosphere • Structure • Composition • Energy balance for earth and atmosphere • Temperature in lower atmosphere and inversions Fundamentals of Air Pollution

  10. HOT COLD COLD THE HADLEY CIRCULATION (1735): Global Sea Breeze • Explains: • Intertropical Convergence Zone (ITCZ) • Wet tropics, dry poles • Problem: does not account for Coriolis force. Meridional transport of air between Equator and poles would result in unstable longitudinal motion. Fundamentals of Air Pollution

  11. GLOBAL CLOUD AND PRECIPITATION MAP20 Feb 2003 @12Z (Intellicast.Com) Fundamentals of Air Pollution

  12. Tropical Hadley Cell • Easterly “trade winds” in the tropics at low altitudes • Subtropical anticyclones at about 30o latitude Fundamentals of Air Pollution

  13. Climatological Surface Winds And Pressures (January)

  14. Climatological Surface Winds And Pressures(July) Fundamentals of Air Pollution

  15. Fundamentals of Air Pollution

  16. Characteristics of Troposphere and Stratosphere • Troposphere: • Ground level to 25 km. • Temp. normally decreases with altitude. • Strong vertical mixing. • Pollutants may be washed back to earth. • All weather and climate take place in the troposphere Fundamentals of Air Pollution

  17. Characteristics Of Troposphere And Stratosphere • Stratosphere: • 15-50 km • Temp. increases with altitude • Little vertical mixing, very slow diffusion exchange of gases with troposphere • Pollutants entering remain here unless attacked by light or other chemicals • Isolated from troposphere by tropopause Fundamentals of Air Pollution

  18. Half of air below 5.5 km Fundamentals of Air Pollution

  19. Stratification Of The Earth's Atmosphere Showing Changes In Temperature And Pressure With Altitude. Fundamentals of Air Pollution

  20. The Atmosphere Comments These ratios are the same through most of the atmospheric height. Total - is almost 99.99%. Where the pollution goes to ??? Typical atmosphere: N2 - 79%, O2 - 21% and MW - 28.85. Fundamentals of Air Pollution

  21. Minor Constituents Other constituents of the atmosphere include pollen, bacteria, fungi, particles (smoke, sea spray, dust), oxides of carbon, sulfur and nitrogen, and organic gases. Fundamentals of Air Pollution

  22. Blackbody Radiation Fundamentals of Air Pollution

  23. Planck’s law: Wien’s displacement law: [Kittel and Kroemer, 1980, p. 95] An Example of Temperature Dependence – Black Body • absorbs all incident radiation, emission is maximum • What is a black body? • What law from statistical mechanics describes the amount of radiation emitted by a black body? • What happens as T changes? Fundamentals of Air Pollution

  24. Radiative Equilibrium Slab Model of Earth • At top of atmosphere: • At surface: • To calculate- need to integrate Planck’s law over  Stefan-Boltzmann law: Fundamentals of Air Pollution

  25. Add the Atmosphere • In atmosphere: • At surface: BUT too hot for global mean temperature Fundamentals of Air Pollution

  26. Approximate the Atmosphere as a Grey Body • In atmosphere: • At surface: Kirkhoff’s law Fundamentals of Air Pollution

  27. Fundamentals of Air Pollution

  28. Fundamentals of Air Pollution

  29. Fundamentals of Air Pollution

  30. The Global Energy Budget •31% of the incoming solar radiation is reflected or scattered back to space – the ALBEDO •235 Wm-2 warms the Earth and atmosphere, 168 Wm-2 of which warms the surface. •235 Wm-2 corresponds to a black body temperature of -19 C, thermal emission at 10 um. •This is colder than Earth’s surface and is reached at around 5 km. •Thus the peak terrestrial emission is in the atmospheric window in the IR. •This fraction is transmitted directly to space, but majority is intercepted and interacts. •Clouds can absorb and emit thermal radiation but are also reflectors of solar radiation and so act to cool the surface. •Strong cancellation between these effects the global net effect appears to be a slight cooling at the surface. Fundamentals of Air Pollution

  31. The Atmospheric Oxygen Cycle. Fundamentals of Air Pollution

  32. stable Unstable Fundamentals of Air Pollution

  33. THERMAL INVERSION Fundamentals of Air Pollution

  34. Types of Thermal Inversions • Radiative: Earth cools during night by radiating thermal energy into space. In morning, air near surface will be cooler than air above creating thermal inversion. More frequent, but less problematic and persistent. • High pressure subsidence: high pressure mass of air moves towards earth. Is compressed and heated, causing thermal inversion some distance above ground. Fundamentals of Air Pollution

