Open Path CH4 Analyzer - LI-COR

The LI-7700 Open Path CH 4 Analyzer - Advantages Page 1Innovative SolutionsRemote Field Deployment• Low power (8 W duringnormal operation)• Light weight (5.2 kg)• Low maintenance• Designed for long-term,unattended, continuousoperationEddy Covariance• High precision (5 ppb RMSnoise @ 10 Hz, 2000 ppb CH 4 )• High-speed data output(up to 40 Hz)• Simplified data integration• Analog inputs for sonicanemometer dataOpen Path• In-situ methane densitymeasurement using laserspectroscopy• Enables low power systemoperation• No time delays or attenuationfrom tubing• No pump requiredDesigned for Field Use• Radiation shield minimizescondensation on the uppermirror• Carbon fiber spars minimizethermal expansion of theoptical path• Heaters keep mirrors nearambient temperature toprevent condensationSelf-Cleaning Lower Mirror• Decreases maintenancerequirements• Ensures more robust,continuous data setswasherfluid• Cleaning is initiated atuser-specified time intervalsor a signal strength thresholdGo to www.licor.com/mirror to watch avideo of the LI-7700’s self-cleaning mirror

The LI-7700 Open Path CH 4 Analyzer - Advantages Page 2The LI-7700 Open Path CH 4 AnalyzerThe LI-7700 makes in-situ measurement ofmethane density with the resolution, speed,and stability required for the eddy covariancetechnique.Previously, measuring methane flux was difficultbecause of instrument limitations, including highpower demands, heavy pumps, and the need forinstrument enclosures. The LI-7700 overcomesall of these limitations.The LI-7700 is light weight, has low powerrequirements, and provides high frequencyresponse. The LI-7700 is designed to measuremethane density at frequencies that are necessaryto quantify ecosystem methane flux.Why the LI-7700?• High precision and accuracy• Low power• Long-term, low maintenanceoperation• Easily integrates into flux towers• Simplified data integration• Light weightMeasure CH 4 EverywhereRice paddies, bogs, wetlands, and othermethane-producing ecosystems are unforgivingplaces for scientific instrumentation. TheLI-7700 Open Path CH 4 Analyzer is designed foruse in these remote environments.Methane flux data has been collected with theLI-7700 in a variety of ecosystems under a widerange of environmental conditions - from Arctictundra to mangrove forests.The LI-7700 includes numerous innovations thatreduce the need for site visits, while enablingthe collection of continuous, long-term data setsin remote locations.The open path design eliminates the need forpumps and tubing. Unlike closed path systems,there are no pressure drops, tubing attenuation,or time delays with open path systems.LI-COR recognizes field instruments require adurability that bench-top instruments often lack.The LI-7700 is designed to make high qualitymeasurements in extreme environments.Florida Everglades

The LI-7700 Open Path CH 4 Analyzer - Advantages Page 3Low Power… to go where you need to go.Methane-emitting ecosystems tend to occur inregions that lack easy access to AC power.This complicates measurements of ecosystem methaneflux. The LI-7700 is designed for DC (battery andsolar panel) operation in remote areas and extremeenvironments. This provides you the freedom to takethe instruments wherever you want to measure, withoutbeing constrained by power requirements.

The LI-7700 Open Path CH 4 Analyzer - Advantages Page 4Enhanced Ethernet CapabilitiesThe LI-7700 provides Ethernet data output that allows for quick, easy connectivity to a computer ornetwork. Ethernet connectivity allows you to monitor your instruments remotely, adjust instrumentsettings, and transfer data files over network connections when configured with LI-COR’s CO 2 /H 2 Oanalyzers in GHG packages. Ethernet also facilitates remote data links through cellular modemswhich brings a new level of connection to remote field sites.Simplified Data CollectionThe LI-7700 accepts four analoginput channels for sonic anemometerdata, and outputs a single datastream via the Ethernet connection.With the LI-7550 Analyzer InterfaceUnit data is stored on a removable,industrial-grade USB flash drive(4 GB drive included with LI-7550).Time Methane Density Sonic Anemometer(mmol m -3 ) u (m s -1 ) v (m s -1 ) w (m s -1 ) T (ºC)14:22:15.4 0.08293 -0.87 -1.08 -0.11 22.9714:22:15.5 0.08433 -0.86 -1.08 -0.01 22.9014:22:15.6 0.08436 -0.82 -1.01 0.00 22.8714:22:15.7 0.08386 -0.86 -0.94 0.18 22.8814:22:15.8 0.08326 -0.91 -0.96 0.17 22.9114:22:15.9 0.08458 -0.86 -1.11 0.16 22.8814:22:16.0 0.08289 -0.72 -1.26 -0.01 22.8514:22:16.1 0.08275 -0.70 -1.17 -0.02 22.8214:22:16.2 0.08296 -0.79 -0.98 0.14 22.91Intuitive Windows InterfaceSignal from sonic anemometer is merged with methane data.The Windows ® interface software (included) makes set-up and configuration as simple as possible. Itprovides full control over logging configuration options, auxiliary inputs, and data output. Configurationof mirror heaters and cleaning settings is made easy with the graphical controls. The auto-scaling interfacewindow is designed for viewing on netbook computer displays as well as desktop monitors.Using the LI-7700’s Ethernetcapabilities, a LI-CORscientist monitors real-timedata from instruments setup at the Bluff RoadMunicipal Solid WasteLandfill near Lincoln, NE.

