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FLUXNET: Integrating Global Flux Measurements

FLUXNET: Integrating Global Flux Measurements. Dick Olson, Bob Cook, Susan Holladay, Les Hook ORNL DAAC January 2001 NASA EOS Validation Program NASA EOSDIS DAAC. FLUXNET Overview. Data being collected

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FLUXNET: Integrating Global Flux Measurements

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  1. FLUXNET: Integrating Global Flux Measurements Dick Olson, Bob Cook, Susan Holladay, Les Hook ORNL DAAC January 2001 NASA EOS Validation Program NASA EOSDIS DAAC

  2. FLUXNET Overview • Data being collected • carbon, water vapor, and energy fluxes using eddy-correlation (Net Ecosystem Exchange - NEE) • site ancillary data • Data Access • ORNL DAAC and registered in Mercury • MODIS products to be validated • MOD-17 - 8d PSN/GPP (Gross Primary Productivity) • MOD-17 - ANPP (Annual Net Primary Productivity)

  3. FLUXNET Overview - cont. • Scaling to MODIS pixels • towers sample ~1 km2 area • scaling being addressed by the BigFoot project • Experience in obtaining MODIS data • need to reproject to relate to field studies • Plans to communicate results: Real-Time Validation Exercise • telecons including Instrument Team scientists • post flux, model, and MODIS data on Web page • synthesis papers, workshops planned

  4. FLUXNET Community • Data Component • Dick Olson, ORNL DAAC • Science Component • Dennis Baldocchi, UC-Berkley • Lianhong Gu, UC-Berkley (post-doc) • Eva Falge, U Bayreuth (previous post-doc) • EOS Validation Collaborator • Steve Running, University of Montana • Regional Network Representatives • AmeriFlux, CarboEuroFlux, AsiaFlux, OzNet

  5. FLUXNET Data Users Global Network Non-network sites Regional Networks CARBOEURO- FLUX AmeriFlux AsiaFlux OzNet Oceania Americas Europe Asia - Japan Tower Sites Architecture of Global / Regional Flux Networks

  6. FLUXNET Validation Objectives • Compile flux data (NEE) • gap-filled data for core test sites with flux towers • compile site characteristics • post selected MODIS products • Support Real-Time Validation exercise • host telecons to plan validation • post flux, model, and MODIS data • Quantify controls on flux patterns • provide scientific information to validate or improve underlying model/MODIS algorithms

  7. Recent Results:Quantifying Flux Patterns • Variances across hour-to-year time scales • Annual carbon fluxes by plant functional type • Controls on net CO2 exchange: • light, temperature, humidity deficits and water use, as a function of climate and functional type • length of growing season - temperate broadleaved forests • cloud cover • landscape heterogeneity • stand age on CO2 and water vapor flux densities

  8. FLUXNET Highlights • 3 Regional Networks (AmeriFlux, CARBOEUROPE, AsiaFlux) • 148 towers registered • 62 active towers (submitted data or start year defined) • 306 years of observations for active towers • 103 site-years of data submitted to FLUXNET • 11 years of record at a tower (Harvard) • 12 sites with gap-filled, aggregated data available • 21 site-years of gap-filled, aggregated data available • >3700 ancillary data records (climate, vegetation, LAI, NPP, etc) • >260 parameters in data dictionary • >300 Flux scientists on FLUXNET email server • >3000 Flux related bibliographic citations

  9. Gap-Filled Flux data registered in Mercury

  10. Flux Web Site: http://daac.ornl.gov/FLUXNET/data.html

  11. Net Ecosystem Exchange from eddy correlation, CO2 flux (NEE) Sensible heat from eddy correlation, H Latent heat from eddy correlation, LE Net radiation, R(net) Photosynthetic Active Radiation, PAR Air temperature, T(air) Precipitation, PPT Relative humidity, RH Wind speed & direction Vapor Pressure Deficit, VDP Soil temperature, T(soil) Carbon dioxide concentration, CO2 Soil heat flux, G(soil heat) FLUXNET core variables

  12. 33 sites (EUROFLUX - 14, AmeriFlux - 19) 89 site-years (average of 2.7 years/site)

