Managing Carbon Monoxide Pollution in Meteorological and Topographical Problem Areas (2003) / Chapter Skim
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2. Contributions of Topography, Meteorology, and Human Activity to Carbon Monoxide Concentrations
2. Contributions of Topography, Meteorology, and Human Activity to Carbon Monoxide Concentrations
Pages 72-99
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From page 72... ...
The chapter concludes with illustrative examples of the factors contributing to the CO problems in CaTexico, California; Lynwood, California; Fairbanks, Alaska; Las Vegas, Nevada; and Denver, Colorado.
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From page 73... ...
Because water vapor is an important greenhouse gas (infrared radiation from the earth's surface is absorbedby wafer molecules end reradiated beck down, warming the surface) , reduced water vapor allows infrared radiation to pass into space, producing ground level temperature inversions after sundowns and lower mixing heights.
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From page 74... ...
Horizontal advection of warm air creates a high-altitude inversion and can similarly increase the stable temperature stratification aloft (Figure 2-l[b]
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From page 76... ...
+20 FIGURE 2-2 Schematic of how an existing surface-based inversion (solid lined can be strengthened by subsidence (dashed lined or by advection of warm air aloft (dotted line)
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From page 77... ...
Figure 2-3 illustrates air stagnation in a trapping valley. Influence of Topography on Meteorological Conditions Pielke (2002)
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From page 78... ...
thermally driven winds are independent ofthe above-valley winds and are controlled by locally developed valley pressure gradients; (2) downward momentum transport ofthe above valley winds (as is associated with a deep convective boundary layer)
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From page 79... ...
nocturnal drainage flow and (b) upslope flow with no prevailing synoptic flow, with an input condition typical of summer in midlatitudes.
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.. i E S W N ~ £ ~ W ~ THERMALLY DRIVEN DOWNWARD MOMENTUM TRANSPORT FORCED CHANNELING PRESSURE DRIVEN CHANNELING FIGURE 2-5 Relationships between above-valley (geostrophic)
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From page 81... ...
It is not known, however, what fraction of nonexceedance days has such meteorological conditions or how many of the exceedance days before 1996 had these conditions. Nonetheless, the surface pressure gradient observed during all six exceedances from 1996 to 2001 must have some significance.
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From page 82... ...
Fairbanks exhibits the maximum number of exceedances in January. The considerably greater numbers of exceedance days in Fairbanks in January compared with November, and in February compared with October, are attributed to reduced cloud cover in the winter months compared with the autumn months.5 Clear skies in January and February contribute month.
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From page 83... ...
Feb March April May June FIGURE 2-7 Number of days with exceedances of the 8-hour CO standard by month in Fairbanks, Alaska, between July 1972 and June 2001. Numbers include days on which exceedances occured at any of the three monitoring sites.
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From page 84... ...
The numbers include days on which exceedances occurred at any of the Tree monitoring sites. Source: Data provided by Paul Rossow, Fairbanks Norm Star Borough.
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From page 85... ...
The very deep minima in Las Vegas and Calexico in the early afternoon suggest that solar heating at these southern latitudes is able to disperse the CO effectively at that time of day. (To verify that low afternoon CO concentrations are due to meteorology rather than to very Tow afternoon emissions would require an analysis of traffic flownear the monitors.)
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From page 86... ...
and maximum (light line) 1-hour CO concentrations at monitoring sites listed in Table 1-1 for 85 nonholiday weekdays during the winter (November through February)
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From page 87... ...
Contributions of Topography, Meteorology, and Human Activity 87 it,= .
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From page 88... ...
, and in some cases transport in from surrounding areas. Simulations of the six most recent exceedance days in Fairbanks (five of which occurred in February)
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From page 89... ...
The highest and second-highest daily average CO values for that winter occurred on Tuesday, February 8, 2000, and on Monday, November 19, 1999. Both were exceedance days, 9This mean (0.08)
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From page 90... ...
9o To to to .= 3 .= z ~ .> ~ ~ ·Ct o ~ Ct Ct · I o Cal A au o ~ ~ Oo ~ ~ o 0 Go ~ ~ Go _ ~ ~ ~ _ o Ct ~ .
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From page 91... ...
The daily average traffic was obtained by diving the total traffic count each day by 24 hours. with maximum 8-hour average CO values of 11.5 ppm and 11.2 ppm, respectively.
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From page 92... ...
Data were provided by Paul Rossow ofthe Fairbanks North Star Borough.
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From page 93... ...
Variability in meteorological conditions, such as strong temperature inversions or winds blowing from the direction of nearby communities with high levels of CO, contributes to these difficulties. The status of problem areas could fluctuate between attainment and nonattainment until further emissions reductions provide an adequate safety margin.
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From page 94... ...
To reduce vulnerability, emissions reductions must extend beyond the attainment threshold to provide an adequate safety margin. ILLUSTRATIVE EXAMPLES This last section provides five illustrative examples of locations that have had problems meeting the NAAQS for CO.
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From page 95... ...
Further analysis is needed to assess the relative roles of cross-border transport of vehicles operating in MexicaTi compared with vehicles idling at the border in producing CO. To address the problem of cross-border air polluTithe population ofthe Fairbanks North Star Borough, with a much larger area of about 7,000 square miles, was 82,840 in 2000 (U.S.
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From page 96... ...
The study concluded that significant CO emissions originating in the Lynwood area are added to an urban air mass with high CO concentrations that is transported into the Lynwood area. These emissions sources combine with stable nighttime meteorological conditions to create high CO concentrations in Lynwood.
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From page 97... ...
Las Vegas, Nevada Las Vegas is a rapidly growing city in southern Nevada that had a population of nearly 41 S,000 in 1999, up from about 260,000 in 1990 (U.S. Census Bureau 2000c)
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From page 98... ...
Las Vegas undertook a significant CO saturation study to help assess the monitoring network and movement of CO (Ransel 20021. The study extensively augmented the 14 permanent monitoring sites with 63 temporary fixed sites and mobile sampling at over 2,500 locations.
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From page 99... ...
associated elevated CO concentrations with winds at less than 1 MPH and an effective mixed layer less than 25 to 50 m that lasts for at least 3 hours.
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