The LI-7700 Open Path CH 4 Analyzer - Technology Page 6Advantages of WMS• Strong signal with low noise• Reduced sensitivity tocontamination of mirrors• Short physical path length• Operation at ambientpressureThe green laser shown at theright is for the purpose of illustrationonly. The LI-7700 uses anear-infrared laser source that isinvisible to the human eye.The LI-7700 was selectedby R&D Magazine as oneof the 100 most innovative,technologically significantproducts of 2010.

The LI-7700 Open Path CH 4 Analyzer - Field Data Page 7Field DataThe figure below shows an example of methane flux data from a 23-day period over the Florida Evergladesat a height of 3.15 m. Under high humidity conditions, the LI-7700 collected data continuouslywith very little user-intervention. Fluxes were obtained with the eddy covariance method using theLI-7700 and a sonic anemometer. The inset shows hourly averages of data collected over a single24-hour period. In this example, reduced wind speeds in the evenings led to lower turbulent exchangeand allowed methane to accumulate in the canopy. Each morning, the build-up was eliminated as windspeeds increased.2.50CH 4concentration, ppm2.252.001.751.506:00 12:00 18:003.050CH 4 Flux, mg m -2 h -1CH 4Concentration, ppm1.50.0-1.5403020Air Temperature, o C-3.01011/19 11/21 11/23 11/25 11/27 11/29 12/1 12/3 12/5 12/7 12/9 12/11Publications which include the LI-7700 :McDermitt, D., G. Burba, L. Xu, T. Anderson, A. Komissarov, J. Schedlbauer, D. Zona , W. Oechel, S.Oberbauer, G. Starr, and S. Hastings, 2010. A New Low-Power, Open Path Instrument for MeasuringMethane Flux by Eddy Covariance. Applied Physics B: Lasers and Optics. Accepted.Burba, G., L. Xu, J. Schedlbauer, D. Zona, T. Anderson, D.K. McDermitt, S. Oberbauer, W. Oechel,A. Komissarov, and B. Riensche, 2010. Eddy Covariance Measurements of Methane Flux at RemoteSites with New Low-Power Lightweight Fast Gas Analyzer. European Geosciences Union GeneralAssembly, Vienna, Austria, 02 – 07 May.Pages 46-52 in the following publication:Burba, G.G., and D.J. Anderson, 2010. A Brief Practical Guide to Eddy Covariance Flux Measurements:Principles and Workflow Examples for Scientific and Industrial Applications. LI-COR Biosciences,Lincoln, USA, Hardbound and Softbound Editions, 212 pp.Go online for more publications: www.licor.com/7700publications

The LI-7700 Open Path CH 4 Analyzer - Field Data Page 8Co-spectraCo-spectral analysis provides a powerful toolto evaluate the capability of the analyzer todetect gas fluctuations over a range of frequencies(Kaimal et al., 1972). It is importantto validate frequency response of any newanalyzer, open-path or closed-path, usingactual field data, and compare it to co-locatedreferences such as a sonic anemometer or anopen-path gas analyzer (e.g., LI-7500).Sometimes it is also useful to compare theactual co-spectral shapes to ideal ones froma model. However, the modeled shapesmay not always account for specificities andimperfections of study site topography andairflows, while sonic anemometer temperatureflux co-spectra generally do account forthese and are a practical reference of nearlyperfectfrequency response.The figures to the right show ensembleaverages of normalized daytime co-spectraplotted versus non-dimensional frequency forcontrasting ecosystems and measurementheights at a 10 Hz sampling rate.Normalized co-spectra, nC wx /W’X’In all cases, methane co-spectra behavedsimilarly to the co-spectra of CO 2 , H 2 O, andair temperature. This demonstrates that theLI-7700 configuration is suitable for measuringfluctuations in CH 4 concentration acrossthe whole spectrum of frequencies thatcontributed to turbulent transport at thesemeasurement heights.All the co-spectra followed the Kaimal model(Kaimal et al., 1972).Kaimal J., J. Wyngaard, U. Izui, and O. Cote.1972. Spectral characteristics of surface-layerturbulence. Quart. J. Roy. Meteor. Soc, 98:563-589.Non-dimensional frequency, f=nz/Uw’T’ w’CO 2 w’CH 4 TDLSKaimal slopeExpected instrument slope at highfrequencyField data illustrate that theLI-7700 has the frequencyresponse required to sample therange of eddy frequencies thatcontribute to methane flux.

