Twenty-Five-Fold Reduction in Measurement Uncertainty for a Molecular Line Intensity

Abstract

To accurately attribute sources and sinks of molecules like CO2, remote sensing missions require line intensities (S) with relative uncertainties ur (S) < 0.1 %. However, discrepancies in S of ≈1 % are common when comparing different experiments, thus limiting their potential impact. Here we report a cavity ring-down spectroscopy multi-instrument comparison which revealed that the hardware used to digitize analog ring-down signals caused variability in spectral integrals which yield S. Our refined approach improved measurement accuracy twenty-five-fold, resulting in ur(S) = 0.06 %.

High‐Accuracy Near‐Infrared Carbon Dioxide Intensity Measurements to Support Remote Sensing

“…These results illustrate agreement between our measurements and the ab initio calculations of Zak et al () at the 0.06% level for the (30013) ← (00001) and (30014) ← (00001) band intensities, but a systematic discrepancy of about −1.1% for the (30012) ← (00001) band. We also note that our fitted intensity value for the R16e (30012) ← (00001) transition reported here is within 0.10% of the value reported in Fleisher et al ().…”

“…The sample pressures were recorded with high-precision gauges that were calibrated against a NIST transfer pressure standard, yielding relative uncertainties near 0.01%. We also corrected for an important measurement bias caused by nonlinearity in the digitizer boards used to acquire the ring-down signals (Fleisher et al, 2019). The relative uncertainty of the measured decay rates after this correction was estimated to be 0.04%.…”

Absolute 13C/12C isotope amount ratio for Vienna PeeDee Belemnite from infrared absorption spectroscopy

“…Digitizer linearity. Linearity of the analog-to-digital acquisition cards was tested using synthetic exponential decay signals (SEDS) and a metrology-grade reference digitizer as a transfer standard 34 . The SEDS of 1 ms in length were constructed using an arbitrary waveform generator with 14-bit vertical resolution and a sampling rate of 128 MS/s.…”

“…C,18 O,17 O,15 N, 2 H, and34 S. For stable carbon isotope ratios, our own efforts to ascertain more accurate values for13 C 16 O 2 transition intensities in the 2 μm wavelength region using gravimetrically prepared, potentially isotopically enriched gas samples with traceability to the kilogram are just beginning. Accurate measurements of analogous 12 C 16 O 2 transitions could also reduce uncertainty in the 13 C 16 O 2 ab initio predictions (Supplementary Information, Section S2).…”

Field Evaluation of Column CO2 Retrievals From Intensity‐Modulated Continuous‐Wave Differential Absorption Lidar Measurements During the ACT‐America Campaign

“…At the moment, it is still arguable if this change (in this particular band) is justified, as alternative ab initio calculations (Huang et al, 2014(Huang et al, , 2017 favor Toth et al (2006) data while independent experiments cannot provide conclusive justification (see for instance Devi et al, 1998;Jacquemart et al, 2012) at the required level of accuracy. New experiments and atmospheric validations are now underway to resolve this issue (c.f., Fleisher et al, 2019), and we may have to reevaluate our model to accommodate data from the official HITRAN2016 release.…”