|Abstract or Summary
- The examination in some detail of the relationships between
air quality and the thermal structure of the lowest layers of the atmosphere
constituted the primary objective of this thesis. Data for
the study were assembled during April-June 1965 at the U.S.
Weather Bureau Station, McNary Field, Salem, Oregon. The measures
of air quality employed were the estimated mean concentrations
of suspended particulate material collected on standard high volume
filters near the surface during two six-hour periods each day : early
morning (0000 to 0600 L.S.T.) and afternoon (1200 to 1800 L.S.T.).
To represent thermal structure, lapse rates of temperature were
computed twice daily for each 150-meter-thick layer of air between
the surface and 1500 meters above the surface. The information for
these computations was taken from the original records of the U.S.
Weather Bureau radiosonde flights conducted daily at 0300 and 1500
L.S.T. Graphical and statistical analysis of the relationships between
lapse rate and air quality for each of the 150-meter-thick layers and
each of the cumulative layers (by 150 meter increments) originating
at the surface produced results that were quite different for the
morning and afternoon sampling periods. The relationships for the
morning period were determined graphically to be continuous and
determined statistically to be linear. For this period the stability of
the lowest 450 meters appeared to affect most directly the air quality
while the thermal structure above about 1000 meters appeared unrelated
to air quality. The afternoon relationships, on the other
hand, were poorly defined. In fact, the air quality of the afternoon
period was better related to the thermal structure of the early morning
period than to the contemporaneous thermal structure.
On the premise that for a given lapse rate, air quality may
fluctuate because of variations in pollutant emission rates and/or because
of changes in meteorological variables, supplementary studies
were conducted. The test procedure was the same for each variable,
and consisted of dividing the data for each sampling period into
classes of the parameter, then comparing the resulting relationships
both graphically and statistically with the combined relationships.
Surface wind velocities, average upper air wind speeds, prominent
synoptic features and air mass types, and the stability of the lowest
layers of the atmosphere prior to the beginning of the sampling periods were the meteorological parameters considered. Division
of data by weekend and work week, and then by day of the week was
also considered to assess possible variations of pollutant emission
rates over these periods. In no case did subdivision of data by additional
parameters produce any apparent increased information.
Since pilot balloon data are more numerous and less expensive
than corresponding radiosonde data, and since theory indicates that
wind shear may be a reasonable estimate of stability, the vertical
shears of the horizontal wind profiles of the lower atmosphere were
also compared with concurrent estimates of air quality. The relationships
between shear and air quality for both sampling periods
were judged both graphically and statistically to be poorly defined.
Although the development of relationships for the purposes of
estimating and predicting air quality was not an objective of this
study, many of the developed relationships between lapse rate and
air quality might be used for one of these purposes. In particular,
selected combinations of lapse rate of the morning period may be
used as an estimator of air quality for this period. Similarly, lapse
rate of the morning period might be utilized as a predictor of air
quality of the afternoon period.