1. An Integrated View of North American Biosphere Carbon Flux Inter-annual Variability: from satellite CO2 to phenology
Junjie Liu1, Kevin Bowman1, Dave Schimel1, Nick Parazoo1, Anthony Bloom1, Meemong Lee1, Kevin Gurney2, Dimitris Menemenlis1
Jet Propulsion Lab, California Institute of Technology
Arizona State University
A-train Symposium
April, 2017
How A-train observatioins can help us understand the carbon cycle, here we focus on north American biospere

2. Global carbon cycle
Fossil fuel
photosynthesis
Atmospheric buildup
Global carbon cycle has four major components: one is fossil fuel emissions of CO2, it has been steadily increasing. In recent years, the emissions are around 10GtC/year. Another is the atmospheric carbon buildup, which is the amount of Fossil fuel emssions remained in the atmosphere, shown by the blue bar. ON areverage, about 50% fossil fuel emissions reamined in the atmosphere. The remaining fossil fuel has been absorbed by the either land through biosphere or ocean.
About 50% of fossil fuel emissions remained in the atmosphere
The land and ocean sink have large interannual variability
The net biosphere sink is the difference between gross primary production (GPP) and respiration

3. Focus of this study: North American Temperate
Fossil fuel (FF)
2011
2012
Atmospheric buildup ?
FF over North American Temperate
FF over the region is about 20% of the global FF
WE focus on North American temperate, which includes continental US, part of Canada and Mexico. Over this region, the FF emission is about 20% of global fossil fuel emissions.
Over this region, there were two major droiught events, 2011 over texas mesix and 2013
How much of this FF has been absorbed by biosphere over the region?
What is the interannual variability of this net biosphere flux?
What is the impact of drought events on net biosphere fluxes and carbon exchange processes?

4. Previous studies… -929±477 -890±400 -890±409 Unit: TgC/year
In-situ
King et al., 2015
North American biosphere flux from in-situ based flux inversion has about 50% uncertainty;
Many studies have tried to answer these questions. One of the methods is atmospheric inversion that infer surface fluxes based on atmospheric CO2 concentration observations. Using in-situ observatioins, which are about 100 around the globe, the inferred biosphere flux over North American has bout 50% uncertiaty in spite of relatively dense observations over the region.

5. Carbon Cycle Data Assimilation net biosphere exchange
Methodology
A-train OCO-2
Japanese GOSAT
2010
2011
2012
2013
2014
2015
Column CO2
Carbon Cycle Data Assimilation
(CMS-Flux)
In this study, we assimilated column CO2 observations from Ja carbon to constrain global net bisophere exchange over the globe
net biosphere exchange

6. Methodology MODIS Column CO2 Carbon Cycle Data Assimilation (CMS-Flux)
EVI
A-train OCO-2
Japanese GOSAT
2010
2011
2012
2013
2014
2015
Solar Induced Chlorophyll fluorescence (SIF)
Column CO2
Carbon Cycle Data Assimilation
(CMS-Flux)
To further understand the processes controlling biosphere exhange, we quantified GPP with SIF observations. MODIS, which is also on A-train, provide important phenology observations.
net biosphere exchange
Gross Primary Production (GPP)

7. Net biosphere carbon flux constrained by satellite CO2 observations
North American Temperate
GtC/year
Replot with magenta
Mean net biosphere sink is 1.2 ± 0.2 GtC with 0.2 GtC interannual variability

8. Biosphere, fossil fuel, and atmospheric buildup
North American Temperate
GtC/year
In this chart, year 2011 has weaker sink than the mean value, and much larger atmospheric build up. ?
2010
2015
Mean ( ) fossil fuel emission is 1.8 GtC; mean atmospheric build up is 0.6 GtC
Mean FF air borne fraction is 33% (ranging from 17% to 54%)

9. 2011 and 2012 drought impact on biosphere carbon fluxes

10. 2011 and 2012 precipitation anomaly
2011 precip anomaly
2012 precip anomaly
Texas-Mexico

11. 2011 drought impact
Replot the margin

12. 2011 drought impact
Precip
mm/day

13. 2011 drought impact
Precip
SIF-GPP
mm/day
MODIS-EVI

14. 2011 drought impact Fossil fuel Δ GPP (2011-2015) Δ NBE (2011-2015)
Relative to 2015, the 2011 Texas-Mexican drought reduced biosphere sink by 0.3±0.1 GtC, which is comparable to regional FF.

15. 2012 drought
Replot the margin

16. 2012 drought impact
Precip
mm/day
Lowest precipitation over the region

17. Net Biosphere Exchange
2012 drought impact
Precip
SIF-GPP
mm/day
MODIS-EVI
Net biosphere uptake is the lowest. While the annual GPP and EVI anomaly is not significant.
Why SIF-GG and MODIS EVI is not significant?
GtC/year
Net Biosphere Exchange
Lowes precipitation and smallest biosphere C sink in 2012;
Annual GPP and EVI anomaly are not significant

18. 2012 drought impact on seasonality
2010
2012
2015
EVI
SIF-GPP
Precip anomaly
2010
2012
2015
Why is not significant? We examined the seasonality of precipitation and temperate anoamaly 2012 black and blue are 2010 and 2015 respectively. At the begiinig of the year, it is featured with higher preciptation
T anomaly
Warmer and wetter at the beginning of the year=> higher EVI and GPP at the beginning
Drought peaked in June and July

19. Impact of 2012 drought impact
Fossil fuel
Δ GPP ( )
Δ NBE ( )
The net biosphere sink was reduced by 0.22±0.17 GtC which is 24% of regional FF emissions.

20. Impact of 2011 and 2012 drought
Fossil fuel
Δ GPP ( )
Δ NBE ( )
Both drought increased the FF air borne fraction; drought increased local FF air borne fraction by 100%, while 2012 drought increased local FF air borne fraction by 24%
2011 drought had larger impact on net biosphere carbon fluxes than 2012 drought

21. Conclusions
Synergistic use of A-train observations is critical to quantify and understand biosphere carbon flux interannual variability .
Mean FF air borne fraction over North American Temperate is 33%; with variability ranging from 17% to 54%
Drought events have large impact on regional FF air borne fraction.

22. Backup

23. Net biosphere exchange
Fossil fuel
Airborne Carbon
Bar is the standard deviation plus inter annual variability.

24. Precipitation anomaly
Seasonality
Net biome exchange
2010
2011
2015
Precipitation anomaly
EVI
Replot the seasonality between 2010 and 2011
T anomaly
SIF-GPP

25. Net flux difference between 2011 and 2010
Black: FLUXCOM
Green: top-down

26. Net biosphere flux difference between 2012 and 2010
Black: FLUXCOM
Red: top-down
While for the net biosphere fluxes
Increased uptake in April and reduced uptake in July, which are consistent with fluxnet upscaled FLUXCOM product

27. Methodology MODIS Column CO2 Carbon Cycle Data Assimilation (CMS-Flux)
A--Train
A-train OCO-2
Japanese GOSAT
2010
2011
2012
2013
2014
2015
500
MODIS
EVI
Solar Induced Chlorophyll fluorescence (SIF)
Column CO2
Carbon Cycle Data Assimilation
(CMS-Flux)
Upscaled FLUXNET fluxes
FLUXCOM
net biosphere exchange
Gross Primary Production (GPP)
Independent Evaluation