Saturday, May 20
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TOPAZ data were taken from 10:25 - 18:09 PDT. Seasonal temperatures with a high around 33 C, light winds. The high-ozone layer that had been observed the previous three days thinned further and contained less ozone (~ 80 ppbv). It lowered to about 2.5 km AGL by 14:00 PDT and then most likely moved away from the Las Vegas area. The mixed layer was not deep enough to entrain this ozone layer. Surface and BL ozone peaked in the low 60s ppbv in the afternoon.