BEHAVIOR PATTERNS OF NEW ENGLAND HAILSTORMS 355 
rors in echo height and intensity measurement 
have been discussed by Donaldson [1959]. 
Echo top heights and temperatures—All thun- 
derstorm echo top heights measured during 1956 
and 1957, plus a few from 1958, were classified 
according to the largest hail size reported within 
ten minutes before or after the radar measure- 
ments (+15 minutes for the 1956 data) and 
within ten miles of the location of the echo top. 
The heights were grouped into three precipita- 
tion categories: no hail (rain only), hail diameter 
less than 34 inch, and hail diameter equal to or 
greater than %4 inch. If an echo top measurement 
was associated with several reports of rain with- 
out hail and only one report of one-inch hail, it 
was put into the larger hail category. 
Echo top temperatures were read off the Al- 
bany, New York, radiosonde nearest in time to 
the echo height measurement. The tropopause 
height was also determined, where possible, se- 
lecting the height above the 300-mb level where 
the temperature lapse rate first became less than 
2°C/1000 ft. The distance by which the echo tops 
exceeded or fell short of the tropopause was re- 
corded. For echo tops penetrating the tropopause, 
an estimate was made of the negative energy re- 
quired for penetration by measuring the area 
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oe) 
0.3F 4 
2p x d NO HAIL, 450 OBSERVATIONS| 
— ——— HAIL SMALLER THAN 3/47 
92 OBSERVATIONS 
HAIL 3/4" AND LARGER 
OIF : 39 OBSERVATIONS 
Ove Lo 
sc H ¢ 
(oe 1 1 we Hie 
10 20 30 40 50 60 
THOUSANDS OF FEET 
Fic. 1—Cumulative frequency distribution of 
thunderstorm echo top heights 
- + NOHAIL, 450 OBSERVATIONS 
——— HAIL SMALLER THAN 3/4" , 
92 OBSERVATIONS 
HAIL 3/4” AND LARGER, 
39 OBSERVATIONS 
CUMULATIVE FREQUENCY 
TEMPERATURE IN DEGREES C 
Fic. 2—Cumulative frequency distribution of 
thunderstorm echo top temperatures 
bounded by the sounding, the dry adiabat rising 
from the tropopause (very nearly equivalent to 
the moist adiabat at stratospheric pressures), and 
the pressure surface at echo top. 
The results are shown in Figures 1 to 4, which 
show the cumulative frequency distributions of 
echo tops associated with each of the three 
precipitation categories with respect to height, 
temperature, penetration above (or below) the 
tropopause, and negative energy required for 
stratospheric penetration. Table 1 summarizes 
the upper quartile, median, and lower quartile 
values (in descending order) of these four param- 
eters for the three precipitation categories. 
The differences between the ‘all rain’ category 
and the larger hail category are quite marked, 
even considering the several sources of error. 
These errors include the uncertainty as to hail oc- 
currence and maximum hail size because of holes 
in the observing network almost certainly larger 
than significant variations in the character of 
thunderstorm precipitation. Thus, the proximity 
of the ‘all rain’ and smaller hail size curves on all 
four diagrams may be partly attributable to un- 
observed (or unreported) small hail that falls 
