584
KRUGER, HOSLER, AND MILLER
coast near Stanford, Calif. Final evaluations of these studies will be
reported as each is completed.
Collections were made during two severe storms in May 1963 in °
Oklahoma, These collections were originally made as part of our study
of convective activity and
1 conjunction with objectives of Project
Springfield.* Preliminary analysis of the radiochemical and meteorological data shows surprising results with respect to convective activity.
These storms will be the subject of a separate report.
Two extratropical cyclonic storms were sampled at State College,
Pa,, during November 1962 and March 1963. These storms occurred
after the cessation of atmospheric nuclear-weapons detonations. They
are also being studied separately because of the unusual interest
aroused by their having debris age changes that occurred during the
storm periods,
The report presented here discusses the studies of precipitation
from extratropical cyclones and from showers and thunderstorms,
CONVECTIVE ACTIVITY
Introduction
Initial studies’ of large-scale-uplift systems showed that *’Sr con-
centration in precipitation where drop sizes are small was dependent
upon the experience of the precipitation in falling from the base of the
clouds to the ground, For large-scale-uplift systems, the height of the
generating level and the nucleation process may be relatively constant
over periods of several hours, With lateral uniformity of water content
and *0Sr-bearing nucleating particles throughout a given air mass, the
extent of growth of raindrops by accretion in the cloud and evaporation
below the cloud thus is determined primarily by the height of the
ceiling.
For convective activity, vertical motions within individual cells are
greatly enhanced relative to large-scale uplift, and several parameters
simultaneously affect the ground-level "Sr concentration. Precipitation
originates from rapidly varying heights during the life cycle of an
individual convective cell. Variations may also occurin the precipitation-generating process, in the drop sizes, in the Sr-bearing particu-
late air concentrations, and in the water content of the cloud.
*Project Springfield is the code name for a special atmospheric-sciences
research project funded by the Defense Atomic Support Agency and the U. S.
Atomic Energy Commission in cooperation with the U. 5. Weather Bureau and
several universities and industrial groups. This project has as its goal the
documentation of the spring-fallout maximum by use of aircraft sampling and
intensive measurements and radioanalysis of rainfall.