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| Titel |
Introduction of the aerosol feedback process in the model BOLCHEM |
| VerfasserIn |
Felicita Russo, Alberto Maurizi, Massimo D'Isidoro, Francesco Tampieri |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039136
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| Zusammenfassung |
| The effect of aerosols on the climate is still one of the least understood processes in the
atmospheric science. The use of models to simulate the interaction between aerosols and
climate can help understanding the physical processes that rule this interaction and hopefully
predicting the future effects of anthropogenic aerosols on climate. In particular regional
models can help study the effect of aerosols on the atmospheric dynamics on a local scale. In
the work performed here we studied the feedback of aerosols in the radiative transfer
calculation using the regional model BOLCHEM. The coupled meteorology-chemistry
model BOLCHEM is based on the BOLAM meteorological model. The BOLAM
dynamics is based on hydrostatic primitive equations, with wind components u and
v, potential temperature θ, specific humidity q, surface pressure ps, as dependent
variables. The vertical coordinate Ï is terrain-following with variables distributed
on a non-uniformly spaced staggered Lorentz grid. In the standard configuration
of the model a collection of climatological aerosol optical depth values for each
aerosol species is used for the radiative transfer calculation. In the feedback exercise
presented here the aerosol optical depth was calculated starting from the modeled
aerosol concentrations using an approximate Mie formulation described by Evans and
Fournier (Evans, B.T.N. and G.R. Fournier, Applied Optics, 29, 1990). The calculation
was done separately for each species and aerosol size distribution. The refractive
indexes for the different species were taken from P. Stier’s work (P. Stier et al.,
Atmos. Chem. Phys., 5, 2005) and the aerosol extinction obtained by Mie calculation
were compared with the results reported by OPAC (M. Hess et al., Bull. Am. Met.
Soc., 79, 1998). Two model runs, with and without the aerosol feedback, were
performed to study the effects of the feedback on meteorological parameters. As
a first setup of the model runs we selected a domain over the Mediterranean sea
including the Italian peninsula. The initial and lateral boundary conditions used were
supplied by the European Centre for Medium-range Weather Forecasts (ECMWF)
analysis available at 0.5-Ã 0.5- resolution. The simulations were carried out for
August 1st 2003, during one of the warmest summers ever recorded in Europe. The
aerosol species that were considered for this feedback exercise were sulphates,
primary organic compounds and black carbon. For the remaining aerosol species the
climatological values were used. To study the effect of the aerosol feedback on
the meteorology we studied the variation of both the radiative flux at the surface
in the visible portion of the spectrum and the surface temperature. Preliminary
results show that the largest differences corresponded to the land portion of the
domain. In particular over the Po Valley region the application of the aerosol feedback
corresponded to a maximum decrease in radiative flux of 40W-m2. This difference in
radiative fluxes generated a maximum decrease in surface temperature of 0.4-K. These
values were in general agreement with the values found by Vogel B. et al (Vogel
B. et al, Atmos. Chem. Phys., 9, 2009) using the model system COSMO-ART. |
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