HR: 0830h
AN: A51D-0702    [PDF]
TI: Comparing Summer 2002 to the Decade-Long Air Quality Record at Harvard Forest: Patterns, Trends, and Anomalies.
AU: * Munger, J W
EM: jwm@io.harvard.edu
AF: Dept of Earth and Planetary Sciences Harvard University, 20 Oxford St., Cambridge, MA 02138 United States
AB: The Harvard Forest Environmental Measurement Site (EMS) was established in 1990 to quantify deposition of air pollutants to a forest canopy, to examine regional-scale rural air quality, and determine net carbon exchange by a typical New England forest. The measurement site is situated over a mile from the nearest paved road or building and major urban areas are over 100 km away. The observations from this site provide one of the best available records for establishing air quality patterns and trends in eastern North America. The focus of this talk will be $NO_{x}$, $NO_{y}$, $O_{3}$, and CO concentrations. Transport patterns and vertical mixing account for the dominant patterns observed in pollutant concentrations. Southwesterly winds at HF bring elevated concentrations of primary and secondary pollutants while northwesterly winds bring relatively clean background continental air. Emissions of $NO_{x}$ and CO accumulate beneath the nocturnal inversion and reactive species such as $O_{3}$ are depleted at the surface overnight. Variations in meteorological patterns from year to year complicate comparison of pollutant concentrations. We will make use of Stochastic Time-Inverted Lagrangian Trajectories to define periods that should be meteorologically similar. To establish the air quality context for observations during the NEAQS 2002 observation period we compare the probability distributions for pollutant concentration and mean diel cycles in the summer of 2002 with those from 1990-2001. The peak $O_{3}$ events during June-August 2002 were among the highest recorded at Harvard Forest, but clean air periods had some of the lowest $O_{3}$ concentrations. $NO_{y}$ concentrations at Harvard Forest tended to be lower across the entire concentration range and for both polluted and clean sector winds. CO concentrations during southwesterly winds were lower in 2002 relative to the typical range, but background concentrations were unchanged. A single event with forest-fire smoke from Quebec had maximum hourly CO concentrations exceeding 600 ppb. These concentrations exceed the peak values for the prior 11 years by over 50%.
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting