Environmental Engineering Reference
In-Depth Information
At city scale, the development of the urban Paris ozone plume was studied
during the ESQUIF field campaign (Menut et al., 2001) that has taken place
during three consecutive summer periods (1998-2000). The use of CHIMERE and
the campaign measurements allowed to identify the areas around Paris most
exposed to ozone pollution and the sensitivity to emissions (Sillman et al., 2003;
Beekmann and Derognat, 2003).
The description of patterns of pollutant concentrations also progressed con-
cerning mineral dust due to Aeolian erosion. A “dust” version of the CHIMERE
model has been developed (Menut et al., 2009), that was able to describe several
episodes of mineral aerosol elevated concentrations (see, e.g. Bessagnet et al.,
2008).
2. Synergetic Use of Oservations with Model Simulations
A major progress in the use of observations and model simulations in synergy is
the development of methods for spatial representation of air quality pollutant
concentrations. The deal is that surface observations are more accurate than model
simulations but model simulations cover areas uncovered by observations. Several
advanced methods have been devised such as four-dimensional variationnal
assimilation (Elbern and Schmidt, 2001). At IPSL a geostatistical approach has
been developed, tested over several real cases (Blond et al., 2003), and used in
operational real-time ozone and PM10 analyses within the PREV'AIR system
(Honoré et al., 2008).
Data assimilation of satellite data may also help describing the three-dimensional
structure of the regional atmospheric composition. For instance an ensemble Kalman
filter approach has been tested in idealized experiments conducted to evaluate the
added value of satellite data to PM2.5 forecasts (Timmermans et al., 2009). These
applications are presently preliminary. However, a general result that was found in
other studies was confirmed: air quality forecasts are weakly sensitive to initial
conditions beyond a lead time of about 24 h (Elbern and Schmidt, 2001; Blond
and Vautard, 2004; Timmermans et al., 2009).
Another important use of models and data has been demonstrated in several
attempts to improve emission inventories by the use of observations. Results are
often difficult to interpret because of the bad handling of model errors. However
striking reliable results were obtained by the synergetic use of CHIMERE decadal
simulations and satellite observations of NO
2
columns from the GOME and
SCIAMACHY platforms (Konovalov et al., 2008). This study showed in particular
European regions where observed NO
2
column decadal changes are compatible with
emission inventories as provided by countries.