The LI-7700 Open Path CH 4 Analyzer - Eddy Covariance System Page 93-Gas Eddy Covariance SystemFor a multi-gas system, the LI-7550 Analyzer Interface Unit can be used to integrate an LI-7700, aCO 2 /H 2 O analyzer such as the LI-7500A Open Path CO 2 /H 2 O Analyzer or LI-7200 Enclosed CO 2 /H 2 OAnalyzer and a sonic anemometer. When using the LI-7700 to calculate methane flux, it is criticalthat a high speed H 2 O analyzer be used for water vapor correction.The figure below shows methane, carbon dioxide, and latent heat fluxes measured with the eddycovariance technique over the Florida Everglades. These data are a subset of a 6-week data setcollected during the winter of 2008-09, at 3.15 m above the canopy, using an LI-7500 Open PathCO 2 /H 2 O Analyzer and an LI-7700 Open Path CH 4 Analyzer. They show a net negative flux of CO 2 ,but positive CH 4 and LE fluxes for the measurement period, indicating that this ecosystem was a sinkof carbon dioxide and a source of methane and water vapor.CH 4Flux (mg/m 2 /h)CO 2Flux (g/m 2 /h)5.0 0.31202.5 0.150-2.5 -0.15-5.0 -0.3-120338 339 340 341 342 343 344 345 346Day of Year600-60LE (W/m 2 )Both the LI-7700 Open Path CH 4 Analyzer and the LI-7550 Analyzer Interface Unit provide fourgeneral ±5 V inputs for analog data from any fast sonic anemometer. The LI-7700 also provides threetype E thermocouple inputs for recording additional temperature data if desired. LI-COR sonic anemometercables (optional) allow you to easily integrate analog data from Gill WindMaster/Pro orCampbell ® Scientific CSAT-3 sonic anemometers with the LI-7700 data stream. Weatherproof cableterminals provide simple and reliable electrical connections.Greenhouse Gas Pacakges from LI-COR:Greenhouse gas analyzer systems from LI-COR Biosciences facilitate the collection of eddy covariancedata sets by logging CH 4 , CO 2 , and H 2 O density data, along with wind speed, direction, andtemperature data (u, v, w, and T s ) to a removable USB data storage device. Data can also be transferredvia Ethernet to an external data storage device or computer network.LI-COR offers two Greenhouse Gas Packages which include the LI-7700 CH 4 Analyzer with eitherthe LI-7500A Open Path CO 2 /H 2 O Analyzer or LI-7200 Enclosed CO 2 /H 2 O Analyzer. Sonic anemometerscan also be purchased from LI-COR.

For use with:• LI-72 0 CO2/H2O Analyzer• LI-75 0A CO2/H2O• LI- 7 0 CH4 AnalyzerThe LI-7700 Open Path CH 4 Analyzer - Eddy Covariance System Page 10Typical Eddy Covariance ConfigurationCH 4 AnalyzerIntegrates easily into new or existing towers.CO 2 /H 2 O AnalyzerLI-COR’s LI-7500A Open Path Analyzer (shown in thediagram) and LI-7200 Enclosed Analyzer make precise,accurate, and fast measurements. A CO 2 /H 2 O analyzeris a core component of a flux tower.Sonic AnemometerMeasures wind speed and direction. LI-COR’s flexiblesystem allows for the integration of any sonic anemometerthat has analog outputs.The LI-7550 Analyzer Interface UnitUsed for data acquisition from the LI-7700, as well as dataacquisition and control of the sonic anemometer and CO 2 /H 2 Oanalyzer. Data can be output through Ethernet, or stored internallyon a removable industrial-grade USB drive.7700-101 Washer Assembly (included)Supplies washer fluid for automated washingof lower mirror surface.Solar PanelsWith low power requirements (nominally 8W for LI-7700, 20Wfor LI-7700 and LI-7500A), LI-COR’s system can be easilyoperated on solar panels and batteries.