Séminaire Pr.Houston Miller - Université de Washington

Labex CAPPA

Séminaire Pr.Houston Miller - Université de Washington

Vertical Profiling of Greenhouse Gas Mixing Ratios Above  a Coastal Marsh Using a Laser Heterodyne Radiometer

Abstract :

George Washington University and Mesa Photonics have developed 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.  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 data record from this instrument is anticipated to not only be complementary to other co-located surface concentration 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 collected throughout the 2023 calendar year. Two spectral regions 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. A challenge in this deployment has been in processing and interpreting the vast amount of raw data produced, consisting of ~ 1 GB per 8 hours of data collection in a compressed format, or ~16 GB as human-readable text. After an introduction to the technology, the presentation will focus on our retrieval algorithm as well as a sensitivity analysis to establish measurement uncertainty.

Contact : Xavier Mercier xavier.mercier[chez]univ-lille[point].fr