Estimation of daily CO 2 fluxes over Europe by inversion of atmospheric continuous data C. Carouge...
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Transcript of Estimation of daily CO 2 fluxes over Europe by inversion of atmospheric continuous data C. Carouge...
Estimation of daily CO2 fluxes over Europe by inversion of
atmospheric continuous data
C. Carouge and
P. Peylin ; P. Bousquet ; P. Ciais ; P. Rayner Laboratoire des Sciences du Climat et de l’Environnement
Acknowledgement : all experimentalists from Aerocarb project
high spatial resol. Modeldaily time step inversion
How to assimilate daily measurements ?
SchauinslandC
O2
(ppm
)
• Period : 1 year = 2001
• Observations : 10 European stations, daily averaged data
• Transport model : LMDZ, zoom over Europe
• Fluxes : - Europe & North east Atlantic : each pixel / daily
- Elsewhere : subcontinental regions / monthly
• Prior : Fluxes : optimised monthly fluxes
Errors : 1 GtC/year over Europe
0.5 GtC/year over north east Atlantic
tiny on other regions
• Correlations : spatial and temporal variable correlations between European pixels
Inversion setup
AEROCARB data base : http://www.aerocarb.cnrs-gif.fr/database.html
Continuous sites
Continuous European measurement sites
• Period : 1 year = 2001• Observations : 10 European stations, daily averaged data• Transport model : LMDZ, zoom over Europe • Fluxes : - Europe & North east Atlantic : each pixel / daily
- Elsewhere : subcontinental regions / monthly• Prior : Fluxes : optimised monthly fluxes
Errors : 1 GtC/year over Europe
0.5 GtC/year over north east Atlantic
tiny on other regions• Correlations : spatial and temporal variable correlations between European pixels
Inversion setup
Transport model
• Nudged on ECMWF winds• 192 x 146 and 19 vertical levels - 0.5 x 0.5 degrees in the zoom - 4 x 4 degrees at the lowest resolution
• Period : 1 year = 2001• Observations : 10 European stations, daily averaged data
• Transport model : LMDZ, zoom over Europe
• Fluxes : - Europe & North east Atlantic : each pixel / daily
- Elsewhere : subcontinental regions / monthly
• Prior : Fluxes : pre-optimised monthly fluxes
Errors : 1 GtC/year over Europe
0.5 GtC/year over north east Atlantic
tiny on other regions
• Correlations : spatial and temporal correlations between European / N.Atlantic pixels
Inversion setup
Spatial and temporal correlations
Based on correlation lengths :
L
jicedisjiCor
),( tan exp),(
Distance(i,j) : distance in space or time between 2 fluxes i, j
• L spatial : 500 - 800 km
• L temporal : 5 – 15 days
Technical aspects :
• Synthesis inversion to get posterior errors :
Sequential approach with overlap : 11 * 2 months inversions
Still 7000*60 unknowns covariance matrix of ~ 400,000 x 400,000 !!
• Use “retro-plume approach” (~ adjoint) to get daily response functions for all pixels
Huge memory size problems !
• Two steps inversion : - 1st : standard monthly Fluxes + Globalview data- 2nd : daily fluxes using the 1st step estimated fluxes..
FIRST RESULTS
( Still preliminary)
Two different inversions
• 10 sites : Cabauw tower at 120m and 200m • Data : full daily mean• Data-error : stdev of hourly measurements• Time correlation length : 5 days• Spatial correlation lengths : 500/800 Km for land/ocean
• 9 sites : Cabauw tower at 200 m
+ data-error x 3 in winter• Data : daytime-only mean• Time correlation : 15 days
First inversion
Updated inversion
Fit to the stations : WesterlandPosterior Prior
Observations + error bars
16/01 22/03 27/05 3/08 22/10 15/12(Days)
16/01 22/03 27/05 3/08 22/10 15/12
Fit to the stations : Monte CimonePosterior Prior
Observations + error bars
(Days)
Need to use different levels depending on the season
Aerocarb project : Forward simulation with REMOD model
“Proper” vertical level(appropriated
in winter)
Diurnal cycleAt
Monte-Cimone
Fit to the stations : SchauinslandPosterior Prior
Observations + error bars
16/01 22/03 27/05 3/08 22/10 15/12(Days)
Fit to the stations : Cabauw (200 m)Posterior Prior
Observations + error bars
16/01 22/03 27/05 3/08 22/10 15/12(Days)
May
November
Flux correction : posterior - prior
-250 -160 -70 20 110 200(gC / m2 / month)
First inversion Updated inversion
Total flux over Europefl
uxe
s (g
C/d
ay)
16/01 15/12(Days)30/0608/04 02/10
First inversion Updated inversion
30
25
20
15
10
5
0
16/01 22/03 27/05 3/08 22/10 15/12(Days)
Error ReductionE
rro
r R
ed
uc
tio
n (
%)
LAND OCEAN
First inversion
Updated inversion
Error Reduction for « small » regions
Posterior
-
Prior
(GtC/m²/month)
Error Reduction
(%)
Correlation = 2000 km
-25 0 50 100
0 6 18 3012 24
Impact of spatial correlation length
Correlation = 300 km
Conclusions …
• First daily inversion over a full year with real continuous data and flux error correlations !
• Spatial / Temporal patterns of fluxes critically depend on flux error correlations & error observations !
• Flux corrections are still a bit high…
… and Perspectives
• Comparaison with flux tower data / Bio. model
• Define spatial correlations from biogeochemical model
• Use improved prior fossil emissions
• Use new LMDz version with 38 vertical levels
• Integrated carbon assimilation system
Contributions
16/01 22/03 27/05 3/08 22/10 15/12(Days)
16/01 22/03 27/05 3/08 22/10 15/12(Days)
30
25
20
15
10
5
016/01 22/03 27/05 3/08 22/10 15/12(Days)
LAND OCEAN
Error reduction
(%)
Total fluxes and error reductionEuropean NEP North east Atlantic fluxPosterior fluxPrior flux
-20 1600 80gC/m²/month
Prior Fluxes