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  • Author or Editor: W. H. Hoecker Jr. x
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J. K. Angell, C. R. Dickson, and W. H. Hoecker Jr.

Abstract

The Los Angeles Reactive Pollutant Project (LARPP) in the autumn of 1973 involved helicopter sampling of a volume of air “tagged” by means of three constant volume balloons (tetroons) released simultaneously from a point on the ground. Based on radar tracking of 35 tetroon triads at a mean height of 350 m above sea level, this paper considers the estimates of relative diffusion obtained from the rate of separation of the tetroons making up the triad. In the average, the median lateral standard deviation of tetroon position varies from 90 m after a travel time of 15 min to 800 m after 2 h, and from 140 m at a travel distance of 2 km to 1000 m at 20 km. The relative diffusion is indicated to be nearly twice as large in “neutral” as in “stable” conditions. Comparison with the results obtained by other investigators in other locations shows that the relative diffusion within the Los Angeles Basin is frequently unusually small, particularly with respect to travel time.

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J. K. Angell, C. R. Dickson, and W. H. Hoecker Jr.

Abstract

Tetroon trajectories within the Los Angeles Basin in the autumn of 1973 show that, on non-stagnation days, air located in the Los Angeles area in the morning can pass over the Puente Hills and reach the San Bernardino-Riverside area by mid-afternoon of the same day. However, the enhanced vertical mixing associated with these Hills would be expected to dilute any pollution present. Of perhaps more importance is the evidence that, on stagnation days when the atmosphere is stable, air from the Los Angeles area may drift southward in the early morning katabatic flow, stagnate for 2–3 h in the industrialized and high vehicle-density region north of Long Beach, and then move rapidly eastward with the sea breeze flow through Santa Ana Canyon, reaching the Riverside-San Bernardino area in late afternoon. In this case there would seem to be more potential for severe pollution in the latter area. However, the frequency of occurrence of this particular trajectory pattern is uncertain.

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