In Medford, Oregon, the major source of pollution is the lumber
mill waste burner. Its low combustion efficiency results in the
emission of large quantities of particulate into the atmosphere.
Due to the influence of the atmospheric radiation inversion and
possibly the poor performance of the burners at the time of start-up,
concentrations of particulate were found to be highest in the morning.
Correlating these morning concentrations with average surface relative
humidity, average surface wind speed, and various stability indices,
most of which were determined from the U.S. Weather Bureau's
0300 PST radiosonde release, provided a measure of the degree of
relationship between these meteorological factors and pollution. In
addition, the analysis resulted in a determination of what stability
factors could readily be used to predict pollution concentrations with
reasonable accuracy (correlation coefficients ≥ 0.65). These included
the sounding energy to 850 mb (energy required to lift a parcel of air from surface to 850 mb), the temperature difference index
(difference in temperature between 850 mb and surface), the Modified
Showalter Stability Index (Showalter Index applied to the layer of
air between surface and 850 mb), and the persistence index (the sum
of three weighted Modified Showalter Index values for three consecutive
mornings).
Graphical and regression prediction models involving the persistence
index and average surface wind speed were developed. These
relationships proved to be more accurate in predicting morning concentrations
of particulate (multiple correlation coefficients 0.84)
than those involving only one meteorological variable (highest correlation
coefficient = 0.74).
In order to illustrate the effects of air pollution on visibility, a
preliminary relationship between concentrations of suspended particulate
and visibility was developed. If visibility were selected as the
criterion for judging air quality as it might well be in a tourist-oriented economy, such a relationship could serve as the basis for
forecasting conditions of unacceptably low visibility as a result of
high concentrations
