Bridging the Gap in Scales between Flux Towers, Ecosystem Models and Remote Sensing R.J. Olson 1, R.B. Cook 1, L.M. Olsen 1, T. A. Boden 1, J.T. Morisette 2, and S.W. Running 3 1 Oak Ridge National Laboratory, Environmental Sciences Division, Oak Ridge, TN United States* 2 Goddard Space Flight Center, NASA, Code 923, Greenbelt, MD United States 3 University of Montana, School of Forestry, Missoula, MT United States Abstract Combining ground-based studies, ecosystem models, and remote sensing data provides a broad basis for understanding the dynamics of ecosystem-atmosphere CO 2 exchange. Data from a global network of flux tower sites (FLUXNET) are being compared to ecosystem model outputs and to remote sensing products, such as the photosynthesis product derived from the MODIS sensor on the Terra satellite. Comparison of information from multiple types of local and regional studies is needed prior to extrapolating site studies to larger-scale products derived from remote sensing or global-scale modeling. This poster describes data being compiled by the ORNL DAAC to conduct the local and regional scale validation of remote sensing products. The FLUXNET database contains carbon, water vapor, sensible heat, momentum, and radiation flux measurements with associated ancillary and value-added data products for a wide range of ecosystems on five continents. The MODIS land products are 1-km resolution data in the immediate vicinity of the flux tower. Modeling groups are using the data to run terrestrial biosphere models for 17 flux tower sites to compare model outputs, flux measurements, field measurements, and MODIS products. AmeriFlux, the network of flux towers in the Americas, provides model initialization and driver data for this exercise. Abstract Combining ground-based studies, ecosystem models, and remote sensing data provides a broad basis for understanding the dynamics of ecosystem-atmosphere CO 2 exchange. Data from a global network of flux tower sites (FLUXNET) are being compared to ecosystem model outputs and to remote sensing products, such as the photosynthesis product derived from the MODIS sensor on the Terra satellite. Comparison of information from multiple types of local and regional studies is needed prior to extrapolating site studies to larger-scale products derived from remote sensing or global-scale modeling. This poster describes data being compiled by the ORNL DAAC to conduct the local and regional scale validation of remote sensing products. The FLUXNET database contains carbon, water vapor, sensible heat, momentum, and radiation flux measurements with associated ancillary and value-added data products for a wide range of ecosystems on five continents. The MODIS land products are 1-km resolution data in the immediate vicinity of the flux tower. Modeling groups are using the data to run terrestrial biosphere models for 17 flux tower sites to compare model outputs, flux measurements, field measurements, and MODIS products. AmeriFlux, the network of flux towers in the Americas, provides model initialization and driver data for this exercise. Data for a typical site - Walker Branch Watershed (WBW), Oak Ridge, TN Photo of tower located at Walker Branch Watershed. Vegetation consists of mixed species of broad-leaved deciduous forest. IKONOS Image of Walker Branch Watershed. MOD09A1 - Surface Reflectance ISIN or UTM? To reproject or not to reproject…? Flux Tower location ISIN MOD12Q1- Quarterly Land Cover Flux Tower location MOD12Q1- Quarterly Land Cover Flux Tower MODIS B52A-02 Soil CO 2 N2N2 Fire Biological N Fixation P required Decomposition Rubisco Stomata Leaf Wood Denitrification Leaching N 2 O, N 2 Soil water Allocatio n Model of C,N,P and H 2 O in terrestrial systems Source: Bob Scholes, July 2001, Amsterdam The Array of Scales Represented in the Various Sources of Data Source Scale Flux Towers In situ Measure- ments Remote Sensing (ETM, IKONOS) MODIS Products Models ParameterNEE, respirationLAI, NPP, respiration Land cover, NDVI, etc. fPAR, Vi, LAI, PSN, NPP NPP, NEP, LAI SpatialVarying footprint (~1 km 2 ) Points (<1 m 2 ) 30 m and finer1x1 kmPoint Temporal0.5 hrPeriodic, Annual Periodic8-day composite Daily FPAR - FPAR high low water April 7 May 25 July 14 Sept 30 Fraction of Photosynthetically Active Radiation (MOD15A2) l LAI April 7 May 25 July 14 Sept 30 high low water Leaf Area Index (MOD15A2) Index (MOD13A2) lowhigh water EVI April 7 May 25 July 14 Sept 30 Enhanced Vegetation Index (MOD13A2) low high PSN April 7 May 25 July 14 Sept 30 Daily Photosynthesis (MOD17A2) MODIS Products 8-day composites Top panels show spatial pattern of 1x1-km pixels in 7x7-km subset centered on flux tower. EVI is a 16-day composite product. Lower panels show temporal patterns of pixels with good QA flags, red line is pixel containing tower, dots are pixels near tower ASCII Subsets available at: //public.ornl.gov/fluxnet/modis.cfm MODIS Products 8-day composites Top panels show spatial pattern of 1x1-km pixels in 7x7-km subset centered on flux tower. EVI is a 16-day composite product. Lower panels show temporal patterns of pixels with good QA flags, red line is pixel containing tower, dots are pixels near tower ASCII Subsets available at: //public.ornl.gov/fluxnet/modis.cfm Remote Sensing Ecosystem Models Ecosystem Models EOS Core Validation Sites Participating Modelers Lotec: ORNL – King Biome BGC: UMT – Running PnET: UNH - Aber Participating Modelers Lotec: ORNL – King Biome BGC: UMT – Running PnET: UNH - Aber Many Scales: Need a Scientific Strategy and Information Management Strategy to Bridge Scales Many Scales: Need a Scientific Strategy and Information Management Strategy to Bridge Scales Contact Information: R. J. Olson *Managed by the University of Tennessee-Battelle LLC under contract DE-AC05-00OR22725 with the U.S. Department of Energy Contact Information: R. J. Olson *Managed by the University of Tennessee-Battelle LLC under contract DE-AC05-00OR22725 with the U.S. Department of Energy Making MODIS Products Available: 7x7-km ASCII Subsets Centered on Towers UTM Difficult to collocate field measurements within remote sensing pixels Difficult to collocate field measurements within remote sensing pixels In situ Measurements In situ Measurements Measuring soil Respiration on Walker Branch Watershed

