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