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S. Banzhaf et al.
26.1 Introduction
More than half of the world’s population lives in urban settlements. The rapid urbanization exacerbates the negative consequences and vulnerability of the urban climate
by replacement of the natural conditions, an excessive and concentrated consumption
of resources and a high energy demand resulting in increased air pollution. Accurate
representation of emission, dispersion, chemical transformation and removal of air
pollutants in the urban canopy requires fine-scale turbulence-resolving simulations
that can explicitly resolve building structures, surface heat fluxes at building facades,
street canyons and terrain variations.
LES models explicitly resolve relevant scales of turbulent motion, so that these
models can capture the inherent unsteadiness of atmospheric turbulence and advection. Nevertheless, LES models are so far rarely applied to urban air quality studies,
in particular for the investigation of chemical transformation of pollutants.
Within the joint project MOSAIK a new urban micro-scale model is developed
under the lead of the Institute of Meteorology and Climatology at the Leibniz Universität Hannover. The new urban micro-scale model PALM-4U is based on the
state-of-the-art LES model PALM [5]. PALM-4U includes a fully coupled ‘online’
chemistry module. In the following, the chemistry module is described and results
of a sample simulation are presented.
26.2 PALM-4U Chemistry Module
Chemistry is fully online coupled into PALM-4U. Automatic generation of the chemistry code with the Kinetic Pre-Processor (KPP, [1]) allows for high flexibility concerning the complexity of the applied chemical mechanism. A modified version of the
KP4 post-processor [3] is used for optimizing the KPP-generated code and adapting
it for PALM-4U.
Currently PALM-4U includes the following chemistry options:
• CBM4 (Carbon Bond Mechanism, Gery et al. [2], 32 compounds, 81 reactions)
• SMOG (a simple photochemical smog mechanism, 12 compounds, 12 reactions)
• SIMPLE (further simplification of SMOG, 9 compounds, 7 reactions)
• PHSTAT (photo-stationary state only, 3 compounds, 2 reactions)
• PASSIVE (just 2 passive tracers, no chemical reactions)
A simple photolysis parameterization is implemented in PALM-4U. So far shading
effects are not taken into account but will be implemented in near future.
Furthermore, a two-way LES-LES nesting is implemented in PALM-4U which
makes it possible to zoom in smaller areas (e.g. urban extracts of 1 × 1 km
2 ) for high
resolution simulation (of e.g. 1 × 1 m).
S. Banzhaf et al.
26.1 Introduction
More than half of the world’s population lives in urban settlements. The rapid urbanization exacerbates the negative consequences and vulnerability of the urban climate
by replacement of the natural conditions, an excessive and concentrated consumption
of resources and a high energy demand resulting in increased air pollution. Accurate
representation of emission, dispersion, chemical transformation and removal of air
pollutants in the urban canopy requires fine-scale turbulence-resolving simulations
that can explicitly resolve building structures, surface heat fluxes at building facades,
street canyons and terrain variations.
LES models explicitly resolve relevant scales of turbulent motion, so that these
models can capture the inherent unsteadiness of atmospheric turbulence and advection. Nevertheless, LES models are so far rarely applied to urban air quality studies,
in particular for the investigation of chemical transformation of pollutants.
Within the joint project MOSAIK a new urban micro-scale model is developed
under the lead of the Institute of Meteorology and Climatology at the Leibniz Universität Hannover. The new urban micro-scale model PALM-4U is based on the
state-of-the-art LES model PALM [5]. PALM-4U includes a fully coupled ‘online’
chemistry module. In the following, the chemistry module is described and results
of a sample simulation are presented.
26.2 PALM-4U Chemistry Module
Chemistry is fully online coupled into PALM-4U. Automatic generation of the chemistry code with the Kinetic Pre-Processor (KPP, [1]) allows for high flexibility concerning the complexity of the applied chemical mechanism. A modified version of the
KP4 post-processor [3] is used for optimizing the KPP-generated code and adapting
it for PALM-4U.
Currently PALM-4U includes the following chemistry options:
• CBM4 (Carbon Bond Mechanism, Gery et al. [2], 32 compounds, 81 reactions)
• SMOG (a simple photochemical smog mechanism, 12 compounds, 12 reactions)
• SIMPLE (further simplification of SMOG, 9 compounds, 7 reactions)
• PHSTAT (photo-stationary state only, 3 compounds, 2 reactions)
• PASSIVE (just 2 passive tracers, no chemical reactions)
A simple photolysis parameterization is implemented in PALM-4U. So far shading
effects are not taken into account but will be implemented in near future.
Furthermore, a two-way LES-LES nesting is implemented in PALM-4U which
makes it possible to zoom in smaller areas (e.g. urban extracts of 1 × 1 km
2 ) for high
resolution simulation (of e.g. 1 × 1 m).