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| Titel |
Columnar modelling of nucleation burst evolution in the convective boundary layer – first results from a feasibility study Part IV: A compilation of previous observations for valuation of simulation results from a columnar modelling study |
| VerfasserIn |
O. Hellmuth |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 6, no. 12 ; Nr. 6, no. 12 (2006-09-21), S.4253-4274 |
| Datensatznummer |
250004117
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| Publikation (Nr.) |
 copernicus.org/acp-6-4253-2006.pdf |
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| Zusammenfassung |
| In the preceding Papers I, II and III
a revised columnar high-order modelling
approach to model gas-aerosol-turbulence interactions in the convective
boundary layer (CBL) was proposed, and
simulation results of two synthetic nucleation scenarios (binary vs. ternary)
on new particle formation (NPF) in the anthropogenically influenced
CBL were presented and discussed. The purpose of the present finishing
Paper IV is twofold: Firstly, an attempt is made to compile
previous observational findings on NPF bursts in the CBL,
obtained from a number of field experiments. Secondly, the scenario
simulations discussed in Paper III
will be evaluated with respect to the
role of CBL turbulence in NPF burst evolution. It was
demonstrated, that completely different nucleation mechanisms
can lead to the occurrence of NPF bursts in the surface layer,
but the corresponding evolution patterns strongly differ
with respect to the origin, amplitude and phase of the NPF burst
as well as with respect
to the time-height evolution of turbulent vertical fluxes and
double correlation terms of physicochemical and
aerosoldynamical variables. The large differences
between the binary and ternary
case scenario indicate, that ammonia (NH3) can not be considered
as a time-independent tuning parameter in nucleation
modelling. Its contribution to the evolution of the NPF burst pattern is much
more complicated and reflects the influence of
CBL turbulence as well as the strong non-linearity
of the ternary nucleation rate. The impact of water (H2O) vapour
on the nucleation rate is quite varying
depending on the considered nucleation mechanism. According to the
classical theory of binary nucleation involving H2O and
sulphuric acid (H2SO4), H2O vapour favours NPF,
according to the classical theory of ternary nuncleation
involving H2O, H2SO4 and NH3
and according to organic nucleation via chemical reactions involving
stabilised Criegee intermediates (SCIs), H2O vapour disfavours nucleation,
and according to the parameterisation of
the collision-controlled binary nucleation rate proposed by Weber et al. (1996), H2O vapour does not explicitly affect
the particle formation. Since the H2SO4 concentration
is overpredicted in the
simulations presented in Paper III, the nucleation rates are too high
compared to previous estimations. Therefore, the results are
not directly comparable to measurements. Especially NPF events,
where organics are suspected to
play a key role, such as those observed
at the boreal forest station in Hyytiälä
(Southern Finland) or
at Hohenpeissenberg (mountain site in Southern Germany),
can not be explained by employing
simple sulphur/ammonia chemistry. However, some valuable hints
regarding the role of CBL turbulence
in NPF can be obtained. In the literature
a number of observations on the link
between turbulence and NPF can be found,
whose burst patterns support a strong contribution of
CBL turbulence to the NPF burst evolution simulated here. Observations,
that do not correspond to the scenarios
are discussed with respect to possible reasons for the
differences between model and observation. The model simulations
support some state-of-the-art hypotheses
on the contribution of CBL turbulence to NPF. Considering the
application of box models, the present study shows,
that CBL turbulence,
not explicitly considered in such models,
can strongly affect the spatio-temporal NPF burst evolution. The columnar
high-order model presented here is a
helpful tool to elucidate gas-aerosol-turbulence interactions,
especially the genesis of NPF bursts in the CBL. An advanced
description of the cluster formation and condensation growth
is required as well as
a comprehensive verification/validation study using observed
high-order moments. Further scenario simulations
remain to be performed. |
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