D E S C R I P T I O N O F W O R K - MEGAPOLI - Dmi

MEGAPOLI 212520
where large megacities are expected to develop and global warming is expected to have large
impacts.
This WP will take as a basis the fields of constituents calculated and analysed in WP5 and use these
within global and regional climate models to quantify the climate impacts. Additional studies will
use the same emission fields as in WP5, but simulate the constituent fields in interactive mode with
the climate and atmospheric composition evolving together. The constituent concentrations will
have been evaluated in WP5, but additional evaluation will take place in this WP to compare the
radiative forcings and aerosol optical properties against measurements. On both scales (global and
regional) the WP will focus on the climate effects from both direct aerosol/gas-radiation interaction
and indirect aerosol/gas-cloud interactions. WP6 will also provide meteorological driving fields for
future climate conditions to WP5. Finally, the climate impacts of well-mixed greenhouse gases
(e.g., CO2) emitted from megacities will be quantified using simple analytical formulae
(Ramaswamy et al., 2001).
WP7: Integrated Tools and Implementation
Overview and Background
Processes involving nonlinear interactions and feedbacks between emissions, chemistry and
meteorology require coherent and robust approaches using integrated/online methods. This is
particularly important where multiple spatial and temporal scales are involved with a complex
mixture of pollutants from large sources, as in the case of megacities. The impacts of megacities on
the atmospheric environment are tied directly to anthropogenic activities as sources of air pollution.
These impacts act on urban, regional and global scales. Currently, there are only limited attempts to
integrate this wide range of scales for regional and global air quality and climate applications.
Indeed, progress on scale and process interactions has been limited because of the tendency to focus
mainly on issues arising at specific scales. However the inter-relating factors between megacities
and their impacts on the environment rely on the whole range of scales and thus should be
considered within an integrated framework bringing together the treatment of emissions, chemistry
and meteorology in a consistent modelling approach. Numerical weather and air pollution
prediction models are now able to approach urban-scale resolution, as detailed input data are
becoming more often available. As a result the conventional concepts of down- (and up-) scaling for
air pollution prediction need revision along the lines of integration of multi-scale meteorological
and chemical transport models. MEGAPOLI aims at developing a comprehensive integrated
modelling framework usable by the research community which will be tested and implemented for a
range of megacities within Europe and across the world to increase our understanding of how large
urban areas and other hotspots affect air quality and climate on multiple scales.
Methodology and Advancement Beyond the State-of-the-Art
The integration strategy in MEGAPOLI will not be focused on any particular meteorological and/or
air pollution modelling system. The approach will consider an open integrated framework with
flexible architecture (module/interface structure) and with a possibility of incorporating different
meteorological and chemical transport models. Such a strategy will be made possible through
jointly agreed specifications to interface the modules for easy-to-use integration. The modules
which have to be considered, include input data such as emissions, meteorological and chemical
transport calculations. The structure of the framework will enable the coupling across the whole
range of scales by minimizing the scale-dependence of the interfaces. This multi-scale approach is
especially crucial for an efficient integration strategy. Indeed, atmospheric flows include frequently
locally forced features, which interact with regional- and global-scale processes such as fronts and
convection. Then, scale interaction is a challenge for both weather and air pollution predictions,
especially at regional scales. Depending on both time and space scales, certain atmospheric
23