PPT Slide
Notes:
Routine ozone measurements alone can often provide strong empirical evidence of transport - for example along the coast of Maine during the July 20-22, 1994 episode.
Concentrations in excess of the 80 ppb Maine State Standard were recorded at all of these coastal sites, four of which also recorded exceedances of the federal standard. With persistent southwesterly winds throughout the day, the hour of maximum concentration occurs progressively later in the day as one moves to the northeast, ranging from 12 noon at Lynn, MA to as late as 9pm at Jonesport, ME.
It seems that there are times during the ozone season where one could actually set their watch to the hourly progression of these transported plumes migrating down the coast of Maine. The NE-ward movement is not the only force at hand; coastal sea breezes that seem to elude many of the advanced meteorological models play a very important role in re-introducing off-shore plumes into coastal locations in Maine. Many of Maine’s most significant episodes are driven by these E/SE to W/NW flow patterns that become active in the afternoon when the onshore winds become active.
Note: Several of the following images are reproduced from, and are discussed in additional detail in a NESCAUM report entitled “Preview of 1994 Ozone Precursors in the Northeastern US”, available at:
http://capita.wustl.edu/nescaum/Reports/PAMS94/nepams_c.html