Atmospheric Chemistry and Dynamics
Transcrição
Atmospheric Chemistry and Dynamics
Atmospheric Chemistry and Dynamics Condensed Course of the Universities of Cologne and Wuppertal in cooperation with the Institutes Stratosphere (IEK-7) und Troposphere (IEK-8) of the Forschungszentrums Jülich Prüfungsrelevanz Universität zu Köln - "Physik der Erde und der Atmosphäre" Für das Masterprogramm "Physik der Erde und der Atmosphäre" und dem "International Master of Environmental Sciences" der Universität zu Köln können 3 Kreditpunkte erworben werden. Der Leistungsnachweis erfolgt in einem Fachgespräch. Universität Wuppertal Der Kompaktkurs ist Bestandteil des "Schwerpunkts Atmosphärenphysik" im Rahmen des "Master-Studiengangs Physik" an der Bergischen Universität Wuppertal. Mit der Teilnahme können 5 Leistungspunkte erworben werden. Der Leistungsnachweis erfolgt in einem Fachgespräch. The Atmosphere NASA Atmosphere ~ 100 km Earth Radius 6370 km NASA Space Shuttle Endeavour Atmospheric Chemistry and Dynamics Schematic view of the components of the climate system, their processes and interactions. Gas Phase Composition of the Atmosphere % x 10-6 x 10-9 x 10-12 N2 O2 Ozone others Smoke from forest fires near Sydney (Dec. 2001) Aerosols = particles suspended in air Aerosol Concentrations Typical U.S. aerosol size distributions by volume URBAN RURAL Vertical Profiles of Pressure and Temperature Mesophere Stratopause Stratosphere Tropopause Troposphere Ideal Gas Law applicable to the atmosphere Assumption: gas is infinite compressible . R : universal gas constant in dry air : 287.05 J kg-1 K-1 Example: Pressure at ground : 1000 hPa, T = 280 K r = 1.244 kg m-3 stratosphere: 0.10 hPa, T = 230 K r = 0.015 kg m-3 Hydrostatic Equilibrium -- Barometric Height Equation Air Pressure Gravity Pressure change at infinitesimal change of height : Considering the ideal gas law: Integration yields the barometric height equation: scale height Scale Height RT h scale height H 7.4 km (T 250 K) Mag Scale height is not constant ! Real application must include the temperature gradient (lapse rate) : in the troposphere in the tropospause region in the stratosphere section above pb at the temperature Tb : with Atmospheric Mass (ma) m pb = ma g Radius of Earth: 6378 km Average Pressure at Ground: 984 hPa A 4 R PpSb 18 ma 5.2 10 kg g 2 Total mole number of air in the atmosphere ma Na 1.8 1020 moles Ma Molar Mass of Air Ma = 28.6 g/mol Mass Distribution of the Atmosphere 50 km Stratosphere ~ 18% air mass Troposphere ~ 82% air mass 12 km Temperature (K) Ground Solar Flux at the Top of the Atmosphere and at Ground ideal black body (T = 5900K) Intensity extraterrestrial solar spectrum Ozone terrestrial solar spectrum Water vapor CO2 Wavelength / nm http://de.wikipedia.org Vertical Distribution of Ozone in the Atmosphere Ozone Layer measured STRATOSPHERIC OZONE LAYER 1 “Dobson Unit (DU)” = 0.01 mm ozone at STP = 2.69x1016 molecules cm-2 THICKNESS OF OZONE LAYER IS MEASURED AS A COLUMN CONCENTRATION UV Absorption by Ozone UV-C 100-280 nm UV-B 280-320 nm UV-A 320-380 nm Solar Irradiance with Altitude biological damage Vertical Profile of Temperature and Water Vapour Saturation vapour pressure of liquid H2O Murray' s formula VERTICAL PROFILE OF TEMPERATURE Mean values for 30oN, March Radiative cooling Altitude, km - 3 K km-1 2 K km-1 Radiative heating: O3 + hn e O2 + O O + O2 + M e O3+M heat Radiative cooling - 6.5 K km-1 Latent heat release Surface heating Variations in Tropopause with Latitude Net Radiation Solar Radiation Modis Satellite Data: Surface Temperature Transport of Energy http://modis-atmos.gsfc.nasa.gov/ THE HADLEY CIRCULATION (1735): COLD Explains: • Intertropical Convergence Zone (ITCZ) • Wet tropics, dry poles HOT COLD Problem: does not account for Coriolis force. Meridional transport of air between Equator and poles would result in unstable longitudinal motion. Time Scales for Transport in the Troposphere 1-2 months 2 weeks 1-2 months 1 year TYPICAL TIME SCALES FOR VERTICAL MIXING in the troposphere • Estimate time Dt to travel Dz by analogy with molecular diffusion: 2 Dz Dt 2K z with K z = 5 10 cm s tropopause (10 km) 10 years 5 km “planetary 2 km boundary layer” 0 km 1 month 1 week 1 day 2 -1 Gobal Change of the Atmospheric Composition Development of Greenhouse Gases from IPCC 2007 Expected global temperature increase +1°C to +6°C until 2100 Stratospheric Ozone Depletion Atmospheric CFC Load Antarctic Ozone Hole Messungen Vorhersagen from WMO Report 2003 Total ozone column in October above Halley Bay after Jones & Shanklin, 1995 Increase of Tropospheric Ozone Tropospheric ozone is part of photochemical smog (toxic air pollutants) Parrish et al., 2008; Volz & Kley, 1988 Guangzhou in Pearl-River Delta, South China Extreme Air Pollution Megacities > 10 Mio Inhabitants Peak loads of pollutants encountered in summer: O3 100 - 150 ppb CO 1 – 5 ppm PM2.5 100 – 250 mg/m3