Retrieval of Carbon Dioxide and Methane Concentration from Ground-based Laser Heterodyne Radiometer

NASA Goddard Space and Flight Center (GSFC) has developed a compact, low-cost laser heterodyne radiometer (LHR) for global column measurements of CO₂ and CH₄, the two most important greenhouse gases affecting Earth’s climate. The miniaturized Laser Heterodyne Radiometer (mini-LHR) is a passive, high spectral resolution, ground-based instrument with high absorption measurement sensitivity. This work retrieves atmospheric column-averaged CO₂ and CH₄ concentrations from LHR data by fitting simulated transmittance measurements to LHR’s absorption feature scans from the recent field campaign in Alaska.  Simulated transmittance is produced using the spectroscopy database HITRAN and HITRAN Application Programming Interface (HAPI). Simulated data is then fit to experimental data by matching critical features of each transmittance spectra and adjusting expected CO₂ and CH₄ concentrations.