Cool Cities Clean Cities?

Transcription

1 Cool Cities Clean Cities? Secondary impacts of urban heat island mitigation strategies on urban air quality Joachim Fallmann, Renate Forkel, Stefan Emeis Institute of Meteorology and Climate Research (IMK-IFU) of the Karlsruhe Institute of Technology (KIT), Campus Alpine KIT University of the State of Baden-Wuerttemberg and National Laboratory of the Helmholtz Association

2 Heat stress in urban areas Heat stress days per year (greater Stuttgart area) < >35 Source: Klimaatlas Region Stuttgart 2 joachim.fallmann@kit.edu ICUC9 Toulouse

3 The Urban Heat Island UHI mitigation strategies? Urban Rural Effect on air quality? Source: Klimaatlas Region Stuttgart 3 joachim.fallmann@kit.edu ICUC9 Toulouse

4 Urban 1. Step: Modeling of the Urban Heat Island (WRF) 8 5'"E 9 '"E 9 1'"E 9 2'"E 9 3'"E 1 km 48 5'"N 48 5'"N 3 km 15 km 48 4'"N km 8 5'"E 9 '"E 9 1'"E 9 2'"E km km 9 3'"E 48 4'"N Corine Land Use Initial- und dynamical boundary conditions: ERA-Interim.5 Reanalysis Land surface processes: NOAH LSM Parametrization of sub-grid scale processes: BEP Urban Canopy Model Modelling time frame: Aug 8 Aug Evaluation: Fallmann et al joachim.fallmann@kit.edu ICUC9 Toulouse

5 Urban areas in mesoscale models Urban Parameter Urban Parameter Commercial High Density Low Density ZR: Roof level (building height) [ m ] SIGMA_ZED: Standard Deviation of roof height [ m ] ROOF_WIDTH: Roof (i.e., building) width [ m ] ROAD_WIDTH: road width [ m ] AH: Anthropogenic heat [ W m/m² ] FRC_URB: Fraction of the urban landscape which does not have natural vegetation [ Fraction ] Morphology CAPR: Heat capacity of roof [ J m³/ K ] 1.E+6 1.E+6 1.E+6 CAPB: Heat capacity of building wall [ J m³/ K ] 1.E+6 1.E+6 1.E+6 CAPG: Heat capacity of ground (road) [ J m³/ K ] 1.4E+6 1.4E+6 1.4E+6 AKSR: Thermal conductivity of roof [ J/ msk ] AKSB: Thermal conductivity of building wall [ J/ms K] AKSG: Thermal conductivity of ground (road) [ J /ms K ] ALBR: Surface albedo of roof [ fraction ] ALBB: Surface albedo of building wall [ fraction ] ALBG: Surface albedo of ground (road) [ fraction ] EPSR: Surface emissivity of roof [ - ] Street Parameters Building Heights EPSB: Surface emissivity of building wall [-] EPSG: Surface emissivity of ground (road) [ - ] Urban Category street direction street width building width height [m] [index] ZB: Roughness [geg length from for momentum, N] over [m] building wall [ m [m] ] Percentage.1 [%].1 Percentage [%].1Percentage [%] ZG: 33 Roughness length for momentum, over 19 ground (road) [ 25 m ] ZR: 33 Roughness length 9for momentum over 19roof [ m ] AKANDA_URBAN: Coefficient modifying the Kanda approach to computing surface layer exchange coefficient TBLEND: 31 Lower boundary 9 temperature for 18 building wall temperature 1 [ K ] TGLEND: Lower boundary temperature for ground (road) temperature [ K ] joachim.fallmann@kit.edu ICUC9 Toulouse Albedo

6 Simulation of UHI mitigation scenarios Control Many Parks Density Albedo Central Park T2 pot [ C] Aug pm Evaluation: Fallmann et al joachim.fallmann@kit.edu ICUC9 Toulouse

