Ozone Over the Coastal Ocean of Chesapeake Bay and New England

We have successfully deployed a new autonomous ozone measurement system for time-series measurements over the coastal ocean. Data were obtained at the Chesapeake Bay Lighthouse Tower (36.91 N, 75.71 W) for over a month in June-July 2003, and at an offshore tower at the Martha's Vineyard Coastal Observatory (41.32 N, 70.57 W) in late summer 2003. The data are compared with ozone and other data from nearby land stations. There is a strong correlation between ozone measurements at the coastal ocean towers and the land stations. However, the diurnal cycle is different over water, reflecting titration by NO emissions at night and increased dry deposition on land as well as differences in the atmospheric boundary layer structure over land and water. Back trajectories were calculated to determine the source regions of the air masses observed, and to examine differences in chemistry and transport between the land and ocean sites. A high-ozone pollution event in late June over the Chesapeake Bay region is analyzed in detail. These measurements are the beginning of a time series of ozone over the coastal ocean, and will be valuable in providing context to studies of air quality in coastal regions.