had the lowest values as evidenced by the cumulative distributions
and were likely very representative of true ambient atmospheric
levels at the sites.
The dependence of field and ion levels on wind indicated that
corona activity on the ac conductors produced a localized downwind
enhancement of ambient atmospheric levels. However, the
magnitudes of the enhanced fields and ion concentrations exceeded
the range of upwind values only for a small percentage
of the time under most conditions. Maximum (99th percentile)
upwind (ambient) fields were exceeded less than 2 percent of
the time during downwind conditions at the NW and SE stations,
less than 11 percent of the time at the NE station and less