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

MEGAPOLI 212520
WP6: Regional and global climate effects
Work package number 6 Start date or starting event: Month 1
Work package title Regional and global climate effects
Activity Type RTD
Participant number 1 3 9 15 21
Person-months per participant: 2 12 24 14 6
Objectives
O6 The overall objective is to quantify the effects of megacities on climate from the regional to the global scale by
using coupled and uncoupled global and regional chemistry-climate models and by analyzing observation data.
O6.1 To implement the fields of radiative forcing agents from WP5 into global and regional climate models (GCMs and
RCMs) in order to quantify the TOA and surface radiative forcing (direct and indirect) and related climate effects from
the WP5 scenarios.
O6.2 To calculate the effect of long-lived GHG (CO2, N2O, CH4, HCFC) megacity emissions on climate using simple
algorithms.
O6.3 To use satellite and ground-based measurements in order to assess the TOA radiative fluxes, surface aerosol
radiative forcing and AOD induced by megacities.
O6.4 To provide future-climate meteorological fields for use in other workpackages.
Description of work and role of participants
This work package will apply both regional and global-scale chemistry-climate models.
The regional models used will be RegCM3 (ICTP, CUNI) and Enviro-HIRHAM (DMI), at a horizontal resolution of
about 50 km. The global models to be used are UM (Met O) and ECHAM5/MESSy (MPIC), at a resolution of the order
of T63 (~1.9°). All include representations of gas and aerosol chemistry, and the direct and indirect effects of aerosols
are either already included or are currently being implemented via other projects.
Task 6.1: Regional and global radiative forcing and climate effects from constituent changes (lead: MetO, ICTP,
MPIC, DMI, CUNI)
The aerosol and ozone effects on climate due to emissions from megacities will be assessed using uncoupled and
coupled chemistry-climate models for present day and future emissions scenarios. In the uncoupled mode,
anthropogenic aerosol fields and ozone from WP5 for different emissions scenarios (with, without, and with
redistributed megacity emissions) will be implemented in the RCMs and GCMs. Where possible the fields will be
cross-implemented, i.e., each climate model will use fields from different models in WP5. Anthropogenic and natural
aerosols will be included. In the coupled mode, anthropogenic emission of aerosol precursors will be provided to the
chemistry-climate models and the aerosol fields will be calculated on-line for a subset of the most important runs. The
results from the two setups will be compared. Both direct and indirect aerosol effects will be considered, using state-ofthe-art
parameterisations for these processes. The top-of-atmosphere radiative direct and indirect forcings and related
climatic effects will be calculated online by the models. The analysis of climate effects will include the main
meteorological variables, the surface hydrological cycle, and cloud-radiation-aerosol interactions. The regional model
simulations will focus on the European region and one extra-European domain, either Asia or Central America. Three
sets of regional simulations are planned, each of 10-20 years length. In the first set, lateral meteorological boundary
conditions will be provided from analyses of observations (ERA40 or NCEP) and the simulation period will include the
special observing period planned in WP5. In the second and third sets, meteorological boundary conditions will be
taken from global model simulations of present day and future climate conditions, provided by the global GCMs in this
WP. Each set will include three simulations, one without aerosol effects (control run), and the others including aerosol
effects in uncoupled and coupled mode. Lateral chemical boundary conditions will be obtained from corresponding
global model simulations (WP5 and WP6).
Task 6.2: Radiative forcing and climate effects from long-lived greenhouse gases (lead: MetO).
As well as the effects of the short-lived constituents it is important to calculate the effect of the long-lived greenhouse
gases from megacities such as carbon dioxide and methane. As these gases will be well mixed, their radiative effects
will be calculated using the analytical formulae recommended in Ramaswamy et al. (2001) rather than full model
integrations.
Task 6.3: Measurements (lead: UHel)
Global distributions of aerosol optical parameters (spectral AOD and an indication of aerosol type) will be retrieved
from satellite observations using AATSR using the single view algorithm over the ocean (Veefkind et al., 1999) and the
dual view algorithm (Veefkind et al., 1998); Robles Gonzalez et al., 2000, 2006, 2007), for 1 year. The AATSR results
will be validated using AERONET measurements as well as lidar and in situ measurements of optical aerosol
parameters available through Infrastructure and Integrated Projects such as EUSAAR, EARLINET-ASOS, EUCAARI
and GEOMON, as well as available non-European networks. Satellite data from other sources may be used as needed
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