Abstract
Abstract. We present an evaluation of aircraft observations of the carbon and greenhouse gases CO2, CH4, N2O, and CO using a direct-absorption pulsed quantum cascade laser spectrometer (QCLS) operated during the HIPPO and CalNex airborne experiments. The QCLS made continuous 1 Hz measurements with 1σ Allan precisions of 20, 0.5, 0.09, and 0.15 ppb for CO2, CH4, N2O, and CO, respectively, over > 500 flight hours on 79 research flights. The QCLS measurements are compared to two vacuum ultraviolet (VUV) CO instruments (CalNex and HIPPO), a cavity ring-down spectrometer (CRDS) measuring CO2 and CH4 (CalNex), two broadband non-dispersive infrared (NDIR) spectrometers measuring CO2 (HIPPO), two onboard gas chromatographs measuring a variety of chemical species including CH4, N2O, and CO (HIPPO), and various flask-based measurements of all four species. QCLS measurements are tied to NOAA and WMO standards using an in-flight calibration system, and mean differences when compared to NOAA CCG flask data over the 59 HIPPO research flights were 100, 1, 1, and 2 ppb for CO2, CH4, N2O, and CO, respectively. The details of the end-to-end calibration procedures and the data quality assurance and quality control (QA/QC) are presented. Specifically, we discuss our practices for the traceability of standards given uncertainties in calibration cylinders, isotopic and surface effects for the long-lived greenhouse gas tracers, interpolation techniques for in-flight calibrations, and the effects of instrument linearity on retrieved mole fractions.
Highlights
Growing interest in understanding the drivers of climate change has sparked innovation in instrumentation to measure long-lived greenhouse gases and associated chemical tracers (Chen et al, 2010; Fried et al, 2009; Nelson et al, 2004; O’Shea et al, 2013; Xiang et al, 2013a; Zahniser et al, 2009; Zare et al, 2009)
We present an overview of the quantum cascade laser spectrometer (QCLS) sensor used on two airborne campaigns – the HIAPER Pole-to-Pole Observations (HIPPO; Wofsy et al, 2011) campaign on the NCAR HIAPER-GV and the California Research at the Nexus of Air Quality and Climate Change experiment (CalNex; Ryerson et al, 2012) on the National Oceanic and Atmospheric Administration (NOAA) P-3 – and present measurement comparisons with other onboard sensors and flask samplers
We evaluate the traceability of calibration standards from the World Meteorological Organization (WMO) and National Oceanic and Atmospheric Administration (NOAA) calibrated values to the in-flight standards as well as long-term sensor stability
Summary
Growing interest in understanding the drivers of climate change has sparked innovation in instrumentation to measure long-lived greenhouse gases and associated chemical tracers (Chen et al, 2010; Fried et al, 2009; Nelson et al, 2004; O’Shea et al, 2013; Xiang et al, 2013a; Zahniser et al, 2009; Zare et al, 2009). Many sensors rely on the accuracy of spectroscopic parameters (e.g., line strengths and their pressure and temperature dependencies) to derive in situ “spectroscopically calibrated” mixing ratios from raw spectra (Rothman et al, 2009; Zahniser et al, 1995). The use of these raw data is often appropriate, if (1) a sensor is linear with respect to the range of observed concentrations, and (2) the quantity of interest is the relative enhancement of one chemical tracer versus another or versus background values measured on the same sensor. In the context of traceability and sensor accuracy, we discuss sample conditioning, surface equilibration effects, and isotopic effects on calibration standards
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
