Vertical Profiling of Greenhouse Gas Mixing Ratios Above a Coastal Marsh and In a High Desert Using a Laser Heterodyne Radiometer.

George Washington University and Mesa Photonics are developing a Laser Heterodyne Radiometer (LHR) that simultaneously measures CO₂, CH₄, H₂O, and O₂ mixing ratios throughout the troposphere and lower stratosphere.  One of the prototype instruments is housed in an observatory installed at the Global Change Environmental wetland (GCREW) at the Smithsonian Environmental Research Center (SERC) near Edgewater, Maryland while a nearly identical instrument is located at Mesa Photonics in Santa Fe, NM providing contrast between two very different ecosystems.  The sea level marsh at GCREW is adjacent to a mature secondary upland forest and is also influenced by emissions from the dense population centers within the northeast US megalopolis. The area surrounding the city of Santa Fe, at ~2 km above sea level, is characterized as Juniper scrubland and is sandwiched between Alpine Conifer ecosystems at higher elevations.  The data record from these instruments is anticipated to not only be complementary to other surface concertation and flux measurements but is also expected to be useful in determining transport and land-air surface exchange rates at larger scales. In this presentation, we will review the instrument design and present measurements from both sites spanning these two environments collected throughout the 2023 calendar year. Two spectral areas will be emphasized:           ~1650 nm for quantification of methane and carbon dioxide mixing ratios and ~1278 nm for refined vertical profiling of temperature using fitting of several molecular oxygen transitions.