PROBLEMS AND METHODS OF RAINFALL INVESTIGATION 19 
convergence was set up at the SE coast of Nor- 
way, with a mighty updraft just at the coast, 
and consequently a very intense condensation in- 
side the orographic cloud system. 
Figure 12 shows the amount of precipitation 
to expect from an upslide cloud system according 
to Funks’ formula, assuming +10°C at a cloud 
base lying very near the zero level. Such dia- 
grams give a measure of the maximum condensa- 
tion intensity 7 under the assumption made as 
to the vertical motion shown by the curves w 
in the figures. The maximum condensation in the 
cloud mechanisms in question in each unit layer 
(100 m thick) is obtained by the Jw curve. 
Integrating the area enclosed by this curve and 
the zero line gives the maximum amount of pre- 
cipitation available under the asumption that 
there was no entrainment, and that the precipi- 
tation release was 100%, that is, total and im- 
mediate. Naturally, in reality one gets much less, 
generally only about 50 or 60% of the theoretic 
maximum, which in this case is 0.9 mm/h. Since 
the temperature at the cloud base in this case 
was about O°C (instead of +10°C) and the 
distance to the front line at the Earth’s surface 
100-200 km, one can expect at most 30% of the 
maximum value or not more than about 20 mm 
precipitation on the Norwegian coast from the 
upshde surface during those three days. So we 
have to explain the remaining 180 mm by the 
above-mentioned orographically conditioned 
mechanism. A cross section SE-NW over Skage- 
rak and the southern Norwegian mountains 
(Fig. 13) shows the frontal upslide surface with 
the upslide cloud system and snow falling from 
it. Within the cold air lies the orographically 
conditioned, local mechanism that causes a much 
stronger updraft and a much more intense 
condensation: the feeder cloud. The water con- 
densed is brought down promptly by snow fall- 
ing through this cloud from the overlying re- 
leaser cloud. 
Ayn 
57 = > 
—— 
zal SOT 
So 
5 
* 
Inversion 
~, 
1+-SssTIDSTRI/S 
RAINS 
Orographic Precipitation in Detail 
tes. 
LEGEND 
Floating ice-needles 
Falling precipitation 
Floating cloud droplets 
mre Ice mucleus level 
i le Falling snow 
919! DE 
<——<——— Flow of warm air 
wr uJ BES Hopes, 
Front surface 
> 
Fic. 13—Schematic vertical cross section of frontal and orographic precipitation mechanisms in 
Southern Norway, March 24-27, 1927 