Summary Strategies for supporting validation have been designed and reviewed - tested and refinements are ongoing Distribution systems are in place and working Validation data are available and more data are being added Plans are in place to hold workshops and communicate validation results via special journal issues Summary Strategies for supporting validation have been designed and reviewed - tested and refinements are ongoing Distribution systems are in place and working Validation data are available and more data are being added Plans are in place to hold workshops and communicate validation results via special journal issues Strategies for Bridging Scales to Compare Diverse Observations Data Resources for Many Applications Available for EOS Core Sites Ongoing Concerns Testing and refining of the comparison strategies are needed Spatial differences - scaling of points to cells, comparing one pixel vs. subsets Temporal differences – satellite 8-day vs. field observation on a specific day Data inconsistencies - methods, variables, formats Sites - 26 core and ~170 towers site; need for a wider variety of ecosystem types Ongoing Concerns Testing and refining of the comparison strategies are needed Spatial differences - scaling of points to cells, comparing one pixel vs. subsets Temporal differences – satellite 8-day vs. field observation on a specific day Data inconsistencies - methods, variables, formats Sites - 26 core and ~170 towers site; need for a wider variety of ecosystem types Data Collection and Flux-Model-MODIS Comparisons are Ongoing MODIS PSN for 2001 (red) and NEE for MODIS PSN for 2001 and Biome BGC Model NEP Outputs for 2000 and 2001 Gap-filled Flux Tower NEE for Years differ, MODIS 8-day composite (best day in period) multiplied by 8 ½ hr NEE data gap- filled and summed to 8-day periods Biome BGC Model NEP for 2000 and 2001 and NEE for Daily model outputs summed to 8-day periods Daily model outputs summed to 8-day periods Formal Comparisons Ecosystem Model-Data Intercomparison (EMDI 3) - 12 Modeling Groups - NPP, NEE flux, MODIS products - Kathy Hibbard, - Santa Barbara, CA; April 21-24, 2002 MODIS Vegetation Workshop - Products: fPAR, LAI, VI, PSN - Steve Running, - Missoula, MT, July 16-18, Formal Comparisons Ecosystem Model-Data Intercomparison (EMDI 3) - 12 Modeling Groups - NPP, NEE flux, MODIS products - Kathy Hibbard, - Santa Barbara, CA; April 21-24, 2002 MODIS Vegetation Workshop - Products: fPAR, LAI, VI, PSN - Steve Running, - Missoula, MT, July 16-18, B52A-02 URLs for Data URLs for Data Data TypeData CenterURL Flux dataFLUXNETwww.daac.ornl.gov/FLUXNET/fluxnet.html Model Driver and Initial Parameters AmeriFluxpublic.ornl.gov/ameriflux/Analysis/Model_Evaluation/index.html EOS Core SitesNASA GSFCmodarch.gsfc.nasa.gov/MODIS/LAND/VAL/ MODIS SubsetsORNL DAACpublic.ornl.gov/fluxnet/modis.cfm MODIS ImagesEDC DAACedcdaac.usgs.gov/modis/dataprod.html In Situ dataMercury Systemmercury.ornl.gov/ornldaac/ Comparison Workshops CDIAC/AmeriFlux Model initialization parameters Weekly micromet data Initial 0. 5 hr flux data DAAC/FLUXNET MODIS products – 7x7 cutouts FLUXNET gap-filled data Links to field data via Mercury MODIS 25 sites 8 products Modeling Groups Estimating NPP and NEP for flux towers Individual Site Data Additional validation data Information Management Strategy: Collocate data at central site or with Internet links First Steps to Bridge the Gap in Scales, Illustrated with Walker Branch Watershed Data Validation “Assessing by independent means the uncertainties of data products” Model Outputs (ensemble including Biome BGC) versus Measured NPP MODIS LAI (2001) – red line - 8-day composites with high quality QA flags - average of 1x1 km pixels near flux tower Field LAI measurements (1996 – 1999) - relative LAI with max LAI=1.0 - measured at a point near tower - Source: Paul Hanson, ORNL Comparisons - MODIS LAI shows similar greening pattern in spring as field data; however, fall pattern shows earlier leaf-off - it is not clear why the MODIS LAI shows significant drop around day 151 Comparing MODIS LAI product to LAI field measurements WBW is a deciduous forest with annual leaf-on and leaf-off phenology Models tended to be higher than data at low NPP sites, lower at high NPP sites MODIS PSN is mean of 3x3-km subset, BGC NEP is for tower site MODIS PSN is mean of 3x3-km subset, BGC NEP is for tower site 1.26 Core Sites in 6 biomes, sites with active research programs 2.Flux towers using eddy covariance methods to sample large footprint 3.Gap-filling of flux data to create complete temporal record 4.BigFoot project to develop spatial scaling methods 5.Fine-scale remote sensing to scale-up point measurements 6.Models to estimate parameters that are difficult to measure and to bridge scales Scientific Strategy: Collocate data in time and space Scientific Strategy: Collocate data in time and space