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Preparatory phase of the ENVISAT atmosphere chemistry mission validation
In
order to assess the impact of the assimilation, an experiment using simulated
observations has been set up. It is
carried out in 4 steps:
STEP
1 : Modelled state of the atmosphere
Ø
Free-running
simulation of the atmospheric model
STEP
2 : Simulation of the true state of the atmosphere
Ø
Obtained
by adding a white noise to the state vector at each time step
STEP
3 : Generation of the simulated measurements
Ø
From
the simulated true atmosphere and accounting for the instrumental characteristics
(geometry, sampling and precision of the instrument and of the retrieval).
STEP
4 - Assimilation run
Ø
the
independent assimilation of ENVISAT simulated measurements.
Preparatory phase of the ENVISAT atmosphere chemistry
mission validation
An
experiment using simulated observations (cont'd)
Team
ACRI-ST, (France)
Odile
Hembise, Antoine Mangin, Bertrand Théodore
the Service d'Aéronomie (S.A.), (France)
Alain
Hauchecorne, Jean-Loup Bertaux, Charlie
Cot
the Bologna University, (Italy)
*Massimo
Carlotti, Luca Magnani
the Bremen University, (Germany)
*Klaus
Bramstedt, Heinrich Bovensmann
the Finnish Meteorological Institute (FMI), (Finland)
*Erkki
Kyrölä, Seppo Hassinen
Preparatory
phase of the ENVISAT atmosphere chemistry mission validation
An
experiment using simulated observations (cont'd)
Generation of the simulated measurements
Instruments
observations characterisation:
·
Precision:
o
GOMOS
(vertical distribution of ozone concentration)
o
Precision
characterised with the stellar properties (Mv, T°)
o
MIPAS
(vertical distribution of ozone volume mixing ratio)
o
Precision
characterised with end-to-end simulations (instrumental + inversion)
o
SCIAMACHY
(total
ozone column)
o
Precision
characterised with end-to-end simulations (instrumental + inversion)
·
Geometry:
Location of the GOMOS/MIPAS/SCIAMACHY measurements
for 1 day.
Preparatory phase of the ENVISAT atmosphere chemistry
mission validation
RMS
after 3 days of MIPAS/GOMOS assimilation 
RMS
difference between the simulated true state and:
| Black: |
the
free running model; |
| Red: |
the
state after assimilation of GOMOS data; |
| Blue: |
the
state after assimilation of MIPAS data; |
| Green |
the
state after assimilation of MIPAS data with reduced error; |
| Orange: |
The
state after assimilation of biased MIPAS measurements. |
Clearly apparent is the gain (by a factor of 2) brought by the assimilation
above 100 hPa.
Ozone
fields (model, assimilated, true)
GOMOS
assimilation
after
3 days of assimilation (42.6 hPa)
 |
Model field |
| Assimilated field |
|
| True
ozone
field |
Ozone
fields (model, assimilated, true)
GOMOS assimilation
after 3 days of assimilation (27.6 hPa)
 |
Model field |
| Assimilated field |
|
| True
ozone
field |
Ozone
fields (model, assimilated, true)
GOMOS assimilation
after 3 days of assimilation (11.6 hPa)
 |
Model field |
| Assimilated field |
|
| True
ozone
field |
Ozone
fields (model, assimilated, true)
GOMOS assimilation
after 3 days of assimilation (4.85 hPa)
 |
Model field |
| Assimilated field |
|
| True
ozone
field |
Ozone
fields (model, assimilated, true)
MIPAS assimilation
after 3 days of assimilation (42.6 hPa)
 |
Model field |
| Assimilated field |
|
| True
ozone
field |
Ozone
fields (model, assimilated, true)
MIPAS assimilation
after 3 days of assimilation (27.6 hPa)
 |
Model field |
| Assimilated field |
|
| True
ozone
field |
Ozone
fields (model, assimilated, true)
MIPAS assimilation
after 3 days of assimilation (11.6 hPa)
 |
Model field |
| Assimilated field |
|
| True
ozone
field |
Ozone
fields (model, assimilated, true)
MIPAS assimilation
after 3 days of assimilation (4.85 hPa)
 |
Model field |
| Assimilated field |
|
| True
ozone
field |