  35. Thermodynamics Gases Laws: In the Atmosphere there is no define volume of air and therefore it is advisable to use the parameter a instead. If a volume of air V has a mass M, then: R* =8.314107 erg/k*mol, and Ra=2.87106 erg/ gram ok Fundamentals of Air Pollution

  36. First Law of Thermodynamics: Heat is equivalent to energy, and both are conservative properties. Heat added = Internal heat + Work perform by the gas dW= Fdn = pAdn = pdV For per unit mass the Equation becomes: dq = du + dw dq = du + pd Fundamentals of Air Pollution

  37. dq = du + pd = Cv dT dq = CvdT = du dq = Cv dT+ pd Differential of p = RaT is pd + dp = RadT dq = CvdT + RadT- dp = CpdT - dp Fundamentals of Air Pollution

  38. For adiabatic case dq=0 Cp d T= dp Cp d T Cp d log T = Ra d log p Integration will yield: Ra=2.87 erg/ gram degree K Fundamentals of Air Pollution

  39. For adiabatic case Cp d T =  dp if we divide by dz (small vertical distance), we will get: Cp dT/dz = a dp/dz Or This is known as the Hydrostatic equation Fundamentals of Air Pollution

  40. From first Law of Thermodynamics for adiabatic case dq = du + dw = 0 Since Cp = 1.005 Cv = 0.716 Joule/gram*Degree K Fundamentals of Air Pollution

  41. Time Scales For Horizontal Transport(Troposphere) 1-2 months 2 weeks 1-2 months 1 year Fundamentals of Air Pollution

  42. Vertical Transport: Buoyancy What is buoyancy? z+Dz Object (r) Fluid (r’) z Note: Barometric law assumed a neutrally buoyant atmosphere with T = T’ T T’ would produce bouyant acceleration Fundamentals of Air Pollution

  43. Atmospheric Lapse Rate And Stability “Lapse rate” = -dT/dz Consider an air parcel at z lifted to z+dz and released. It cools upon lifting (expansion). Assuming lifting to be adiabatic, the cooling follows the adiabatic lapse rateG : z G = 9.8 K km-1 stable • What happens following release depends on the local lapse rate –dTATM/dz: • -dTATM/dz > Ge upward buoyancy amplifies initial perturbation: atmosphere is unstable • -dTATM/dz = Ge zero buoyancy does not alter perturbation: atmosphere is neutral • -dTATM/dz < Ge downward buoyancy relaxes initial perturbation: atmosphere is stable • dTATM/dz > 0 (“inversion”): very stable z unstable ATM (observed) inversion unstable T The stability of the atmosphere against vertical mixing is solely determined by its lapse rate Fundamentals of Air Pollution

  44. Effect Of Stability On Vertical Structure Fundamentals of Air Pollution

  45. What Determines The Lapse Rate Of The Atmosphere? • An atmosphere left to evolve adiabatically from an initial state would eventually tend to neutral conditions (-dT/dz = G ) at equilibrium • Solar heating of surface disrupts that equilibrium and produces an unstable atmosphere: z z z final G ATM G ATM initial G T T T Initial equilibrium state: - dT/dz = G Solar heating of surface: unstable atmosphere buoyant motions relax unstable atmosphere to –dT/dz = G Fundamentals of Air Pollution

  46. In Cloudy Air Parcel, Heat Release From H2o Condensation Modifies G z T Wet adiabatic lapse rate GW = 2-7 K km-1 RH 100% GW “Latent” heat release as H2O condenses GW = 2-7 K km-1 RH > 100%: Cloud forms G G = 9.8 K km-1 Fundamentals of Air Pollution

  47. VERTICAL PROFILE OF TEMPERATUREMean Values For 30on, March Radiative cooling (ch.7) - 3 K km-1 Altitude, km 2 K km-1 Radiative heating: O3 + hn e O2 + O O + O2 + M e O3+M heat Radiative cooling (ch.7) Latent heat release - 6.5 K km-1 Surface heating Fundamentals of Air Pollution

  48. Subsidence Inversion typically 1- 2 km altitude Fundamentals of Air Pollution

  49. Diurnal Cycle Of Surface Heating/Cooling: z Subsidence inversion MIDDAY 1 km Mixing depth NIGHT 0 MORNING T NIGHT MORNING AFTERNOON Fundamentals of Air Pollution

  50. Fronts WARM FRONT: WIND Front boundary; inversion WARM AIR COLD AIR COLD FRONT: WIND WARM AIR COLD AIR inversion Fundamentals of Air Pollution

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