Environmental Engineering Reference
In-Depth Information
NH4 concentration 2000 NL 10
SO4 concentration 2000 AT02
12
Measured
25
Modelled
10
Measured
Modelled
20
8
15
6
10
4
5
2
0
01/01/03
0
1.1. 1.2. 1.3. 1.4. 1.5. 1.6. 1.7. 1.8. 1.9. 1.10. 1.11. 1.12.
.
time (d)
01/04/03
01/07/03
01/10/03
01/10/04
time (d)
Fig. 1.
SILAM hourly predictions vs. measurement data from EMEP stations, 2000. Left-hand
panel: NO2 in air, Illmitz, Austria (AT02); Right-hand panel: NH4 in air, Vredepeel, The
Netherlands (NL10) [μg m
−3
].
Observations of sea salt, apart from dedicated experimental campaigns, are
available in three forms: (a) a few sites of the EMEP network performing regular
measurements of Na in aerosol (
Fig. 2,
left-hand panel); (b) several EMEP stations
perform ion analysis of precipitation including Na+ (
Fig. 2,
right-hand panel);
(c) satellite retrievals of aerosol optical depth in column (AOD) can be considered
representative for sea salt in remote regions of the southern hemisphere (Gong
et al., 1997, with care taken to distinguish sea salt AOD from that of e.g. biomass
burning plumes, Fig. 4). The model predicted the temporal variation fairly well,
but overestimates the concentrations by about a factor of 2 (on the annual average
level). The correlation of the predicted and measured hourly time series was ~0.50
on the average for all stations.
Sea salt concentration 2000 NO08
Sea salt wet deposition 2000 NO08
35
30
25
20
15
10
5
0
1000
Measured
Modelled
Measured
Modelled
800
600
400
200
0
1.1. 1.2. 1.3. 1.4. 1.5. 1.6. 1.7. 1.8. 1.9. 1.10.1.11.1.12.
1.1. 1.2. 1.3. 1.4. 1.5.
1.6.
1.7.
1.8. 1.9. 1.10. 1.11. 1.12.
time (d)
time (d)
Fig. 2.
SILAM hourly predictions vs. measurement data from EMEP stations, 2000. Left-hand
panel: Na+ in aerosol (μg m
−3
); right-hand panel Na+ wet deposition, Skreådalen, Norway
(NO08) (mg m
−2
day
−1
)
The global simulations were evaluated using the AOD observed by the MODIS
instrument onboard the NASA satellites Aqua and Terra. AOD is a column-
integrated optical parameter, which is more sensitive to number concentrations
than to the mass of aerosols; therefore AOD-based comparison is complementary
to the above analysis. This evaluation is only qualitative since we have not analysed
non-sea salt PM constituents
(Fig. 3)
.
