Using Simulated OCO Measurements for Assessing Terrestrial Carbon Pools in the Southern United States PI: Nick Younan Roger King, Surya Durbha, Fengxiang Han Zhiling Long, Jian Chen

 Estimated global total net flux of carbon from changes in land use increased from 503 Tg C (10 12 g) in 1850 to 2376 Tg C in 1991 and then declined to 2081 Tg C in  The global net flux during the period was 156 Pg C (10 15 g), about 63% of which was from the tropics.  The global total flux averaged 2.0 Pg C/yr during the 1980s and 2.2 Pg C/yr during the 1990s (but generally declining during that latter decade), dominated by fluxes from tropical deforestation.  The US estimated flux is a net source to the atmosphere of 7 Pg C for the period , but a net sink of 1.2 Pg C for the 1980s and 1.1 Pg C for the 1990s.  Hence, better estimates at regional level are required to understand and reduce the uncertainties in the sink/source estimations Introduction Data Source: Houghton, R.A, The annual net flux of carbon to the atmosphere from the changes in land use Tellus 51B:

Orbiting Carbon Observatory (OCO)  First global, space-based measurements of atmospheric carbon dioxide ( CO 2 ) with the precision, resolution, and coverage needed to characterize CO 2 sources and sinks on regional scales.  Uncertainties in the atmospheric CO 2 balance could be reduced substantially if data from the existing ground based CO 2 network were augmented by spatially resolved, global, measurements of the column integrated dry air mole fraction (X CO 2 ) with precisions of ~1 ppm (0.3% of 370 ppm) (Crisp et al 2004) Source:

Research Focus and Scope  This research is focused on the assessment of terrestrial carbon pools in the southeast and south-central United States.  In particular, this investigation intends to leverage upon:  Multiple NASA sensors  The terrestrial ecosystem model (CASA) and  Transport model GISS: GCM Model E  Undertake a Rapid Prototyping (RPC) experiment to address the need to quantify the carbon exchange over different ecosystems.  Test how well data from at model- grid resolution.  Test how well data from OCO observations and CO 2 measurement networks constrain CO 2 fluxes at model- grid resolution.

 What are the current annual rates of terrestrial carbon sequestration in each state of the region?  What's the overall contribution of terrestrial carbon sequestration in each state of the region to mitigating its total greenhouse gas emission?  What's the current baseline for possible carbon trading in the region?  What's the potential of further enhancing terrestrial carbon sequestration in the region?  What are the overall economic impacts of current and potential terrestrial carbon sequestration on the region? Currently funded DOE project for leverage

Carbon Recycling in the Future U.S. Bioenergy-Focused Agricultural Ecosystem. Total terrestrial carbon storage and pools in the Study Area

(i.e., sinks for C) Nutrient recycling in bioenergy-focused agricultural ecosystems. Square shapes indicate nutrient pools (i.e., sinks for C) in the bioenergy- agricultural ecosystem, while arrow shapes represent processes, such as decomposition/mineralization, ashing, evaporation, nitrification/denitrification, plant uptake, etc.

Annual fertilizer consumption in U.S. since the 1960s and the predicted fertilizers required by the proposed US bioenergy-focused agriculture in 2030.

Science Questions  Proposed RPC experiment seeks to address the following questions:  What information about carbon exchange can be obtained from OCO high-precision column measurements of ?  What information about carbon exchange can be obtained from OCO high-precision column measurements of CO 2 ?  How can we integrate top-down OCO measurements with ground based measurements, atmospheric and terrestrial ecosystem models to quantify carbon exchange over different ecosystems?  What are the current annual rates of terrestrial carbon sequestration in each state of the Southeast and South-central U.S.?  What is the current baseline in the region for possible carbon trading?  What is the potential for enhancing terrestrial carbon sequestration?

