The measurements indicate the presence of residual [O.sub.3] layering at the inland site (LaRC) above 1500 and 500 m in the marine environment (CBBT).
In the marine environment at CBBT, lower-level (100-300 m AGL) winds are very light (<1 m [s.sup.-1]), indicating general stagnation in this altitude region over the lower Chesapeake Bay.
The first vehicle remained near LaRC to sample continental [O.sub.3] variability, while the second traveled south and eastward from LaRC to approach the CBBT site and the bull's-eye feature predicted in the forecast.
The UAV flights, which were supported by the LaRC Autonomy Incubator team and UAV Operations Office, were able to sample vertically to an altitude up to 100 and 200 m at LaRC and CBBT, respectively, and horizontally within visual range.
Since large shipping vessels frequently passed between the third and fourth islands of the CBBT, the location served as an effective vantage point for directly sampling ship-based emissions.
Peak [O.sub.3] concentrations near 70 ppbv were recorded as the vessel approached the CBBT site near 1430 LT, providing direct evidence of a polluted Overwater [O.sub.3] reservoir.
The aircraft included a diverse chemical sensor suite (Table 1) and performed a flight pattern that included spirals over LaRC and CBBT and low-altitude passes from land to water.