Page 6 - nlf1954smog

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SMOG - THE TRIGGER

It must be remembered that on many days or the year, the 1,500
·tons per day of organic effluents put into the air or Los Angeles cause
little or no trouble. The only time when these pollutants build up to
intolerable 'proportions are on those days (usually in late Summer and
Fall) when weather corditions conspir6 to trap the materials over the oityo

In the Summer and Fall, Los Aneeles experiences frequent and
long "inversions"o A temperature inversion consists of a layer or warm air,
suspended at some distance above the groum, that prevents the usual air
turbulence. Such an inversion at a heieht of 1,000 tt. or less over Los Angelea,
will effectively seal in the air contaminants, since the wall of mountain
surrourxUng the city will not permit the polluted air to escape from under
the inversiono Over the Los Angeles basin a severe, low inversion may
persist for many days, even a week or two. When this happens, the build-
up of pollutants reaches truly intolerable levels, such as during Thanks-
giving week of this y~,ar, when there were tr~ousands of traffic accidents
because of poor visibility, air traffic was grounded, crops damaged, and
severe eye irritation experienoede

The inversions that form over the Los Angeles Basin have their
origin over the Pacific Ocean and extend over Newhall as wello The F,astern
Santa Clara Basin is much smaller however, and farther inlando With a.
lareer proportion of mountainside to air volume, and with a wider daily
fluctuation in temperature, we pet a greater turbulence during the day
which serves to destroy the inversion or at least raise it high enough to
permit dilution and escape of any pollutants that might be presento Thus,
although our nighttime inversion will be as severe (and possibly a little
more so) than Los Anv,eles will have, this will be completely or partially
broken up duri~ the day, with the result that we do not have the problem
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of coping with the build-up of many days production of air pollutantso