DISCUSSION 85 
these are well-defined levels in any sense of the 
word. They may vary by two degrees or per- 
haps even four degrees in temperature, because 
of beam-width effects. 
Dr. Swingle—Do I understand that, in fact, 
you have no observation of what the tempera- 
tures actually were in the cloud? 
Miss Ackerman—No, but the ‘preferred’ echo 
heights are very well separated. 
Dr. R. Wexler—Did you look for any relation- 
ship between the heights at which these first 
echoes appeared and the maximum height which 
was subsequently reached or in other words, for 
any relation at all between the region where the 
echo first appeared and the subsequent maximum 
development? 
Miss Ackerman—Yes, I tried to do so, using 
data for one day when there was a high fre- 
quency of echoes. I did not find any correlation. 
Dr. W. E. Howell—In a situation where you 
obviously hope in connection with some of these 
experiments to have a fairly repeatable cloud 
condition day after day, I wonder if it is not a 
little disturbing to find the pattern of echo varies 
so much from one day to another over these dif- 
ferent mountain ranges; and I wanted to ask if 
these had been related in your observations to 
the previous state of the ground, whether the 
previous occurrence of precipitation and con- 
sequent moistness of the ground affected the sub- 
sequent development on a later day. 
Miss Ackerman—No, they were not, and out- 
side of going into the radar data of each day, I 
do not know how we ean really do it. In the 
type of region we are talking about, there is not 
much rain and the rain comes in the form of 
scattered showers. We tried to see whether there 
was some correlation between the amount of 
rainfall reported by the existing stations with 
any of these data, but there was none. I really 
did not expect there to be, in view of the seat- 
tered nature of the echo areas and the sparseness 
of reporting stations. 
Dr. C. L. Hosler—Did you note any tendency 
of echoes when there were few echoes to reach 
greater heights than on the days when there 
were many? 
Miss Ackerman—No, I also thought this might 
be a possibility. 
Mr. Jerome Namias—A number of people 
seem to have suggested quite an ambitious re- 
search program for Miss Ackerman. In the geo- 
graphical area concerned, as you undoubtedly 
know, there is great precipitation sensitivity in 
the summertime depending on the location of the 
moist tongue. The gradient of moisture on both 
sides of this tongue is rather intense. Small 
shifts of the tongue will influence the whole syn- 
optic situation. Instead of working just with the 
Tucson radiosonde, I suggest plotting some isen- 
tropic charts to highlight this tongue and in this 
manner get an idea of the lateral mixing which 
could provide all sorts of variations even within 
six-hour periods. 
Miss Ackerman—As I said before, a real syn- 
optic analysis was not made, but it might be a 
good idea to do so. 
Dr. Mason—I think, Miss Ackerman should 
not be distressed that she can not get these 
things to tie up. This points to the difficulty of 
these problems even when one is dealing with 
everyday Cumulus. It also points out that if one 
uses one tool such as radar, this is very restric- 
tive. It only gives a very small part of the 
picture. We have to regard radar as one tool to 
be used in conjunction with a lot of others and 
these problems are very much more complicated 
than we thought at first. We have to go back 
and realize that Cumulus evolution is determined 
by the large-scale distribution of moisture, tem- 
perature, vertical motion, ete., right up the syn- 
optic scale, and the more of these data that 
point this out, the better it will be for long-term 
research in cloud physics. 
Miss Ackerman—Yes, I agree with you, and I 
am not particularly disturbed at not finding a 
simple explanation. We unquestionably have a 
complex situation. I would just like to repeat 
one comment made earlier by Dr. Byers; namely, 
the danger of taking one situation and develop- 
ing a general theory from it. In evaluating the 
data of seven days, we find seven different situ- 
ations. 
