# Presentation: 037896

## 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
- 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)

## 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

## 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

## FLUXNET

**Architecture of Global / Regional Flux Networks**

**Tower Sites**

**Global Network**

**FLUXNET**

**Data Users**

**Regional Networks**

**CARBOEURO****-**** FLUX**

- Americas

- Europe

**AmeriFlux**

**AsiaFlux**

**OzNet**

- Asia - Japan

- Oceania

**Non-network sites**

## 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

## Recent Results:Quantifying Flux Patterns

**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

## 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

## Gap-Filled Flux data

**Gap-Filled Flux data**
**registered in Mercury**

## Flux Web Site:

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

## FLUXNET core variables

- 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)**

## 33 sites (EUROFLUX - 14, AmeriFlux - 19)

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

## 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

## AmeriFlux Sites in Synthesis

- 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

## Slide 15

## 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

## 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**

## 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

## 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)

## Number of Flux Towers

## Key site characteristics (NPP, LAI, fPAR, phenology,

- 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.

## Core Test Sites and Networks