  13. Synthesis Publications • Overview paper, submitted • Temporal Dynamics and interannual variability of Carbon Dioxide Fluxes • Source-Sink Controls of CO2: Canopy structure and physiological capacity • 1998 Case Study, Spatial Coherence of Fluxes in North America during an El Nino year • Canopy scale responses to drought • Canopy Scale Responses of NEE, GPP and Reco to Environment • Using the FLUXNET spectrum of canopy structure and topography to examine energy balance closure • Examining Energy Exchange Relationships with FLUXNET data

  14. Atqasuk + Blodgett + Bondville + Barrow + Duke Forest - Howland - Happy Valley - Harvard Forest + Little Washita + Metolius - Manaus + Niwot Ridge + BOREAS Old Aspen BOREAS Old Black Spruce + Ponca City - Shilder - Sky Oaks - Old Stand + Sky Oaks - Young Stand + Upad - Walker Branch + Willow Creek Wisconsin Tall Tower Wind River Crane + * Core Sites highlighted in yellow + Ustar correction, - no correction AmeriFlux Sites in Synthesis

  15. Validation of MODIS Products with Flux Data Data from Flux Towers (hourly/daily) Micro-meteorological data MODIS PRODUCTS MOD-17 8-d GPP MOD-17 ANPP VALIDATION Incident PAR Air Temperatures Vapor Pressure Rainfall Wind (seasonal/annual) Land surface properties Land cover Leaf area index Soil carbon Soil nitrogen Biomass (stem) Fluxes : CO2, water and heat Ecosystem models are used to relate Flux tower measurements to MODIS derived products Harvard Forest 1996 Tower vs MOD17 Harvard Forest 1996, Tower vs BGC MOD17 = 0.62*Tower - 0.72 4 8 30 2 R = 0.72 25 6 2 20 4 0 15 2 10 -12 -10 -8 -6 -4 -2 -2 0 2 4 6 0 5 Tmax, (C) NEE, g/m2/day MODIS NPP (g/m2/day) -4 -2 0 100 200 300 400 0 -4 -6 -5 -6 -10 -8 -8 -15 -10 -10 -20 -12 Yearday Tower (daytime), g/m2/day TNEE BGCNEE Tmax TESTING MODIS NPP WITH FLUX TOWER MEASUREMENTS MODELING CARBON FLUXES IN NEAR-REAL TIME Based on Nemani/2/28/00

  16. Real-Time Validation • Micromet data flowing to AmeriFlux (CDIAC) • 15 sites sending data to AmeriFlux • 6 model groups signed up • Univ. of Montana extracting MODIS LAI, fPAR, and NPP products for 11x11 km cutouts • Univ. of Montana and FLUXNET developing model driver data being posted by AmeriFlux • Flux, model, and MODIS results to be posted on AmeriFlux and FLUXNET Web pages • FLUXNET hosting telecons of flux scientists and modelers to review 2000 and plan for 2001

  17. Participating AmeriFlux Sites • Park Falls - deciduous forest • Willow Creek - deciduous forest • U. Mich. Bio. Stn - deciduous forest • Morgan Monroe - deciduous forest • Blodgett - conifer forest • Ponca - cropland • Shidler - grassland • Barrow - tundra • Harvard - deciduous forest • Howland - deciduous forest • Walker Branch - deciduous forest • Duke - conifer forest • Sky Oaks - chaparal * Core Sites high- • Le Selva - tropical forest lighted in yellow

  18. Participating Modeling Groups • Biome-BGC - Running & Nemani, UMT • provided model initialization data for all sites • PNET or OptiCal - Aber et al., UNH • CENTURY - Parton et al., CSU • GTEC - King and Post, ORNL • CASA - Field et al., Stanford • GLO-PEM or CEVAS - Prince & Chao, UMD

  19. Plans for 2001 • Update FLUXNET database • Support Real-Time Validation • periodic telecons • post flux, model, and MODIS data • plan for formal flux-model-MODIS intercomparison • Issues: • minimize lag in acquiring flux data • more robust gap-filling, night-time corrections • conversion of NEE to NPP (estimates of soil respiration flux)

  20. Number of Flux Towers

  21. Key site characteristics (NPP, LAI, fPAR, phenology, climate, hydrology, etc.) compiled from literature, reports, Web sites, and PIs, as well as selected remote imagery; also documented methods, processing, uncertainty, and source.

  22. Core Test Sites and Networks

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