May 26. Sunday. Clear and calm. Haze in the valley in the morning, but less so in the afternoon.  Lidar data was collected from 1155 to 2335 PDT.  The preliminary TOPAZ curtain plot shows much lower O3 concentrations at the beginning of the run in agreement with the model forecasts.  The in situ O3/CO measurements decreased gradually from 65/133 ppbv at 1033 PDT to 55/106 ppbv at 1905 PDT.  The concentrations then remained constant until the end of the run at 2345 PDT.  Two elevated O3 layers of presumed stratospheric origin appeared above 2 km ASL at about 1600 PDT with the lower one descending slowly over the next several hours.
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Note: the low (purple) ozone values seen near the top of the curtain plot near midday are biased by the solar background in these preliminary analyses.