Atmospheric transport and chemistry lecture I III IV

Atmospheric transport and chemistry lecture I. III. IV. V. VII. V/ Introduction Fundamental concepts in atmospheric dynamics: Brewer-Dobson circulation and waves Radiative transfer, heating and vertical transport Stratospheric ozone chemistry The (tropical) tropopause Greenhouse gasses (GHG) and climate Solar (decadal) variability and dynamical coupling

Climate: energy in the sun-earth system Earth‘s radiation budget SW heating LW cooling UV/Vis/NIR Thermal IR Turco 1997 V/2

solar and terrestrial radiation Solar irradiance coming from the photospheric layer (Stefan-Boltzmann Law, Tsol=5800 K): Radiative power (units: Watt) the solar photosphere: Solar intensity at earth‘s radius: „solar constant“ V/

solar and terrestrial radiation (II) total solar intensity received on earth surface ( R 2 is only illuminated): earth Mean radiative flux density on the entire earth surface: radiation budget without atmosphere ènet radiative flux density (intensity) at surface èsuch a radiation budget can be set up at any altitude V/

Solar Insulation V/ Wallace & Hobbs 2005

solar and terrestrial radiation at earth‘s surface: solar radiation (UV/VIS) reflected back into space (a=0. 3 planetary albedo) thermal IR radiation emitted from surface Radiative equilibrium at the surface (F=0) V/

Climate without atmosphere without an atmosphere earth‘s mean surface temperature would be T=255 K=18°C. Atmosphere is responsible for thermal insulation and a global average surface temperature of T=288 K=+15°C. shortwave and long wave spectrum on earth‘s surface solar radiation is a black body with T=5800 K attenuated by a factor of 265000 represents 99% of shortwave emission (<4 m) terrestrial radiation is a black body with T=255 K and represents 99% of longwave emission (>4 m) SW V/ LW

SW and LW radiation from pole to pole V/ Wallace & Hobbs 2005

greenhouse gases: IR active gases Hanel et al. 1972 V/

simple climate model: the atmospheric green house effect Simple model: èatmosphere is approximated as an infinitely thin layer having a temperature of TA. It is transparent to shortwave radiation (UV/vis) but opaque to longwave radiation (IR) èsurface has a temperature of TB and reflects 30% (a=0. 3) of shortwave radiation back into space (albedo=0. 3). Like the atmosphere the surface is completely absorbing longwave radiation and acts like a blackbody with surface temperature TB. radiation budget (energy balance): V/

simple climate model: the green house effect TA=255 K corresponds to the mean temperature at 5. 5 km altitude (~500 h. Pa). This altitude divides the real atmospheric mass in about two halves. TB=303 K=30°C is about 15°C larger than the global mean surface temperature of 288 K. The heating of the atmosphere occurs because of IR absorption of H 2 O, CO 2, CH 4 etc. However, in a real atmosphere: è Some of the IR region is transparent (atmospheric window) è UV/vis region is not completely transparent mainly due to O 3, O 2, and H 2 O absorption è Clouds modify the planetary albedo (a=0. 6 -1. 0) Analogy to a real green house: è glas is 60% transparent to UV/vis radiation but much less transparent to IR è heat-up of the glas house is mainly due to convection (wind protection!). This is the major difference to the real atmosphere V/

atmospheric windows atmospheric window(s) Turco 1997 greenhouse gases in IR atmospheric windows V/

earth energy budget Turco 1997 V/

climate feedbacks: direct (radiation) and indirect Stratospheric aerosols (major volcanic eruption): èdirect effect: changes in albedo (scattering/cooling) and absorption (soot/warming) èIndirect effect: increases amount of CCN, more cloud can form Role of clouds: èCloud cover changes modify planetary albedo Chemical feedback èOzone depletion contrbutes to stratospheric cooling èWarmer troposphere leads to higher water vapor amounts, modifies clouds èMethane oxydation enhances stratospheric H 2 O (CH 4+OH CH 3+H 2 O), additional IR cooling èChemical response to temperature changes ècirculation changes (transport & chemistry) V/ Turco 1997

stratospheric aerosol V/

Stratospheric aerosol and temperature El Chichon Pinatubo ? Dhomse et al. , 2006 Impact of El-Chichon and Pinatubo èincrease in stratospheric temperatures in the tropics (increase of 2 -3 K @ 100 h. Pa for about 1 -2 years èincrease in H 2 O vapor (reduced freeze drying)? anti-correlation between Arctic and tropical LS temperature èaerosol effect on Brewer-Dobson circulation V/16

Trends in greenhouse gases (surface): CO 2 Note today: [CO 2] 382 ppmv [CH 4] 1800 ppbv Mouna Loa Hawaii Ahrens 1999 V/

Trends in greenhouse gases (surface) Note today: [CO 2] 370 ppmv [CH 4] 1800 ppbv IPCC 2001 V/

Current trends: CH 4 and CO 2 V/

GHG in the past fromice cores Note today: [CO 2] 370 ppmv [CH 4] 1700 ppbv 0 ky V/ 150 ky Age in kyears

Surface temperature trend NASA/GISS V/ Note: Year 2005 record warm year in NH

radiative forcing: greenhouse gases SROC IPCC V/

Forcing scenario (future prediction) Turco 1997 V/

Surface temperatures from the past to the future change in NH surface temperature until 2100 èfrom +1 K to +5. 5 K dependent on models Mann et al, 1998 Cubash V/ Mann et al. , 1998: temperature proxy data ECHO-G 1: climate model result

GHG sources & sink CO 2 CH 4 V/25 Major CH 4 sink: CH 4+OH CH 3+H 2 O CFC

Richter Buchwitz GHG space observation: local sources Green house gases (CH 4) and air pollution CO, SO 2, NO 2 V/26

Prediction of climate change cooling warming 2 x. CO 2 + GHG Schmidt, MPI-HH V/

Prediction of climate change July Temperature change from climate model due to doubling CO 2 and changes in SST (sea surface temperature) SST changes from a coupled ocean-atmosphere model with a 2 x. CO 2 atmosphere July doubling CO 2 only SST change + doubling CO 2 Changes in T èChanging reaction rates & heterogeneous chemistry V/ Schmidt, MPI-HH èChanging atmospheric circulation (transport)

Ozone and climate change stratospheric cooling leads to larger PSC volumes accumulated over winter Arctic CTM model results (solid: 2. 5° grid, light: 7. 5° grid) larger PSC volumes leads to higher observed heterogenous chemical ozone loss in Arctic winters high variability due to transport & chemistry (BD circulation) V/ Update Rex et al. 2004, Rex et al. 2006 Arctic

Current trends in GHG emissions „failure“ of Kyoto protocol „success“ of Montreal protocol and amendments V/ GWP: greenhouse gas warming potential (relative to CO 2)