Rapid Prototyping Concept (RPC)

RPC Experimental Design Assimilation of aircraft measurements, satellite data (precipitable water, surface winds) Vegetation Indices Biome type Soil properties Weather Reanalysis Meteorology (e.g. GOES data analysis) 1 year spinup Monthly Terrestrial CO 2 surface flux Winds, cloud mass fluxes, model Parameters Forward Transport Model Fossil Fuels 1 year spinup (2002) Land Surface Model (CASA) Transport Model [CO 2 ] OBS OCO, Networks Inversion

RPC Experimental Design Vegetation Indices Biome type Soil properties Weather Reanalysis 1 year spinup Monthly Terrestrial CO 2 surface flux Land Surface Model (CASA) Assimilation of aircraft measurements, satellite data (precipitable water, surface winds) Meteorology (e.g. GOES data analysis) Winds, cloud mass fluxes, model Parameters Forward Transport Model Fossil Fuels 1 year spinup (2002) Transport Model [CO 2 ] OBS OCO, Networks Inversion

 NASA-CASA (Carnegie Ames Stanford Approach) model is designed to estimate monthly patterns in carbon fixation, plant biomass, nutrient allocation, litter fall, soil nutrient mineralization, and CO 2 exchange, including carbon emissions from soils world-wide.  Assimilates satellite NDVI data from the MODIS sensor into the NASA-CASA model to estimate  Spatial variability in monthly net primary production (NPP),  biomass accumulation,  and litter fall inputs to soil carbon pools NASA-CASA MODEL

NASA-CASA Model Tasks  Sensitivity analysis of how much NPP increase is required to sustain the regional terrestrial carbon sink of the study area.  Net Ecosystem Productivity (NEP) (defined as Net Primary Production (NPP) minus the heterotrophic soil respiration) predictions would be used to infer variability in regional scale carbon fluxes and to better understand patterns over terrestrial carbon sinks.  The NASA-CASA model estimates of carbon products would be calibrated with field-based measurements leveraged from DOE project of  Crop production,  Forest ecosystem fluxes, and  Inventory estimates of carbon pool sizes at multiple locations in south eastern and south central United States.

NASA-CASA Model Drivers (inputs) Air temperature (celsius) Solar radiation (w/m 2 averaged over each month) Deforestation Vegetation type Soil Types (SSURGO) Precipitation (PRISM)

NASA-CASA model outputs for Southern US (Note: Based on historical and 1987 data)

OCO Data Assimilation: Techniques and Strategies  Improved Kalman Smoother for atmospheric inversion.  Produces estimates of fluxes at a particular time using observations from that time step as well as observations from subsequent times.  Normal Kalman filter would use only past observations to estimate fluxes at a particular time step  Ensemble Kalman filters allows for application on large problem.  Adjoint-based descent methods for variational data assimilation  We are exploring the possibility of developing a Support Vector Regression-based technique for this purpose

Example Ensemble Based Assimilation Results (synthetic data)  The synthetic ground truth fluxes simulate one source area and one sink area.  The ensemble based technique was able to assimilate the observations to generate flux estimates with small errors. Observations Assimilation ResultsAssimilation Errors Ground Truth Fluxes source sink

RPC Experimental Design Assimilation of aircraft measurements, satellite data (precipitable water, surface winds) Vegetation Indices Biome type Soil properties Weather Reanalysis Meteorology (e.g. GOES data analysis) 1 year spinup Monthly Terrestrial CO 2 surface flux Winds, cloud mass fluxes, model Parameters Forward Transport Model Fossil Fuels 1 year spinup (2002) Land Surface Model (CASA) Transport Model [CO 2 ] OBS OCO, Networks Inversion

Design of Simulation Experiments  Simulated OCO data not available from NASA yet.  Currently use data generated on our own. Evaluation Transport Model Transport Model Ensemble Based Inversion Ensemble Based Inversion CASA Model CASA Model Perturbation With Errors Perturbation With Errors Simulated OCO Observations Surface Fluxes Simulated Priors Perturbation With Errors Perturbation With Errors Estimated Fluxes

 MODIS NDVI, SSURGO Soils, PRISM Precipitation datasets acquired and conditioned for Southern United States  Initial NASA-CASA model simulations completed and analysis of the model outputs is ongoing.  Assimilation algorithm coding is nearing completion.  Transport model simulations still in preliminary state, several issues regarding the coupling of NASA-CASA model and the transport model is under active research.  OSSE’s for OCO data is incomplete, looking for providers  Pursuing a OCO OSSE’s generation methodology published in a recent issue of Journal of Geophysical Research.  Asked to participate in 2008 Carbon Cycle and Ecosystems Joint Science Workshop to be held April 28 - May 2, 2008 Tasks Completed/Ongoing