Coastal Boundary Layer Influence on Pollutant Transport in New England

Air pollution episodes in northern New England often are caused by transport of pollutants over water and involve two crossings of the coast. Two such episodes in the summer of 2002 are examined (22-23 July and 11-14 August). In both cases, the pollutants that affected coastal New Hampshire and coastal southwest Maine were transported over coastal waters in stable layers at the surface. These layers were at least intermittently turbulent but retained their chemical constituents. The lack of deposition or deep vertical mixing on the overwater trajectories meant that the pollutant concentrations remained strong. In the 22-23 July case, the trajectories were relatively straight and dominated by synoptic-scale effects, transporting pollution to the Maine coast. On 11-14 August, sea breezes brought polluted air from the coastal waters inland in New Hampshire, adding significantly to already strong concentrations transported and/or produced by other means.