Spurenstoffflussanalysen troposphärischer Feldexperimente mit chemischer 4D-var Datenassimilation
Tracer flux analyses of tropospheric field campaigns with chemical 4D-var data assimilation
Forecast - Database
CONTRACE
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SPURT
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AFOHAL
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VERTIKO
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| Current status (Oktober 2002) as presented at the AFO 2000 meeting at Schliersee. (html) |
| Current status (March 2004) as presented at the AFO 2000 meeting at Bad Tölz. (pdf - 400kB) |
The objective of the project is to provide thorough analyses of selected field experiments conducted in the AFO 2000 framework by an advanced spatio-temporal data assimilation procedure. To this end, the application of the first available four-dimensional variational (4D-var) chemistry data assimilation system is planned, where, by suitable choice of the pertinent mathematical method, an optimal combination of observations with an integrated chemistry-transport model (CTM) can be achieved. This approach results in a consistent chemical state analysis of the atmosphere, which is optimal in a predefined objective sense. Further, unobserved chemical species can be analysed, provided their chemical coupling with observed constituents is sufficiently strong. The University of Cologne mesoscale chemical transport model EURAD-CTM has been extended to an adjoint model version, which forms the kernel of the 4D-var algorithm. The CTM is used as a strong constraint, enforcing a fit as close as possible to the observations, while still giving a chemically consistent evolution of the simulated chemistry.
During the project duration four field campaigns funded by the
AFO 2000
program will be accompanied by simulations and provision of
assimilation products.
Prior to the availability of AFO 2000 field observations, a recent
measurement campaign
(BERLIOZ)
will be taken and reanalysed by variational assimilation, while
additional numerical and statistical features will be added to the
assimilation system. Assimilation system extensions, which will be
introduced in tandem with the progressing analyses of the case
studies, include 4D-var calculus with nesting, inhomogeneous
covariance statistics, chemical model adaptions with adjoint
components, and others. The four envisaged measurement campaigns
include two field experiments in the atmospheric boundary layer and
lower troposphere and two experiments at tropopause height levels,
including the lower stratosphere and upper troposphere. For the latter
case, the project "Tracer transport in the tropopause region"
(SPURT)
will infer fluxes of constituents to identify the relative
contributions of chemistry and transport processes. The project
"Convective transport of trace gases in the upper troposphere over
Europe: budget and impact on chemistry"
(CONTRACE)
aims at the analysis of vertical transport and chemical conversions of
polluted low level air masses after injection into the tropopause
height levels. In the planetary boundary layer the project
VERTIKO
will provide estimates of the vertical fluxes of ozone and ammonia. It
is further intended to assimilate data for a fourth field campaign
with observations of tropospheric halocarbons and to infer their role
in tropospheric chemistry.
After supplementing the data assimilation
system with special numerical model components required for each field
campaign, the project output will be high quality chemical state and
process analyses.
Rhenish Institute for Environmental Research (RIU) at the University of Cologne
Hendrik Elbern
Hendrik Elbern
Rheinisches Institut für Umweltforschung
Projekt EURAD
Aachener Straße 201-209
50931 Köln
This project is funded by:
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