ice fog (from water vapor that is emitted and freezes), which raises the inversion height, help prevent accumulation of high ambient CO concentrations. The current problem with high ambient CO concentrations tends to occur (five out of the last six exceedances of the 8-h National Ambient Air Quality Standard [NAAQS]) at temperatures of roughly 0–20°F, when ice fog is not present and the use of engine-block heaters is not necessary for starting.

This chapter discusses the CO problem in Fairbanks, beginning with the physical and demographic characteristics of the area; the management strategies used to control the CO problem; and a simple air quality model for coupling meteorology and vehicle emissions. Lessons learned from the Fairbanks case are summarized in the committee’s findings and recommendations in the Summary of this interim report and serve as a basis for the development of a final report that will include assessments of other CO problem areas. The specific health effects of exposure to CO in Fairbanks are not discussed, because no human exposure or epidemiological data were available.

GEOGRAPHICAL, METEOROLOGICAL, AND SOCIETAL CONTEXT

Physical Setting

Fairbanks is in a floodplain on the north shore of the Tanana River, just upstream of its confluence with the Chena River. The city is open to the south and southeast, with a very gradual slope in that general direction from the Tanana River up to the foothills of the Alaska Range, some 75 km away. To the west and north, residential areas extend into the Yukon-Tanana uplands a few hundred meters above the city. Level ground extends some 35 km to the east except for Birch Hill northeast of town. Figure 2–1 shows a topographical representation of Fairbanks and the surrounding area.

The meteorology is fairly typical of interior Alaska and other continental high latitudes. In the typical winter pattern, anticyclones (high-pressure systems), weak lows, and other weak pressure fields dominate the weather, all with moderate windspeeds. Strong pressure gradients and cyclonic (low-pressure) systems are unusual in winter. For 1996 through 2001, all exceedances of the 8-h CO health standard in Fairbanks have occurred with southeasterly winds aloft. These winds, which travel over the Alaska Range, are associated with counterclockwise geostrophic flow around a low-pressure system in or near the Gulf of Alaska.



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