Intercomparison of lidar, aircraft, and surface ozone measurements in the San Joaquin Valley during the California Baseline Ozone Transport Study (CABOTS)

Abstract

Abstract. The California Baseline Ozone Transport Study (CABOTS) was conducted in the late spring and summer of 2016 to investigate the influence of long-range transport and stratospheric intrusions on surface ozone (O3) concentrations in California with emphasis on the San Joaquin Valley (SJV), one of two extreme ozone non-attainment areas in the U.S. One of the major objectives of CABOTS was to characterize the vertical distribution of O3 and aerosols above the SJV to aid in the identification of elevated transport layers and assess their surface impacts. To this end, the NOAA Earth System Research Laboratory (ESRL) deployed the Tunable Optical Profiler for Aerosol and oZone (TOPAZ) mobile lidar to the Visalia Municipal Airport (36.315° N, −119.392° E) in the central SJV between 27 May and 7 August 2016. Here we compare the TOPAZ ozone and backscatter measurements with co-located in-situ surface measurements and nearby regulatory monitors, and to airborne measurements from the University of California at Davis/Scientific Aviation Mooney and NASA Alpha Jet Atmospheric eXperiment (AJAX) research aircraft. Our analysis shows excellent agreement between the lidar and in-situ measurements, lending confidence to the use of these data sets for more detailed analyses.

Ozone Production in the Soberanes Smoke Haze: Implications for Air Quality in the San Joaquin Valley During the California Baseline Ozone Transport Study

“…This indicates that most of the smoke became fairly uniformly distributed above the central and southern SJVAB, although the spikiness in late July shows that finer scale plumes were still reaching the eastern valley. Regressions between the Fresno and Bakersfield AODs and the TOPAZ integrated backscatter imply extinction‐to‐backscatter ratios of S = 39.6 ± 0.6 sr ( R = 0.77) and 36.9 ± 0.4 sr ( R = 0.81), respectively, comparable to the value assumed in the lidar retrievals (Langford et al, 2019).…”

“…The individual points in these plots represent samples taken between 1,500 and 2,500 m asl at roughly 100‐ to 200‐m intervals and include both buffer layer and free tropospheric samples. The reasonable agreement between the lidar and aircraft O 3 measurements in the top row lends confidence to the assumption that the lidar and aircraft were sampling similar air masses on all 3 days; more rigorous intercomparisons are described elsewhere (Langford et al, 2019). The middle panels (Figures 13d–13f) show that the OPRs (relative to CH 4 ) estimated from these sparsely sampled measurements are similar to those derived from the more complete plume analyses in Figure 12f.…”

“…The afternoon flights included low approaches and/or spiral profiles at the VMA for comparisons with TOPAZ and the in situ surface measurements at the VMA. The aircraft, lidar, and in situ measurements of O 3 agreed to within ±5 ppbv on average during these comparisons (Langford et al, 2019).…”

“…A second wing pod carried a nonresonant laser‐induced fluorescence instrument to measure formaldehyde (CH 2 O) (St. Clair et al, 2017). The AJAX O 3 measurements were also compared with TOPAZ during profiles and low approaches at the VMA before the start of the Soberanes Fire, and these comparisons likewise found agreement to within ±5 ppbv (Langford et al, 2019). AJAX also sampled the Soberanes plume on several flights conducted after the end of the CABOTS campaign that will not be discussed here.…”

“…Ozone, CO 2 , CH 4 , and other species were also sampled by single‐engine Mooney TLS Bravo and Ovation 2 research aircraft operated by the University of California, Davis (UC Davis) and Scientific Aviation (SciAv) (Trousdell et al, 2019) and by the NASA Alpha Jet Atmospheric eXperiment (AJAX) research aircraft (Yates et al, 2015). Details of the sampling techniques and intercomparisons between the lidar and airborne O 3 measurements are described in Leblanc et al (2018) and Langford et al (2019).…”