Mesoscale meteorology of the New England coast, Gulf of Maine, and Nova Scotia: Overview

Abstract

The North Atlantic Regional Experiment (NARE) domain includes the coastal and near‐coastal areas of New England and Atlantic Canada, and the intervening Gulf of Maine. This area has a complex coastline on all scales. The meteorology of the region is affected by the contrasting properties of the land and ocean, especially the temperature contrast. This paper reviews the knowledge of coastal meteorology on scales from tens of meters to 100 km, emphasizing those processes that most strongly affect pollutant transport in the NARE area in summertime. Examples from the NARE 1993 Summer Intensive measurements and modeling studies are used to illustrate these processes. The understanding and interpretation of regional and global air quality measurements depend on meteorological information about such issues as the amount and location of vertical mixing, the three‐dimensional trajectories of air parcels, the prevalence and scale of stratification, the speed of horizontal transport, and the scale of horizontal homogeneity or inhomogeneity. These issues are among those not fully understood in the complex coastal environment. From what is known, and from the NARE measurements, we can draw some conclusions. Polluted air from the U.S. East Coast transported over the Gulf of Maine becomes stably stratified, and vertical mixing is limited. The scale of vertical layering may be a few tens of meters or less. Layers separated by a few hundred meters in the vertical over Nova Scotia may have crossed the U.S. coast at points hundreds of kilometers apart. Wind speeds and directions, and therefore transport times, may differ substantially between the layers. Air at the surface may be isolated from, and have drastically different chemical contents from, air at only a few hundred meters above the surface.