Statistical Characterization of Temperature and Pressure Vertical Profiles for the Analysis of Laser Heterodyne Radiometry Data.

The statistical analysis of historic pressure and temperature profiles from radiosonde launches for use in the fitting of molecular oxygen line shapes is presented. As the O2 mixing ratio is nearly constant throughout the lower atmosphere, only variations in pressure and temperature profiles will affect the fit of observed O2 features in Laser Heterodyne Radiometry (LHR) spectra. Radiosonde temperature and pressure data are extracted from the Integrated Global Radiosonde Archive (IGRA) for a given station, date, and launch time. Data may be extracted for a single launch, for the same date over several years, and/or within a window centered on a target date. The temperature and pressure profiles are further characterized by the statistical variation in coefficients of polynomial fits in altitude. The properties of the probability distributions for each coefficient are used to constrain fits of O2 line shapes through Nelder-Mead optimization. The refined temperature and pressure profiles are then used in the retrieval of vertically resolved mixing ratios for greenhouse gases (GHGs) measured in the same instrument. In continuous collections, each vertical profile determination may be treated as a Bayesian prior to inform subsequent measurements and provide an estimate of uncertainties.

Precision heterodyne oxygen-corrected spectrometry: vertical profiling of water and carbon dioxide in the troposphere and lower stratosphere.

We describe the development of a near-infrared laser heterodyne radiometer: the precision heterodyne oxygen-corrected spectrometer (PHOCS). The prototype instrument is equipped with two heterodyne receivers for oxygen and water (measured near 1278 nanometers) and carbon dioxide (near 1572 nanometers) concentration profiles, respectively. The latter may be substituted by a heterodyne receiver module equipped with a laser to monitor atmospheric methane near 1651 nanometers. Oxygen measurements are intended to provide dry gas corrections and-more importantly-determine accurate temperature and pressure profiles that, in turn, improve the precision of the ${{\rm CO}_2}$CO2 and ${{\rm H}_2}{\rm O}$H2O column retrievals. Vertical profiling is made feasible by interrogating the very low-noise absorption lines shapes collected at $ \approx {0.0067}\;{{\rm cm}^{ - 1}}$≈0.0067cm-1 resolution. PHOCS complements the results from the Orbiting Carbon Observatory (OCO-2), Active Sensing of ${{\rm CO}_2}$CO2 Emissions over Nights, Days, and Seasons (ASCENDS), and ground-based Fourier transform spectrometers. In this paper, we describe the development of the instrument by Mesa Photonics and present the results of initial tests in the vicinity of Washington, DC.