Operational Dust Prediction - Mineral Dust: A Key Player in the Earth System - page 235

10.2.2 Regional Models

CHIMERE Model

The CHIMERE model is dedicated to the transport and chemistry of numerous
gaseous and aerosols species. It has been in development for more than 15 years
and is intended to be a modular framework available for community use. The
dust emission fluxes take into account physical processes such as saltation and
sandblasting. A complete description of the dust calculation is presented in Menut
et al. ( 2007 ). For long-range transport simulations, the model domain includes
Africa and Europe requiring a coarse horizontal grid spacing of 1

1 ı .Inorderto
take into account the subgrid-scale variability of winds, dust emissions are estimated
using a Weibull distribution for the wind speed (Menut 2008 ). In Menut et al. ( 2009 ),
an intensive observation period of the African Monsoon Multidisciplinary Analysis
(AMMA) programme was modelled in forecast mode to study the variability of
modelled surface dust concentrations. It was shown that most of this variability
comes from model uncertainties in emissions, transport and deposition as well as
from variations in the meteorological fields (see Fig. 10.1 ).

CUACE/Dust

CUACE/Dust is an integrated atmospheric chemistry modelling system applied for
dust (see special issue at http://www.atmos-chem-phys.net/special_issue81.html ) ,
which has been operationally run for dust forecasts in China Meteorological Admin-
istration (CMA) since 2004 and for the WMO SDS-WAS Asia Node-Regional
Centre since 2007. CUACE has been designed as a unified chemistry module to
be easily coupled with atmospheric models through a common interface. Its aerosol
module utilises a size-segregated multi-component algorithm for different types of
aerosols including dust, sea salt, black and organic carbon, nitrate and sulphate
(Gong et al. 2003a ; Zhou et al. 2008 , 2012 ). A detailed desert distribution with
soil texture data base and dust particle-size distributions measurements from nine
major deserts for China was adopted (Gong et al. 2003b ; Zhang et al. 2003 ).
One of the unique features of the CUACE/Dust is the implementation of a 3D-
Var data assimilation system using both satellite and surface observations in near
real-time to improve the initial conditions and hence the forecast results (Niu et al.
2008 ). A scoring system has been developed where observations from various
sources concerning dust aerosol, i.e. surface observations of sand and dust storms
and satellite retrieved Infrared Difference Dust Index (IDDI; Hu et al. 2008 ), are
integrated into a geographic information system (Wang et al. 2008 ).