xil PREFACE 
background information to the scope of the Conference: Essenwanger discusses the 
possibilities of a physical interpretation of frequency distributions of precipitation, 
Volz shows what the rainbow can tell about oscillations in freely falling raindrops, 
and the papers by Vonnegut and Moore discuss the always stimulating problems of 
precipitation and atmospheric electricity. 
The reader is also referred to the extremely interesting session on Artificzal Pre- 
cipitation Control (papers by Orville, Singer, Dessens, Todd, Battan and Kassander, 
Howell, and Semonin) which was one of the highlights of the Conference not only 
on account of the stimulating scheduled papers but also on account of the inspiring 
discussions. While it is impossible to do justice to the various new ideas and concepts 
that evolved in this session, this appears to be the place to recall the suggestion, 
made repeatedly by the Honorary Chairman throughout the Conference, to include 
in the evaluation of cloud physics or weather-radar projects a good synoptic analysis 
of the corresponding weather situations. We feel that this suggestion is of special 
significance in the evaluation of rainmaking or weather-control experiments into 
which statistical methods have entered deeply. It was therefore refreshing to find 
that such work is already well underway in the physical evaluation of seeding activi- 
ties in Santa Barbara, California. Indeed, these investigations will lay the ground 
work for a new phase in the design and evaluation of seeding experiments which will 
be greatly superior to and finally end the era where design and evaluation of such 
experiments were governed by statistical methods only. 
It is of necessity that all problems discussed in this Conference are still more or 
less in the basic-research state; and that they cannot as yet be applied to the chief 
objective of meteorology, namely towards improving weather forecasts in general 
and precipitation forecast in particular. The fact, however, that the discussions were 
not only inspired by the participating cloud physicists, but also, and sometimes even 
more so, by the scientists working in synoptic meteorology and numerical forecasting 
methods indicates that a most valuable cross fertilization between cloud physics and 
synoptic meteorology is underway and was achieved to a high degree during this 
Conference. 
The Editor, as Chairman of the Cloud Physics Committee, acknowledges the 
splendid support and assistance given to him by the Committee on Cloud Physics, 
namely, Charles E. Anderson, Roscoe R. Braham, Jr., Dwight B. Kline, J. KE. 
MeDonald, Joanne 8. Malkus, and Vincent J. Schaefer. 
Dr. Helmut Weickmann, Editor 
Chairman, Cloud Physics Committee 
American Geophysical Union 
Asbury Park, N. J. 
December 1959 
