TOPAZ Data

July 20, 2016

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Daily Summary:

Wednesday, July 20: CABOTS IOP2
Day 3 of CABOTS IOP 2 observations. TOPAZ data were taken from 09:50 to 21:50 PDT. Clear all day, with fair visibility in the morning (tops of the Sierra's clearly visible). High of about 36 C with winds veering from SE to SW in the morning, before rotating to the NW in the afternoon. The winds briefly shifted to the NNE between 19 and 20 PDT. The initial measurements showed high aerosol associated with the southerly flow in the shallow (300 m) BL in the morning with thinner layer near 1500 m. The first ozone measurements showed low concentrations (<40 ppbv) near the surface and higher values (70-90 ppbv) near 1.5 km. High ozone was also measured above 4 km all day. The ozone and aerosol layers near 1.5 km slowly descended as the CBL grew. Around 16 PDT the CBL appeared to completely entrain the descending ozone and aerosol layers and the surface concentations leveled off at about 60-65 ppbv. Ozone briefly increased to 70 ppbv when the winds shifted to the NNE around 19 PDT, then dropped rapidly to 30 ppbv when they rotated to the SSW. These changes are also visible in the lidar plot. Thw winds aloft also shifted to the NW around 20 PDT, leading to a sharp drop in ozone between 1 and 2 km.