Coordinated profiling of stratospheric intrusions and transported pollution by the Tropospheric Ozone Lidar Network (TOLNet) and NASA Alpha Jet experiment (AJAX): Observations and comparison to HYSPLIT, RAQMS, and FLEXPART

Response to Reviewer 1

“…The identification of stratospheric intrusions is typically quantified using tracers of stratospheric origin in numerical models. On this basis, seven stratospheric O 3 intrusions occurred in the western United States during the IONS2010 campaign in May-June 2010 (Cooper et al, 2011;Lin et al, 2012a, b). The four strongest intrusions occurred on 22-24 May, 27-29 May, 7-8 June and 9-14 June (Lin et al, 2012a, b).…”

“…On this basis, seven stratospheric O 3 intrusions occurred in the western United States during the IONS2010 campaign in May-June 2010 (Cooper et al, 2011;Lin et al, 2012a, b). The four strongest intrusions occurred on 22-24 May, 27-29 May, 7-8 June and 9-14 June (Lin et al, 2012a, b). Enhanced ozone mixing ratios in combination with very low relative humidity (RH) provides a qualitative proxy for dry air of possible stratospheric origin.…”

A fully autonomous ozone, aerosol and nighttime water vapor lidar: a synergistic approach to profiling the atmosphere in the Canadian oil sands region

“…Stratospheric intrusions were frequently observed throughout the year, with sometimes three or four occurrences per week. In recent years, there has been more understanding about the mechanism that enables these STT events (Langford et al, 2018). However, there is still very little data on the frequency and magnitude of these events and their impact on the tropospheric ozone budget.…”

“…Ozone is a short-lived climate pollutant (SLCP) and air pollutant that can have detrimental impacts on human health (Malley et al, 2015;Lippmann, 1991), agriculture (McKee, 1994) and ecosystems (Ashmore, 2005) when present at high enough concentrations. Tropospheric ozone is photochemically produced primarily from nitrogen oxides and volatile organic compounds (VOCs) from anthropogenic sources, is biogenically produced from forest fires (Aggarwal et al, 2018;Trickl et al, 2015) and can be enhanced through stratospheric/tropospheric transport (STT) events (Ancellet et al, 1991;Langford et al, 1996;Leblanc et al, 2011;Stohl and Trickl, 1999). Both of these latter sources can have significant impacts on ozone concentration although typically their impacts vary within the vertical distribution of the troposphere.…”

“…For details of the intercomparison refer to a separate publication (manuscript in preparation). Lidar networks (http://ndacc-lidar.org, last access: 14 November 2018; http://mplnet.gsfc.nasa.gov, last access: 14 November 2018; Papayannis et al, 2008;Sugimoto and Uno, 2009) are very important scientific tools that allow the collective benefit of increased geographical coverage (Langford et al, 2018;Trickl et al, 2016) and can often provide valuable climatological data (Granados-Muñoz and Leblanc, 2016;Khaykin et al, 2017;Gaudel et al, 2015). The existence of networks like TOLNet will help to address the need for more ozone profilers in the troposphere as reported in the recent Tropospheric Ozone Assessment Report (TOAR) by Gaudel et al (2018).…”