7 7 ICUC9 Toulouse

8 51 km Nord-Süd [grid cell] 2. Step: Air Quality modeling (WRF-Chem) WRF-Chem Domain 645 km 3km NO- Emissions (8 am) NO [mol km -2 h -1 ] West-Ost [grid cell] 18 Initial- and dynamical boundary conditions from global model MOZART (anthropogenic) und MEGAN (biogenic) RADM2 MADE/SORGAM chemical mechanism, MYJ PBL-scheme Lower boundary conditions MACC Emissions Modeled time frame: Aug 9 Aug Evaluation: Fallmann et al. 215 (In Review) 8 joachim.fallmann@kit.edu ICUC9 Toulouse

9 Effect of decreased temperature Primary pollutants (e.g. CO) Albedo-Control Park-Control Secondary pollutants (e.g. O3) Albedo-Control Park-Control? 9 joachim.fallmann@kit.edu ICUC9 Toulouse

10 Turbulence Primary pollutants(co, NO) Atmospheric dynamics Δ T [K] Control Albedo Park Mean diurnal cycle Scenario Control Albedo Park TKE [m -2 s -2 ] PBLH[m] joachim.fallmann@kit.edu ICUC9 Toulouse

11 Chemical reactivity Secondary pollutants (Ozone) Chemical reactivity Δ T [K] Control Albedo Park Mean diurnal cycle NO + O 3 NO 2 + O RADM boxmodel (Stockwell 1988) 11 joachim.fallmann@kit.edu ICUC9 Toulouse

12 Photolysis rate Secundary pollutants (Ozone) - Photolysis SW_UP [Wm-2] Control Albedo Park!? 12 joachim.fallmann@kit.edu ICUC9 Toulouse

13 Emission Quantification via tendency terms Impact of chemistry and dynamics on concentration of pollutants on the basis of hourly budgets (7-8 am) [ppb h -1 ] Tendency terms : chemical production/loss tendency (CHEM) Turbulent vertical mixing (TURB) Advection (ADV) Emission (EMIS) + Balance: Gain/Loss = EMIS + CHEM + TURB + ADV Turbulence - + Advection + Chemistry - 3 km CO 13 joachim.fallmann@kit.edu ICUC9 Toulouse

14 Case Study: Planting the wrong tree?! 1 More isoprene 14 h 15 h 16 h ΔISO [ppb] ? 2 more ozone?? ΔO3 [ppb] h 16 h 17 h joachim.fallmann@kit.edu ICUC9 Toulouse

15 Summary Urban Heat Island mitigation strategies? Surface reflectivity Urban greening Reduction of building density Feedback on urban air quality? Primary vs. Secondary pollutants Primary: Increase of CO and NOx Reduction of the temperature dependent turbulent mixing Dynamics dominate Secondary I: Reduction of ozone levels temperature dependency Secondary II: Increase of peak ozone concentrations for white roofs increased photolysis rates due to reflected UV 15 ICUC9 Toulouse

16 Merci Beaucoup? PHD-Thesis: Fallmann et al. 214 Erde Fallmann et al. 215 Atm Env (In Review) 16 ICUC9 Toulouse

17 [pptv h-1] [pptv h-1] [pptv h-1] Diurnal variation of tendency terms 3 2 CO 3 2 O TURB_Control TURB_Albedo -2 ADV_Control ADV_Albedo a) CHEM_Control CHEM_Albedo b) NO NO c) d) Time [hrs] Time [hrs] 17 joachim.fallmann@kit.edu ICUC9 Toulouse

18 Urban areas in mesoscale models 33: Industrial/ Commercial WRF Landuse 2 grid cells: 45 % Urban 32: High Density Residential Low Density Residental High Density Residential Industrial/Commercial 31: Low Density Residential 18 joachim.fallmann@kit.edu ICUC9 Toulouse

19 Model [ C] Model evaluation Point vs. Pixel Aug pm SLUCM BEP Tpot 2m [ C] T = 1.91 C T = 2.52 C R² =.76 R² =.65 R² =.58 BEP SLUCM Bulk Measurement [ C] 19 joachim.fallmann@kit.edu ICUC9 Toulouse

20 Reality Querschnitt White roofs durch das Stadtzentrum White roofs and walls Big Park Aug pm Stuttgart Central Station Source: Klimaatlas Region Stuttgart 2 joachim.fallmann@kit.edu ICUC9 Toulouse

21 Efficiency Albedo - Control Central Park - Control Density - Control Aug pm 2m potential air temperature [ C] 1 2 km (Fallmann et al. 214) 21 joachim.fallmann@kit.edu ICUC9 Toulouse

22 Model evaluation point vs. grid cell WRF-Chem grid cell Observation Mean over 3 Stations: Bad Cannstadt Schwabenzentrum Mitte Arnulf-Klett Platz 22 joachim.fallmann@kit.edu ICUC9 Toulouse

23 NOx [ppb] CO [ppb] Model evaluation point vs. grid cell O3 [ppb] Model OBS joachim.fallmann@kit.edu ICUC9 Toulouse

24 CO[ppt] O3 [ppt] NO [ppt] NO2 [ppt] Effect on near surface mixing ratios Mean concentration for modelling period Control Park Albedo ? 24 joachim.fallmann@kit.edu ICUC9 Toulouse

25 NOx-Cycle NO and NO2 NO + HO 2 NO 2 + OH NO + O 3 NO 2 + O 25 joachim.fallmann@kit.edu ICUC9 Toulouse

26 Parametrization of sub-grid scale processes Urban Canopy Model Z Log. wind profile Fluxes Radiation Sun Drag Wake diffusion Radiation Sun Roughness sublayer Lowest Level Urban Canopy Layer Roughness sublayer Urban Canopy Layer Lowest Model Level Single Layer Urban Canopy Model (Kusaka 21) Momentum Turbulence Heat Building Effect Parameterization (Martilli 22) Changed from Chen (211) 26 joachim.fallmann@kit.edu ICUC9 Toulouse

27 MACC Emission Inventory Quellstärken 27 joachim.fallmann@kit.edu ICUC9 Toulouse

28 concentration [ppb] The nitrogen cycle photochemical reactions + Advection and vertical transport from higher layers NO2 O3 NO Ox joachim.fallmann@kit.edu ICUC9 Toulouse

29 Biogene Emissionen als Vorläufer für Photosmog Photolyse bzw. Oxidation von VOC (B)VOC HCHO + hv H + HCO (HCHO + OH H 2 O + HCO) HCO + O 2 HO 2 + CO HO 2 + NO NO 2 + OH NO 2 + hv NO + O 3 29 joachim.fallmann@kit.edu ICUC9 Toulouse

30 VOC/NOx Ratio als Grundlage für Ozon-Produktion Kein VOC: Photo-Stationärer Zustand, keine Ozon- Bildung VOCs dazu: schnelle Photo- Oxidation (mit OH) Menge an O3 abhängig von Menge an VOC OFP = Gramm O3 pro Gramm VOC Ratio: VOC limitiert VOC/NOx < 4 Optimum für O3 Prod.: 15 < VOC/NOx < 4 NOx-limitiert VOC/NOx < 15 3 joachim.fallmann@kit.edu ICUC9 Toulouse

31 Tpot [ C] height [m] Urban Plume m 15 m 55 m 2 m Albedo Tpot [ C] m 33 m 55 m 2 m H max Urban Rural H mean Distance [km] 2 3 b) 4 T [ C] 5 Distance [km] 31 joachim.fallmann@kit.edu ICUC9 Toulouse

32 height [m] height [m] Querschnitt Vertikalgeschwindigkeit 12 - z-wind component [cms -1 ] Control Albedo Park Density distance [km] distance [km] 32 joachim.fallmann@kit.edu ICUC9 Toulouse