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

We present an analysis of historic pressure and temperature profiles from radiosonde

launches that will be used in retrieval of mixing fractions for greenhouse gases (GHGs, including

carbon dioxide, methane, and water vapor) in Laser Heterodyne Radiometry (LHR) data. With

over 2,700 stations worldwide, the global coverage for weather balloon observations is

extensive. Radiosonde stations included in the Integrated Global Radiosonde Archive (IGRA),

are launched simultaneously twice daily at 00:00 and 12:00 UTC. Global stations span all time

zones in both the Northern and Southern Hemisphere.

 

Mesa Photonics and George Washington University are developing a variant of LHR

known as Precision Heterodyne, Oxygen-Corrected Spectroscopy (PHOCS) that simultaneously

collects high-resolution, oxygen spectral line shape data. Because oxygen concentrations in the

troposphere and lower stratosphere are constant, these line shapes are uniquely sensitive to both

temperature and pressure profiles and constrained fitting of these line shapes enables more

precise GHG concentration retrievals.

 

Our approach is to collect historic data over several years (typically the prior decade) for

a particular date window surrounding a PHOCS measurement date for stations across the globe,

and mine this data for observation probability distributions as a function of level altitude, local

time of day of launch, latitude, etc. These distributions will then be used as Bayesian priors to

constrain temperature and pressure fits during the oxygen spectral fitting routine. Subsequently,

these priors will be used to estimate uncertainties in vertically-resolved GHG mixing ratios.