Including the urban canopy layer in a Lagrangian particle dispersion - PowerPoint PPT Presentation

Including the urban canopy layer in a Lagrangian particle dispersion model Stefan Stöckl , Mathias W. Rotach, and Natascha Kljun

Project Overview FERUS F ootprint E stimation over R ough U rban S urfaces Figure: This Wikimedia Commons image is from the user Ramessos and is freely available under the creative commons cc-by-sa 3.0 license. ICUC10, Stöckl et al. 2018-08-06 1

Project Overview FERUS F ootprint E stimation over R ough U rban S urfaces dispersion model as “core” for footprint model more accurate dispersion model better footprint model Figure: This Wikimedia Commons image is from the user Ramessos and is freely available under the creative commons cc-by-sa 3.0 license. ICUC10, Stöckl et al. 2018-08-06 1

Why urban canopy layer height (log-scale) free troposphere z i Rotach et al. (1996) • non-urban planetary boundary layer outer or mixed layer • 3D in de Haan and Rotach (1998) 0.1 z i surface layer inertial sublayer Figure: adapted from Rotach and Calanca (2015) ICUC10, Stöckl et al. 2018-08-06 2

Why urban canopy layer height (log-scale) free troposphere z i Rotach (2001) • urban planetary boundary layer outer or mixed layer • Roughness Sublayer 0.1 z i • significantly improved surface layer inertial sublayer performance z * • has zero-plane roughness sublayer (RS) displacement d d Figure: adapted from Rotach and Calanca (2015) ICUC10, Stöckl et al. 2018-08-06 2

Why urban canopy layer height (log-scale) free troposphere z i Now • new urban canopy planetary boundary layer outer or mixed layer layer • zero-plane displacement no 0.1 z i longer required surface layer inertial sublayer • parameterizations z * of turbulence roughness sublayer (RS) profiles necessary z t urban canopy layer (UCL) Figure: adapted from Rotach and Calanca (2015) ICUC10, Stöckl et al. 2018-08-06 2

Lagrangian Particle Dispersion Model height distance • horizontally homogeneous (no topography) • stationary • unstable to neutral/stable • non-Gaussian and Gaussian PDFs • requires vertical profiles of u , u ′ w ′ , u ′ 2 , v ′ 2 , w ′ 2 , w ′ 3 , ε ICUC10, Stöckl et al. 2018-08-06 3

Roadmap Goal model down to ground (footprint sources there!) ICUC10, Stöckl et al. 2018-08-06 4

Roadmap Goal model down to ground (footprint sources there!) 1 find turbulence parameterization in the UCL 2 show model sensitivity to UCL-parameterizations 3 investigate changes in concentration output ICUC10, Stöckl et al. 2018-08-06 4

Problem • spatially heterogeneous • hard to measure • depends strongly on geometry • possible with LES/DNS/CFD: expensive (e.g. Auvinen et al., 2017) Figure: taken from Harman et al. (2016) ICUC10, Stöckl et al. 2018-08-06 5

Problem • spatially heterogeneous • hard to measure • depends strongly on geometry • possible with LES/DNS/CFD: expensive (e.g. Auvinen et al., 2017) Solution? spatial average Figure: taken from Harman et al. (2016) ICUC10, Stöckl et al. 2018-08-06 5

Data sets so far LES/DNS • part of London(Xie and Castro, 2009) • cubes(Coceal et al., 2007, 2006) ICUC10, Stöckl et al. 2018-08-06 6

Data sets so far LES/DNS • part of London(Xie and Castro, 2009) • cubes(Coceal et al., 2007, 2006) Wind Tunnel • “tombstone” canopy (Harman et al., 2016) • solid tree shapes (Böhm et al., 2013) • model of part of Nantes (France) (Kastner-Klein and Rotach, 2004) • model of part of London (Carpentieri et al., 2009) ICUC10, Stöckl et al. 2018-08-06 6

Data sets so far Field study LES/DNS • part of London(Xie and Castro, 2009) BUBBLE in Basel (Rotach et al., 2005) • cubes(Coceal et al., 2007, 2006) Wind Tunnel • “tombstone” canopy (Harman et al., 2016) • solid tree shapes (Böhm et al., 2013) • model of part of Nantes (France) (Kastner-Klein and Rotach, 2004) • model of part of London (Carpentieri et al., 2009) ICUC10, Stöckl et al. 2018-08-06 6

Data sets so far Field study LES/DNS • part of London(Xie and Castro, 2009) BUBBLE in Basel (Rotach et al., 2005) • cubes(Coceal et al., 2007, 2006) To do Wind Tunnel ETH Atmospheric Boundary • “tombstone” canopy (Harman et al., Layer wind tunnel, poster by 2016) Christina Tsalicoglou tomorrow • solid tree shapes (Böhm et al., 2013) • model of part of Nantes (France) (Kastner-Klein and Rotach, 2004) Suggestions welcome! • model of part of London (Carpentieri et al., 2009) ICUC10, Stöckl et al. 2018-08-06 6

Turbulence parameterization in UCL – example 4 . 0 Height scaling 3 . 5 • established that σ h important 3 . 0 • z/ ( z h + bσ h ) • b = 1 . 5 for now 2 . 5 z / ( z h + 1 . 5 σ h ) 2 . 0 1 . 5 1 . 0 0 . 5 0 . 0 − 2 . 0 − 1 . 5 − 1 . 0 − 0 . 5 0 . 0 0 . 5 u ′ w ′ / u 2 ∗ ICUC10, Stöckl et al. 2018-08-06 7

