The CO 2 budget: methods for estimating CO 2 fluxes from atmospheric observations. Jan Winderlich PhD student

Transcription

1 The CO 2 budget: methods for estimating CO 2 fluxes from atmospheric observations 1 Dr. Christoph Gerbig Research Scientist Jan Winderlich PhD student Dr. Rona Thompson Post-doctoral researcher

2 2 How do ecosystems and their biogeochemical cycles react to changes in climate, land use and biodiversity? Departments Biogeochemical Processes (Prof. Ernst-Detlef Schulze) Biogeochemical Systems (Prof. Martin Heimann) Independent Junior Research Groups Biogeochemical model-data integration (Markus Reichstein) Biospheric Theory and Modelling (Axel Kleidon) Organismic Biogeochemistry (Christian Wirth)

3 Outline 3 Motivation Introduction to carbon cycle CO 2 measurement Atmospheric models forward run inverse models

4 Motivation 4 Greenhouse gases raise since industrial revolution. climate impact Kyoto-Protocol: binding targets to reduce CO 2 emissions by 5% from 1990 to monitor countries actual emissions, emission trading possible Keeling curve breathing of the earth Understand natural feedbacks on CO 2 fluxes from climate variations Estimates of regional CO 2 fluxes needed

5 Carbon Cycle 5 [IPCC AR4 WG1 (Fig. 7.3), 2007] fluxes in GtC/yr (± 20%) - natural - anthropogenic gross fluxes huge but: net fluxes small

6 Carbon Cycle Human influence 6 CO 2 flux (Pg C y -1 ) Sink Source 1 GtC Carbon in above ground biomass in German forests [Global Forest Resources Assessment 2005 for UN FAO] Global Carbon Project (2008) fossil fuel emissions deforestation atmospheric CO 2 land ocean Time (y)

7 How to measure CO 2? 7 Global network of ground stations CO 2, CO 2 flux, CH 4, O 2 /N 2, CO, Tall towers (300 m) out of atmospheric surface layer Research / Commercial airplane profiles; follow air masses; network Satellite OCO, GOSAT

8 How to measure CO 2? 8 ratio: net / gross fluxes is small high accuracy needed Picarro Inc.: CO 2 /CH 4 analyzer using cavity ring-down spectroscopy

9 How to measure CO 2? 9 Picarro: Cavity Ring-Down Spectroscopy (CRDS): CO µm (std dev (5 sec.): 0.06 ppm 380 ppm in air high precision) Tunable Wavelength Photo- Laser Monitor Sample air Detector absorption spectrum Area ~ conc. CO 2, CH 4, H 2 O measurement tuned frequency (Δl cavity modes) τ ~ Absorption [ICOS workshop LSCE Nov 17_ Romanini.pdf]

10 CO 2 variability 10 Atmospheric measurements of the CO 2 mixing ratio in Bialystok: [Popa, 2007] Variability on diurnal, synoptic, seasonal and inter-annual timescales, caused by changes in atmospheric transport, vertical mixing and CO 2 fluxes

11 CO 2 variability 11 Comparison of continental (ZOTTO) and marine (Shetland) sites CO 2 measurement at ZOTTO 11/2005 to 05/ [E. Kozlova, 2008]

12 Regional models 12 Calculation of back trajectories result in footprint of measurement: Compare to simulated regional CO 2 field Model includes: VPRM (Vegetation Photosynthesis and Respiration Model) uses vegetation indices (MODIS satellite) vegetation synmap (several satellites) fossil emission (IER) global meteo data (ECMWF) weather forecast model (WRF) boundary conditions from global model Model: STILT-ECMWF Bialistok tall tower footprint

13 Regional model (forward run) 13 European near ground CO 2 (resolution: 1 h, 10 km): VPRM biospheric CO 2 fluxes WRF-VPRM CO 2 (-366 ppm) at 150 m [

14 Inverse model approach 14 a priori CO 2 fluxes (x,t) F O R W A R D R U N a posteriori CO 2 fluxes (x,t) y = K x + εy observed CO 2 (spacial + temporal) Jacobi-Matrix (change in conc. with norm. fluxes) Optimal flux estimation (Bayes Theorem): Transport model I N V E R S I O N Transport model unknown fluxes or parameter x $ ( 1 1 ) 1 ( 1 = K T S K T + S K S y + S 1 x ) prior ε prior CO 2 conc. (x,t) model result CO 2 (x,t) observation ε prior

15 Global CO 2 sources and sinks 15 Fossil Emissions + Land + Ocean ( ) Correction due to atmospheric measurements [Rödenbeck et al., 2003]

16 Challenges 16 accuracy of the atmospheric transport model measurements accuracy of CO 2 concentration a priori knowledge of the fluxes [Gerbig et al., 2008]

17 Summary 17 Motivation Keeling curve: breathing of the earth Introduction to C-cycle Human emissions: 9 GtC in 2008 CO 2 measurement Cavity Ring-down Spectroscopy Tunable Laser Wavelength Monitor Photo- Detector Atmospheric models for CO 2 flux estimations forward run inverse models

18 Thank you for your attention! 18 Acknowledgements BGC-staff, esp. Martin Heimann, Christoph Gerbig

19 Greenhouse gas emissions by sector 19 [EDGAR, 2000]