HR: 0830h
AN: A51D-0717    [PDF]
TI: Field and Laboratory Measurements of Carbon Dioxide Mixing Ratios in Air Using the LI-COR LI-7000 CO$_{2}$/H$_{2}$O Analyzer
AU: Murphy, P C
EM: pcmuphy@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305-3337 United States
AU: Murphy, P C
EM: pcmuphy@al.noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO 80309-0216 United States
AU: * Lerner, B M
EM: blerner@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305-3337 United States
AU: * Lerner, B M
EM: blerner@al.noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO 80309-0216 United States
AU: Williams, E J
EM: eric@al.noaa.gov
AF: Aeronomy Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO 80305-3337 United States
AU: Williams, E J
EM: eric@al.noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO 80309-0216 United States
AB: Air measurements of CO$_{2}$ were made with a LI-COR LI-7000 CO$_{2}$/H$_{2}$O analyzer on the NOAA ship Ronald H. Brown during the New England Air Quality Study (NEAQS 2002) field campaign. This instrument is an improved version of the older model LI-6262 CO$_{2}$/H$_{2}$O analyzer, which uses a non-dispersive IR radiation absorption technique. During NEAQS, we operated the LI-7000 without temperature regulation, using a simple 2-point calibration scheme. An intercomparison between our measurements of atmospheric CO$_{2}$ mixing ratios and those measured by a more sophisticated method, using temperature-regulation and a multipoint calibration with a LI-6252 CO$_{2}$ analyzer (operated by AOML) shows generally good results ([CO$_{2}$]AL = [CO$_{2}$]AOML $\times$ 1.015 (0.010) - 5.7 (3.8) ppmv; R$^{2}$ = 0.9889) in highly variable air masses. During subsequent laboratory studies, we evaluated the instrument for the manufacturer's claims of improvement in signal noise, sample gas temperature equilibration and zero drift with temperature. Further work examined the instrument's susceptibility to rapid temperature changes, which has been previously demonstrated to introduce error of several ppmv $\deg$C$^{-1}$ in the LI-6252. A change in the LI-7000 optical bench temperature of 12 $\deg$C in 1 hour caused a sampling error of $\sim$3 ppmv CO$_{2}$. Therefore, our lab investigations indicate that the LI-7000 would benefit from a temperature-controlled enclosure, as is used by the AOML group.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0365 Troposphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting