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U.S. Department of Energy
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Diurnal and elevational variations in ozone and aerosol concentrations in New Hampshire`s Class-I Airsheds

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OSTI ID:197435
 [1];  [2]
  1. Appalachian Mountain Club, Gorham, NH (United States)
  2. Harvard School of Public Health, Boston, MA (United States)
Ozone and fine mass aerosol concentrations on New Hampshire`s Mount Washington, situated adjacent to both the Presidential/Dry River and Great Gulf Wilderness Class-I Airsheds, exhibit distinct diurnal and elevational patterns. These patterns are attributed to regional pollutant transport dynamics, nocturnal atmospheric stratification, mountain meteorological phenomena and scavenging. A well-defined planetary boundary layer (PBL) forms at about 1 km elevation at night as demonstrated by nocturnal ozone monitoring along the Mount Washington Auto Road. The PBL provides an effective elevational barrier at night, isolating the valleys from the regionally transported air pollutants present above the mixing layer. During the daytime, the PBL breaks up due to convective processes and katabatic winds resulting from solar heating in the valley. This process creates a diurnal mixing cycle with ozone maxima recorded near mid-day in the adjacent valley. In contrast, fine mass concentrations are higher at the valley site, attributed to local source inputs, and the lack of strong nocturnal scavenging processes, compared with ozone. How aerosol concentrations are related to the PBL and how they are affected by diurnal mixing remains unclear largely due to current sampling methods. Exposure to ozone is generally greater above the treeline in the two airsheds.
OSTI ID:
197435
Report Number(s):
CONF-9405167--
Country of Publication:
United States
Language:
English