Turbulence parameterization in UCL – example 4 . 0 Old model 3 . 5 • stops at zero-plane displacement 3 . 0 2 . 5 z / ( z h + 1 . 5 σ h ) 2 . 0 1 . 5 1 . 0 0 . 5 0 . 0 − 2 . 0 − 1 . 5 − 1 . 0 − 0 . 5 0 . 0 0 . 5 u ′ w ′ / u 2 ∗ ICUC10, Stöckl et al. 2018-08-06 7

Turbulence parameterization in UCL – example 4 . 0 UCL parameterization 3 . 5 • use general function: u ′ w ′ UCL = b e az + c 3 . 0 • transition in height z t = z h + 1 . 5 σ h • continuous to profile from top: 2 . 5 z / ( z h + 1 . 5 σ h ) u ′ w ′ UCL ( z t ) = u ′ w ′ t 2 . 0 • boundary condition: u ′ w ′ (0) = u ′ w ′ 0 • free parameter (tuning): a 1 . 5 1 . 0 0 . 5 0 . 0 − 2 . 0 − 1 . 5 − 1 . 0 − 0 . 5 0 . 0 0 . 5 u ′ w ′ / u 2 ∗ ICUC10, Stöckl et al. 2018-08-06 7

Turbulence parameterization in UCL – example 4 . 0 UCL parameterization 3 . 5 • use general function: u ′ w ′ UCL = b e az + c 3 . 0 • transition in height z t = z h + 1 . 5 σ h • continuous to profile from top: 2 . 5 z / ( z h + 1 . 5 σ h ) u ′ w ′ UCL ( z t ) = u ′ w ′ t 2 . 0 • boundary condition: u ′ w ′ (0) = u ′ w ′ 0 • free parameter (tuning): a 1 . 5 1 . 0 Result (in black) u ′ w ′ UCL = u ′ w ′ 0 + u ′ w ′ t − u ′ w ′ 0 (e az − 1) 0 . 5 e az t 0 . 0 − 2 . 0 − 1 . 5 − 1 . 0 − 0 . 5 0 . 0 0 . 5 u ′ w ′ / u 2 ∗ ICUC10, Stöckl et al. 2018-08-06 7

Turbulence Profiles 4 z / ( z h + 1 . 5 σ h ) 3 2 Xie and Castro (2009) 1 Harman et al. (2016) B¨ ohm et al. (2013) 0 Coceal et al. (2006), staggered 0 2 4 − 2 − 1 0 − 1 . 0 − 0 . 5 0 . 0 Coceal et al. (2006), aligned u / u h u ′ w ′ / u 2 Sk w ∗ IS Coceal et al. (2006), square 4 Coceal et al. (2007) Kastner-Klein and Rotach (2004) z / ( z h + 1 . 5 σ h ) 3 BUBBLE U1 BUBBLE U2 2 Carpentieri et al. (2009) 1 0 0 20 40 0 20 40 0 5 10 15 u ′ 2 / u 2 v ′ 2 / u 2 w ′ 2 / u 2 ∗ L ∗ L ∗ L ICUC10, Stöckl et al. 2018-08-06 8

Turbulence Profiles 4 z / ( z h + 1 . 5 σ h ) 3 2 1 0 v1 0 2 4 − 2 − 1 0 − 1 . 0 − 0 . 5 0 . 0 v2 u / u h u ′ w ′ / u 2 Sk w ∗ IS v3 4 v4 default z / ( z h + 1 . 5 σ h ) 3 2 1 0 0 20 40 0 20 40 0 5 10 15 u ′ 2 / u 2 v ′ 2 / u 2 w ′ 2 / u 2 ∗ L ∗ L ∗ L ICUC10, Stöckl et al. 2018-08-06 8

Example comparison original model – model with UCL 105 grid positions concentration (ng m − 3 ) of model with UCL measurement positions 104 103 102 101 change in concentration due to 100 UCL: point moves up or down 10 − 1 10 − 2 10 − 3 10 − 4 10 − 4 10 − 3 10 − 2 10 − 1 100 101 102 103 104 105 concentration (ng m − 3 ) of original model ICUC10, Stöckl et al. 2018-08-06 9

Sensitivity of UCL parameterizations u ′ 2 v ′ 2 w ′ 2 w ′ 3 u ′ w ′ u v1 • hardly any sensitivity for u ′ w ′ v2 and w ′ 3 • variances u ′ 2 , v ′ 2 , w ′ 2 intermediate log concentration, sensitivity run v3 • highest or u v4 log concentration, default run ICUC10, Stöckl et al. 2018-08-06 10

Comparison with tracer experiments • compare measured and simulated concentrations (point to point) • all BUBBLE (Basel Urban Boundary Layer Experiment) field studies • selected MUST (Mock Urban Setting Test) field studies (Yee and Biltoft, 2004) ICUC10, Stöckl et al. 2018-08-06 11

Comparison with tracer experiments • compare measured and simulated concentrations (point to point) • all BUBBLE (Basel Urban Boundary Layer Experiment) field studies • selected MUST (Mock Urban Setting Test) field studies (Yee and Biltoft, 2004) Experiment FB NMSE CORR F2 original model 0.32 6.62 0.81 0.31 0.30 UCL included 6.67 0.80 0.27 FB ..........................fractional bias better values in bold NMSE ....normalized mean square error CORR ............. correlation coefficient F2 ............................factor of two ICUC10, Stöckl et al. 2018-08-06 11

Comparison with tracer experiments • compare measured and simulated concentrations (point to point) • all BUBBLE (Basel Urban Boundary Layer Experiment) field studies • selected MUST (Mock Urban Setting Test) field studies (Yee and Biltoft, 2004) Experiment FB NMSE CORR F2 original model 0.32 6.62 0.81 0.31 0.30 UCL included 6.67 0.80 0.27 • significance by bootstrapping • significantly better or worse at 95% level ICUC10, Stöckl et al. 2018-08-06 11