Design of a Mobile Tropospheric Ozone Lidar and Ozone Profiling in New York During Summer 2023

A mobile tropospheric Ozone (O₃) Differential Absorption Lidar (DIAL) system was recently developed at the City College of New York (CCNY) as part of the Tropospheric Ozone Lidar Network (TOLNET). The lidar system is housed in a vibration-absorbing mechanical frame that is installed in a 20-ft long trailer, allowing it to be deployed at sites of interest for measuring O₃ profiles during field campaigns. The lidar transmitter consists of a quadrupled Nd:YAG laser that generates 50 mJ pulses of 266 nm light at a repetition rate of 20 Hz. The laser pumps a CO₂ Raman cell pressurized to 160 psi, producing “online” and “offline” wavelengths of 287.2 nm, and 299.1 nm through Stimulated Raman Scattering (SRS). The receiver consists of long-range and a short-range channels to improve the overall dynamic range of the lidar system. The long-range channels utilize a 20-inch diameter Cassegrain telescope while the short-range channels utilize a 2-inch refractive telescope coupled with an optical fiber. The mobile O₃ lidar was validated against the CCNY laboratory O₃ lidar in July 2023. The results show that the mobile O₃ lidar can retrieve O₃ from around 500 m to 4.5 km and that the O₃ retrievals are generally consistent between the two O₃ lidars. As part of the summer 2023 NOAA CUPiDS and NASA STAQS campaigns, the mobile O₃ lidar was deployed to Columbia University Lamont-Doherty Earth Observatory (LDEO) in Palisades, New York (41.0˚N, 73.91˚W) and began taking measurements in August 2023. A case study is presented that shows an aloft elevated O₃ layer around 4-5 km, which was observed by both O₃ lidars in NYC and Palisades NY, which is not associated with smoke plumes transport. A second case study shows O₃ exceedance (>70 ppb) within the planetary boundary layer at the LDEO site, which was about 20 ppb larger than in the urban area.