Evaluation of the airborne quantum cascade laser spectrometer (QCLS) measurements of the carbon and greenhouse gas suite – CO<sub>2</sub>, CH<sub>4</sub>, N<sub>2</sub>O, and CO – during the CalNex and HIPPO campaigns

Abstract

Abstract. We present an evaluation of aircraft observations of the carbon and greenhouse gases CO 2 , CH 4 , N 2 O, 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 CO 2 , CH 4 , N 2 O, 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 CO 2 and CH 4 (CalNex), two broadband non-dispersive infrared (NDIR) spectrometers measuring CO 2 (HIPPO), two onboard gas chromatographs measuring a variety of chemical species including CH 4 , N 2 O, 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 CO 2 , CH 4 , N 2 O, 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.

Impacts of updated spectroscopy on thermal infrared retrievals of methane evaluated with HIPPO data

“…HIPPO CH 4 data are reported on the NOAA calibration scale and have been used in several other studies to evaluate satellite retrievals of CH 4 (e.g., Wecht et al, 2012;Crevoisier et al, 2013;Massart et al, 2014). Comparisons with flask data from the NOAA Whole Air Sampler (NWAS) showed a mean positive bias of 0.85 ppb for the QCLS measurements against the NOAA flask data during the HIPPO campaigns, which is consistent with the estimated QCLS accuracy of 1.0 ppb (Santoni et al, 2014). …”

The MOPITT Version 6 product: algorithm enhancements and validation

“…Observations were made during January 2009 (Phase 1), October/November 2009 (Phase 2), March/April 2010 (Phase 3), June/July 2011 (Phase 4), and August/September 2011 (Phase 5). In situ measurements of atmospheric composition were performed using the QCLS (quantum-cascade laser spectrometer) instrument (Santoni et al, 2014) from approximately 67 • S to 80 • N mostly over the Pacific Ocean, and over a wide altitude range (from the surface up to pressures of 150-300 hPa). The extensive coverage of the HIPPO flights makes this data set useful for analyzing the geographical dependence of retrieval biases .…”

Bias corrections of GOSAT SWIR XCO<sub>2</sub> and XCH<sub>4</sub> with TCCON data and their evaluation using aircraft measurement data

“…In order to test for remaining biases in the GOSAT data after applying the empirical correction developed using TCCON data, we use aircraft profile data provided by the Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) project (Machida et al, 2008), the NOAA Earth System Research Laboratory/Global Monitoring Division (ESRL/GMD; Xiong et al, 2008;Sweeney et al, 2015), the US Department of Energy (DOE; Biraud et al, 2013;Schmid et al, 2014), the National Institute for Environmental Studies (NIES; Machida et al, 2001), the Japan Meteorological Agency (JMA; Tsuboi et al, 2013), the HI-APER Pole-to-Pole Observations (HIPPO) project (Wofsy et al, 2011Kort et al, 2012;Santoni et al, 2014), and an aircraft measurement campaign by NIES and the Japan Aerospace Exploration Agency (JAXA) (Tanaka et al, 2012). To calculate aircraft-based XCO 2 and XCH 4 (as described in the next paragraph), we also used tower data from the Meteorological Research Institute (MRI) in Tsukuba (Inoue andMatsueda, 1996, 2001) and the NOAA ESRL/GMD tall tower network in Park Falls, WI and West Branch, IA .…”