Improving Estimates of Entrainment Mixing, Subsidence, and Photochemical Ozone Production using Aircraft and Ozone lidar during the California Baseline Ozone Transport Study (CABOTS)

In situ flight data collected in the San Joaquin Valley of California during the summer of 2016 is used to measure entrainment rates, ozone photochemical production, and regional methane and NOx emissions. The San Joaquin Valley is plagued with air quality issues including a high frequency of ozone exceedances in the summer and an aerosol issue in the winter exacerbated by a complex meso-scale environment. The flights were conducted during the California Baseline Ozone Transport Study (CABOTS), and span the valley between the cities of Fresno and Visalia with a thorough probing of the atmospheric boundary layer (ABL) including vertical profiling to diagnose the growth rate and horizontal gradients in ABL height. Entrainment velocities, which are the parameterized mixing of free tropospheric air into the boundary layer, are determined by a detailed budget equation of the inversion height. Subsidence, which is essential to our determination of entrainment velocity, is diagnosed by way of descending ozone laminae in the region above the ABL. The subsiding laminae are located within the flight data and corroborated by the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) lidar measurements in Visalia. A novel scalar budgeting technique is then applied to expose residual terms of individual equations that amount to ozone photochemical production and emission rates. The budget equations are closed by our estimated entrainment velocities, in conjunction with the time rates of change (storage) and horizontal advection all determined via flight data.