Sunday, June 18
<br>
TOPAZ data were recorded from 09:24 - 19:08 PDT. Extremely hot (max. of 46 C at the lidar site). Shallow Cumulus over the nearby mountain ranges in the afternoon. Light winds that followed the diurnal flow pattern. Overnight, clean marine air had been advected into southern Nevada, which decreased ozone concentrations to below 40 ppbv in the lower troposphere. TOPAZ observed a layer with moderate aerosol concentrations and 45-50 ppbv ozone between 3 and 5 km AGL. Local production caused a late increase of surface ozone, which peaked at 53 ppbv around 1800 PDT.