Combined Lidar Measurements of Methane, Aerosols, and Planetary Boundary Layer Heights with the NASA High Altitude Lidar Observatory

NASA Langley Research Center has developed the High Altitude Lidar Observatory (HALO) system to address the observational needs of NASA’s weather, climate, carbon cycle, and atmospheric composition focus areas. HALO is a modular and multi-function airborne lidar developed to measure atmospheric H₂O and CH₄ mixing ratios and aerosol/cloud/ocean optical properties using the Differential Absorption Lidar (DIAL) and High Spectral Resolution Lidar (HSRL) techniques, respectively. During the summer of 2018 HALO deployed on the Langley B200 aircraft in the Long Island Sound Tropospheric Ozone Study air quality field campaign. HALO also participated in the final ACT-America airborne campaign during the summer of 2019. The CH₄configuration employed for both campaigns exploited the DIAL technique at 1645 nm for column and multi-layer measurements of CH₄mole fractions, and the HSRL technique at 532 nm to make independent, unambiguous retrievals of aerosol extinction and backscatter profiles. The addition of the HSRL channels provides context to the airborne CH₄ DIAL measurements, especially the layered structure of the atmosphere including vertical mixing through planetary boundary layer height retrievals, and provides the critical capability to validate aerosol and cloud induced biases from passive space-borne measurements of column CH₄. In this presentation we will provide a brief overview of the HALO instrument capabilities, and present preliminary HALO CH₄ measurements spanning a wide range of sources over varying atmospheric and surface conditions. We will also present on the new HALO capability of apportioning the average PBL methane mixing ratio from the total column in clear atmospheric conditions where the traditional cloud slicing method is not possible using fair weather PBL cloud tops. Column and PBL methane mixing ratios as well as PBL heights retrieved from HALO will be compared against coincident TROPOMI overpasses and in situ validation measurements. We will also compare observed and simulated XCH4 to solve for sources. Flights over the gas, oil and coal production regions of the southern and eastern United States, and downwind of coastal wetlands, will be used to quantify methane emissions from these sources.