Effects of Meteorology on Air Pollution - Air Pollution and Global Warming: History, Science, and Solutions - page 143

Figure 6.4b. In summers, the Pacific high is sometimes
located to the northwest of the San Francisco Bay Area.
Under such conditions, air traveling clockwise around
the high passes through the Sacramento Valley, where
temperatures are hot and pollutant concentrations are
high, into the Bay Area, where temperatures are usu-
ally cooler and pollution also exists. The transport of
hot, polluted air from the Sacramento Valley increases
temperatures and pollution levels in the Bay Area.

smelter in Trail, British Columbia, Canada, released
pollution that traveled to Washington State in the United
States. This last case is an example of transbound-
ary air pollution ,which occurs when pollution crosses
political boundaries.
Sulfur dioxide emitted from tall smokestacks is often
carried long distances before it deposits to the ground
as sulfuric acid. Because most anthropogenic SO 2 (g)
is emitted in midlatitudes, where the prevailing near-
surface winds are southwesterly and the prevailing ele-
vated winds are westerly, SO 2 (g) is transported to the
northeast or east. If it is emitted at a high enough alti-
tude, SO 2 (g) can travel hundreds to thousands of kilo-
meters. The second largest smokestack in the world
(after the 419.7-m stack in the GRES-2 coal power
plant in Ekibastuz, Kazakhstan) is located in Sudbury ,
Ontario, Canada, north of Lake Huron. This nickel
smelting stack, which is 380 m tall, was built in 1972
and designed to carry SO 2 (g) and NO x (g) emissions far
from the local region. Although the stack reduced local
pollution levels substantially, it increased pollution in
all directions within 240 km of the plant, including to
the United States, causing devastation, particularly in
the prevailing wind direction.
Long-range transport affects not only pollutants emit-
ted from stacks, but also photochemical smog closer to
the ground. In 1987, Wisconsin believed that high mix-
ing ratios of ozone there were exacerbated by ozone
transport from Illinois and Indiana. Wisconsin then filed
alawsuit to force Illinois and Indiana to control pollu-
tant emissions better. The lawsuit led to a settlement
mandating a study of ozone transport pathways (Gerrit-
son, 1993).
Pollutants travel long distances along many other
well-documented pathways. Pollutants from New York
City, for example, travel to Mount Washington, New
Hampshire. Pollutants travel along the BoWash cor-
ridor between Boston and Washington, DC. Pollutants
from the northeast United States travel to the clean north
Atlantic Ocean (Liu et al., 1987; Dickerson et al., 1995;
Moody et al., 1996; Levy et al., 1997; Prados et al.,
1999). Pollutants from Los Angeles travel northward to
Santa Barbara, northeastward to the San Joaquin Valley,
southward to San Diego, and eastward to the Mojave
Desert. Such pollutants have also been traced to the
Grand Canyon, Arizona (Poulos and Pielke, 1994). Pol-
lutants from the San Francisco Bay Area spill into the
San Joaquin Valley through Altamont Pass.
An example of transboundary pollution is the trans-
port of forest fire smoke from Indonesia to six other
Asian countries in September 1997. Sulfur dioxide
emissions from China are also suspected of causing a

6.6.2.3. Santa Ana Winds
In autumn and winter, the Canadian high-pressure sys-
tem forms over the Great Basin, an elevated plateau, due
to cold surface temperatures. Winds around the high
flow clockwise down the Rocky Mountains, compress-
ing and warming adiabatically. The winds then travel
through Utah, New Mexico, Nevada, and into Southern
California. As the winds travel over the Mojave Desert,
they heat further and pick up desert soil dust. The winds
then reach the San Gabriel and San Bernardino Moun-
tains, which enclose the Los Angeles Basin. As winds
are compressed through Cajon Pass and Banning Pass,
two passes into the basin, they speed up to conserve
momentum (mass times velocity). The fast winds resus-
pend soil dust. The winds, called the Santa Ana winds ,
then enter the Los Angeles Basin, bringing dust with
them. If the winds are strong, they overpower the sea
breeze (which blows from ocean to land), clearing pol-
lution out of the basin to the ocean. Warm, dry, strong
Santa Ana winds are also responsible for spreading
brush fires in the basin. When the Santa Ana winds are
weak, they are countered by the sea breeze, resulting
in stagnation. Some of the heaviest air pollution events
in the Los Angeles Basin occur under weak Santa Ana
conditions. In such cases, pollution builds up over a
period of several days. Santa Ana winds are generally
strongest between October and December.

6.6.2.4. Long-Range Transport of Air Pollutants
Winds carry air pollution, sometimes over long dis-
tances. The chimney was developed centuries ago, not
only to lift pollution above the ground, but also to take
advantage of winds aloft that disperse pollution hori-
zontally. Chimneys exacerbate pollution downwind of
the point of emission. Starting in the seventeenth cen-
tury, for example, chimney emissions from the Besshi
copper mine and smelter on Shikoku Island, Japan,
vented pollution to agricultural fields downwind. In
the eighteenth century, smoke from soda ash factory
chimneys in France and Great Britain devastated nearby
countrysides (Chapter 10). In the 1930s to 1950s, a