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

MEGAPOLI 212520
WP2: Megacity Environments: Features, Processes and Effects
Work package number 2 Start date or starting event: 1
Work package title Megacity Environments: Features, Processes and Effects
Activity Type 1 RTD
Participant number: 1 5 7 8 10 11 12 16 17
Person-months per participant: 7 11 5 4,4 8 10 2 3 12
Objectives
O2.1 To develop morphology/land-use/land-cover classifications and databases for megacities to be used in
meteorological, air quality and population exposure modelling.
O2.2 To develop sub-grid parameterisations of urban layer processes for megacity, regional and global scale models
Description of work and role of participants
Task 2.1: Surface morphology: classification and database (lead: FMI) surface characteristics for megacities and other
urban areas will be prepared a model-friendly format. Satellite imagery will be used to retrieve the form and dimension
of buildings and other structures. These determinations will take advantage of stereography, laser scanning and SARinterferometry.
Vegetation characteristics will be included in this.
Task 2.2: Flow deformation by urban canopy in the urban sub-layer (lead: DMI, UHel), small-scale features of urban
canopy and their direct effect on air flow will be analysed to improve parameterizations of the flow deformation and
inter-canopy transport processes. The work will aggregate urban canopy properties to identify a hierarchy of approaches
relevant to different urban and meteorological scales. A variety of single and multi-layer canopy approaches will be
used. CFD codes will be used to evaluate the urban canopy parameterizations of drag, dispersive stress and dispersive
fluxes. Vegetation will be considered included as roughness elements with more bluff bodies (buildings).
Task 2.3: Urban energy balance (lead: KCL, UHam) the atmosphere-surface exchange sub-models will be evaluated to
identify most realistic and physically grounded approaches applicable to urban surfaces in climate and air quality
models at a range of scales (addressed in different WPs). Participating modelling groups will be asked to provide their
surface models and/or to participate in their offline evaluation. On this basis the issues to be improved will be identified.
This task links with WP1 through inclusion of the anthropogenic heat flux and evaluation of its impact. Vegetation is
included as surface characteristic within these schemes that are to be used.
Task 2.4: Urban atmospheric boundary layer (UABL) (lead: NERSC, AUTH) essential physical processes for
parameterization of feedbacks between the surface morphology, the emission sources, urban climate and air quality will
be investigated. The simulated 3-D turbulence fields will be used to support the analysis and to improve
parameterizations of UABL in models addressing climate. An ensemble of LES codes will be employed to reduce
numerical uncertainties with the focus on Paris (the main target mega-city). Aggregation of LES data will allow more
accurate formulation for the UABL height in different stratification and roughness regimes, accounting for very strong
horizontal heterogeneity and anthropogenic heat flux (the features neglected in earlier approaches).
Task 2.5: Megacity dispersion features (lead: JRC, AUTH, NILU) emission and dispersion to the urban atmosphere of
passive and chemically reactive species will be analyzed; parameterizations of their effect in urban and regional scale
air quality models will be developed. Emissions are non-uniformly distributed in urban space at different heights.
Spatial variability in the intensity of individual sources is not typically considered as emission rates are normally
smoothed and gridded. Methods to parameterize the effect of horizontal and vertical variability of the surface emissions
will be investigated.
Deliverables
D2.1 Morphology database for a target megacity (month 18)
D2.2 Hierarchy of urban canopy parameterisations for different scale (LES, meso, and climate) models (month 18)
D2.3 Evaluation of surface flux balance modelling and urban features needed for climate and air quality models
(month 18)
D2.4 Urbanized turbulence-resolving model and evaluation against WP3 Paris plume data (month 36)
D2.5 Improved urban parameterizations based on prognostic equations, utilizing LES results (month 24)
D2.6 Evaluation of sub-grid models with interactions between turbulence and urban chemistry; recommendations
for emission inventories improvement (month 24)
D2.7 Improved parameterization of dispersion due to sub-grid heterogeneities in emission for different scale models
(LES, mesoscale, regional and global) (month 32)
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