18 TOR BERGERON 
then, that they originated from showers that 
became arranged parallel to the direction of the 
general flow, merging into solid rain bands of 
spiral shape and eventually mto one ring-shaped 
rain-area as they came under the influence of the 
general updraft. I think that detailed precipita- 
tion studies of tropical hurricanes might form a 
useful complement to the radar scanning of 
them, since, after all, the radar does not render 
the rain intensity as truly as the gages do. 
Moreover, the radar patterns do not show the 
total extent of clouds, but only the patches with 
efficient release of precipitation. Thus, they per- 
mit no estimate of the amount of latent heat 
released. In other words, the release of latent 
heat need not be so discontinuous as 1t may seem 
from the radar pictures. 
The problem of orographic precipitation is old 
General formula: 
w I Iw 
Mee, Aalh_ jotm,imy, | Uy Fulks’ solution: 
Qos Os 
Qor 07 
0.6 
05 
and much treated. Therefore, I shall here only 
enter on a most remarkable case of exceedingly 
abundant orographie precipitation that occurred 
over southern Scandinavia in the last week of 
March 1927, when a front lay quasistationary 
from the Black Sea over Poland and Denmark 
to Iceland, and there was frontal precipitation 
all over southern Scandinavia together with 
southeasterly winds. Figure 11 gives a close-up 
of the weather situation over southern Norway 
and the immense amount of precipitation, 200 
mm (8 in.) that fell in exactly three days on the 
coast. That could not be ordinary orographic 
precipitation. In this case the static stability of 
the general southeasterly current made part of 
it bend outside the mountains and meet the 
direct southeasterly branch as a northeasterly 
current. Thereby an orographically conditioned 
Z 
5) 2 w'A*g@ = 6z 
al 
= 780 ae - 2166 ‘, 
T 
6T 
oS ie 
horizontal area 
max. spec. humidity 
air density 
partial pressure 
of water vapour 
= rate of ascent 
Teton 
aes (0) 
Warm cloud 
Supercooled cloud, 
not released 
released 
THI 
Supercooled cloud, 
O° ST 36°C 
6 7km 
Fic. 12—Vertical distribution of maximum condensation intensity Zw in an upslide cloud system 
