FAST-LVOS 2017 TOPAZ Data

June 22, 2017

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Daily Summary:

Thursday, June 22
TOPAZ data were recorded from 09:10 - 20:14 PDT. Another extremely hot day (max. of 45 C at the lidar site) and 113 F at the NLVA NWS tower. Very clear with only a very few clouds over the mountains. The winds were light during most of the day, shifting from northwesterly downslope flow to very weak southerly flow around 0900 PDT. The elevated smoke layer seen the previous two days was mostly gone, with only two thin and weak aerosol layers (but no ozone) remaining near 4 and 5 km agl. A thin, but much more concentrated aerosol layer was present at the surface in the morning. Ozone began to increase early in the lowest 1 km, rising from about 50 to more than 80 ppbv between 0900 and 1100 PDT. Another layer of enhanced ozone and aerosol was present between 2.5 and 3 km agl and intensified around 1100 PDT. Surface O3, CO, and CH4 began increasing at AP around the same time, and HYSPLIT back trajectories suggest that this layer originated from the Holcomb Fire near Big Bear Lake although there was no obvious smoke associated with the fire plume. This layer was entrained by the growing mixed layer between 1300 and 1400 PDT, contributing to the high surface ozone. The surface and ML column O3 decreased around 1500 PDT as the growing ML entrained lower O3 air from above 3 km agl. A brief shift in the surface winds to the north caused a short-lived drop in the O3 and aerosol concentrations below 1 km around 1600 PDT, but the concentrations recovered and the ML grew to more than 4 km agl. Ozone fell to about 60 ppbv throughout the column after the winds shifted to the west and increased to more than 10 m/s around 1800 PDT. The MDA8 was greater than 75 ppbv at the TOPAZ truck, and reached values of 77, 73, 73, and 70 at the Joe Neal, Palo Verde, Walter Johnson, and Apex monitoring sites, respectively.