What is coastal climate?

Historical definitions of what determines whether one lives in a coastal area or not have varied over time. According to Culliton (1998), a “coastal county” is defined as a county with at least 15% of its total land area located within a nation’s coastal watershed. This emphasizes the land areas within which water flows into the ocean or Great Lakes, but may be better suited for ecosystems or water quality research (Crowell et al. 2007). Some Federal Emergency Management Agency (FEMA) documents suggest that “coastal” includes shoreline-adjacent coastal counties, and perhaps even counties impacted by flooding from coastal storms. An accurate definition of “coastal” is critical in this regard since FEMA uses such definitions to revise and modernize their Flood Insurance Rate Maps (Crowell et al. 2007). A recent map published by the National Oceanic and Atmospheric Administration’s (NOAA) Coastal Services Center for the Coastal Change Analysis Program shows that the “coastal” boundary covers the entire state of New York and Michigan, while nearly all of South Carolina isconsidered “coastal.”The definition of “coastal” one chooses can have major implications, including a simple count of coastal populationand the influence of local or state coastal policies. There is, however, one aspect of defining what is “coastal” thathas often been overlooked; using atmospheric long-term climate variables to define the inland extent of the coastalzone. This definition, which incorporates temperature, precipitation, wind speed, and relative humidity, isfurthermore scalable and globally applicable - even in the face of shifting shorelines. A robust definition usingcommon climate variables should condense the large broad definition often associated with “coastal” such thatcompletely landlocked locations would no longer be considered “coastal.” Moreover, the resulting definition,“coastal climate” or “climatology of the coast”, will help coastal resource managers make better-informed decisionson a wide range of climatologically-influenced issues. The following sections outline the methodology employed toderive some new maps of coastal boundaries in the United States. (PDF contains 3 pages)

National Oceanographic and Atmospheric Administration

U.S. EPA Coastal Management Branch

U.S. Geolgocial Survey

NOAA Sea Grant