Publication Date:
2017-10-17
Description:
The concentrations of sulfate, black carbon (BC)
and other aerosols in the Arctic are characterized by high values
in late winter and spring (so-called Arctic Haze) and low
values in summer. Models have long been struggling to capture
this seasonality and especially the high concentrations
associated with Arctic Haze. In this study, we evaluate sulfate
and BC concentrations from eleven different models driven
with the same emission inventory against a comprehensive
pan-Arctic measurement data set over a time period of 2
years (2008–2009). The set of models consisted of one Lagrangian
particle dispersion model, four chemistry transport
models (CTMs), one atmospheric chemistry-weather forecast
model and five chemistry climate models (CCMs), of
which two were nudged to meteorological analyses and three
were running freely. The measurement data set consisted of
surface measurements of equivalent BC (eBC) from five stations
(Alert, Barrow, Pallas, Tiksi and Zeppelin), elemental
carbon (EC) from Station Nord and Alert and aircraft measurements
of refractory BC (rBC) from six different campaigns.
We find that the models generally captured the measured
eBC or rBC and sulfate concentrations quite well, compared
to previous comparisons. However, the aerosol seasonality
at the surface is still too weak in most models. Concentrations
of eBC and sulfate averaged over three surface
sites are underestimated in winter/spring in all but one model
(model means for January–March underestimated by 59 and
37% for BC and sulfate, respectively), whereas concentrations
in summer are overestimated in the model mean (by
88 and 44% for July–September), but with overestimates
as well as underestimates present in individual models. The
most pronounced eBC underestimates, not included in the
above multi-site average, are found for the station Tiksi in
Siberia where the measured annual mean eBC concentration
is 3 times higher than the average annual mean for all other
stations. This suggests an underestimate of BC sources in
Russia in the emission inventory used. Based on the campaign
data, biomass burning was identified as another cause
of the modeling problems. For sulfate, very large differences
were found in the model ensemble, with an apparent anticorrelation
between modeled surface concentrations and total
atmospheric columns. There is a strong correlation between
observed sulfate and eBC concentrations with consistent
sulfate/eBC slopes found for all Arctic stations, indicating
that the sources contributing to sulfate and BC are
similar throughout the Arctic and that the aerosols are internally
mixed and undergo similar removal. However, only
three models reproduced this finding, whereas sulfate and
BC are weakly correlated in the other models. Overall, no
class of models (e.g., CTMs, CCMs) performed better than
the others and differences are independent of model resolution.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
Permalink
