Simulating Atmospheric CO 2 for 2000: Our Quandary, Our Hypotheses and a Case Study Using Analyzed Climate, Transport and Satellite Vegetation Sheri L. Conner Gausepohl TRANSCOM Meeting June 2005 Paris, France

Introduction Research Goals Team: NASA/Goddard, CSU, NOAA-CMDL Oak Ridge Lab Models: SiB3 and PCTM Experiment Overview Our Quandary Our Hypotheses Case Study Next Steps

Goals Create a synthetic atmospheric [CO 2 ] product with realistic diurnal, synoptic and seasonal variations with quantified error –Sub-sampling for various observing systems –Testing inverse methods –Creating lateral boundary [CO 2 ] conditions for mesoscale models (SiB-RAMS) –Testing flux models and hypotheses of surface exchanges

Team NASA/Goddard –Randy Kawa –Steven Pawson –Jim Collatz –Zhengxin Zhu CSU –A. Scott Denning –Kevin Gurney –Ian Baker –John Kleist –Ravi Lokupitiya –Andrew Philpott –Lara Prihodko –Owen Leonard –Erin Chorak –Sheri Conner Gausepohl With many thanks to CMDL and Joe Berry and Steve Montzka NOAA - CMDL –Arlyn Andrews –Kevin Schaefer Oak Ridge Lab –David Erickson III

Parameterized Chemical Transport Model (PCTM) U U  U U 

PCTM – Previous Results Thanks to Kevin Gurney and Scott Denning PCTM TRANSCOM Responses CO 2 Concentration (ppm)

Simple Biosphere Model (SiB3) Thanks to Piers Sellers, Ian Baker et al.

Experiment Overview N D VI 10 year s 3 year s GEOS – 4 DAS Meteorology (core Goddard GCM) SiB3 Biosphere PCTM Transport (core Goddard GCM) IGBP Soils DeFries Biome Types Met Fields 1º x 1.25º x 55L x 3/6 hours Met Fields 1º x 1.25º x 3 hours NEE 1º x 1.25º x 1 hour 18 years 3 years NCEP Takahashi Ocean 1997 Andres Fossil Fuel Emissions 1990 [CO2] 2º x 2.5º x 25L x 1 hour ov/rrs/overview.ht m / faculty.law.lsu.edu/ccorcos/biblio/flask.gif

Quandary: Early Drawdown Hypotheses Autotrophic Respiration Photosynthesis: Normalized Difference Vegetation Index (NDVI) Radiation Case Study: COS Use carbonyl sulfide (COS) to quantify error in photosynthesis Data: red Model: green

Hypothesis: Respiration Heterotrophic Respiration –50% of annual Net Assimilation (GPP - Respiration leaf maintenance ) –Seasonality defined from Soil Temperature & Soil Moisture Autotrophic Respiration –50% of annual Net Assimilation –Seasonality defined by FPAR (canopy nitrogen) New Respiration Calculation: Thanks to Kevin Schaefer Temperate North America Old Scheme: red New Scheme blue CASA: green T3L3: black

Brief Note re: SiB3, CASA SiB3 FPAR estimated from mid-month linearly interpolated NDVI, BUT solar zenith angle dependent FPAR Single respiring carbon pool generates respiration that varies with soil temperature, soil moisture CASA FPAR estimated from mid-month linearly interpolated NDVI, BUT nadir FPAR Multiple respiring carbon pools generate respiration that varies with amount of material in labile pools, air temperature, soil moisture

Hypothesis: NDVI New NDVI Interpolation Schemes: Thanks to Andrew Philpott and the Tucker Group (NASA - Goddard) Data: green Old Scheme: Blue New Scheme: Red Assign maximum value composite NDVI values to: -day observed OR -first day, mid-point, last day of month based on curvature and linearly interpolate Tropics are an issue due to cloud contamination

Hypothesis: Radiation Separate treatment of sunlit and shaded leaves –Photosynthesis –Stomatal conductance –Leaf temperature –Transpiration Solar zenith angle dependence of canopy shading acts to delay onset of photosynthesis in new scheme Improved Canopy Radiation Scheme:

Case Study: Assessing Photosynthesis vs. Respiration Primary source: oxidation of marine organic matter Primary sink: terrestrial biosphere Large seasonal variation strongly related to CO 2 –Sink process identical to CO 2 in photosynthesizing plants –No source process akin to respiration from biosphere COS: the Sulfur Analog of CO 2 Thanks to CMDL for CO2 data and to Steve Montzka for COS data

Case Study: Assessing Photosynthesis vs. Respiration Estimate timescale of mixing between mixed layer and free troposphere from water vapor and CO 2 gradients Calculate COS drawdown using timescale and SiB3 Compare COS drawdown to observations of COS at WLEF COS: The Plan Free Troposphere Mixed Layer Canopy Air Space NOTE: SiB3 currently calculates all but one necessary resistance

Next Steps 1.Diagnose why SiB3-PCTM has springtime bias using COS (carbonyl sulfide) 2.(Improve SiB3 per results of diagnosis) 3.Run SiB3 with new schemes 4.Run PCTM at 1.0º x 1.25º resolution with updated fossil fuel and ocean fluxes 5.Calculate errors on [CO 2 ] using observations 6.Release hourly global [CO 2 ] product to science community with quantified errors

Thank you very much for your kind attention.