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www.atmos-meas-tech-discuss.net/4/5837/2011/
doi:10.5194/amtd-4-5837-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Field inter-comparison of two high-accuracy fast-response spectroscopic sensors of carbon dioxide
Earth and Environmental Science Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
Abstract. Tunable diode laser absorption (TDL) and cavity ring-down spectroscopic (CRDS) sensors for atmospheric carbon dioxide were co-deployed during summer and fall of 2010 in the field at Los Alamos National Laboratory. Both sensors were characterized for accuracy and precision for ambient carbon dioxide measurements at ground level and are compared using both laboratory and atmospheric data. After a four point laboratory cross calibration, the mean [12C16O2]TDL = 392.05 ± 8.92 ppm and [12C16O2]CRDS' = 392.22 ± 9.05 ppm between 29 July and 16 August 2010 (mean difference = 0.04 ± 0.04 ppm). The slope of the cross-calibrated linear regression analysis between the two sensors is 1.000. The CRDS sensor is capable of measuring ambient [12C16O2] to a relative precision of 23 ppb Hz−1/2 for a 1-min time constant and this decreases to 6.5 ppb Hz−1/2 for a 58-min time constant. At one and 58-min time constants, the TDL exhibits precisions of 29 ppb Hz−1/2 and 53 ppb Hz−1/2. The CRDS is compact, fast, and stable. The TDL is larger and requires frequent calibrations that limit its time resolution. Field observations show that 1-min averaged data measured by the two instruments agree almost perfectly, for the 19-day period the CRDS/TDL ratio is a Gaussian distribution at x0 = 1.000 ± 3.38 × 10−5. The sensors also exhibit consistent hourly averaged diurnal values underscoring the interplay of biological, anthropogenic, and transport processes regulating CO2 at the site.
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Notice on Discussion StatusCitation: Flowers, B. A., Powers, H. H., Dubey, M. K., and McDowell, N. G.: Field inter-comparison of two high-accuracy fast-response spectroscopic sensors of carbon dioxide, Atmos. Meas. Tech. Discuss., 4, 5837-5855, doi:10.5194/amtd-4-5837-2011, 2011. Bibtex EndNote Reference Manager XML
