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

Abstract

<div>We present an analysis of historic pressure and temperature profiles from radiosonde</div><div>launches that will be used in retrieval of mixing fractions for greenhouse gases (GHGs, including</div><div>carbon dioxide, methane, and water vapor) in Laser Heterodyne Radiometry (LHR) data. With</div><div>over 2,700 stations worldwide, the global coverage for weather balloon observations is</div><div>extensive. Radiosonde stations included in the Integrated Global Radiosonde Archive (IGRA),</div><div>are launched simultaneously twice daily at 00:00 and 12:00 UTC. Global stations span all time</div><div>zones in both the Northern and Southern Hemisphere.</div><div>&#160;</div><div>Mesa Photonics and George Washington University are developing a variant of LHR</div><div>known as Precision Heterodyne, Oxygen-Corrected Spectroscopy (PHOCS) that simultaneously</div><div>collects high-resolution, oxygen spectral line shape data. Because oxygen concentrations in the</div><div>troposphere and lower stratosphere are constant, these line shapes are uniquely sensitive to both</div><div>temperature and pressure profiles and constrained fitting of these line shapes enables more</div><div>precise GHG concentration retrievals.</div><div>&#160;</div><div>Our approach is to collect historic data over several years (typically the prior decade) for</div><div>a particular date window surrounding a PHOCS measurement date for stations across the globe,</div><div>and mine this data for observation probability distributions as a function of level altitude, local</div><div>time of day of launch, latitude, etc. These distributions will then be used as Bayesian priors to</div><div>constrain temperature and pressure fits during the oxygen spectral fitting routine. Subsequently,</div><div>these priors will be used to estimate uncertainties in vertically-resolved GHG mixing ratios.</div>