154 
17°30' E Gr 
TOR BERGERON 
ea 
SO 
peso 
Ra 
7 
, 
Oey 
1730’ E Gr. 
Rainfall mm. 
rs } Woodland 
—=—> Shore line 
157/77) \sohyetal of 15mm (es 
One night: 
AY Town of Uppsala 
1s! Station reporting 15.1 mm rain 
” « 5 
15.X.18z - 16 X.06z, 1953. 
Ground >40m ab. s.-l. 
mn. 
(tenths unknown) m 
} Minimum of rainfall 
——— 
Fic. 3—Orographic rainfall maxima and minima during the following night under the same general 
conditions as in Fig. 2 
tion; but the next night, skipping the interven- 
ing 12 day hours, we got much greater amounts, 
but practically the same distribution (Fig. 3) 
with the same stationary rain, and almost the 
same wind direction. The wind had shifted a 
little more to NNBE, but notice that in both eases 
the proportion between maximum and minimum 
was three to one. (Here it is about 20 to 7, on 
the previous map it was 7 to 242.) During the 
intervening and following day-time periods there 
was a similar pattern, but not so regular. This 
may be explained by the fact that in daytime, 
even at this high latitude and so late in the year, 
there will be some convective effects. Some heat 
will pass through the cloud, heat the ground, 
and disturb the cloud sheet. 
As seen from Figures 2 and 3, in this case the 
highest elevation of the country from the sur- 
rounding plain is about 50 m; one cannot ex- 
pect an increase of the rain to the double or the 
three-fold only by a lifting of 50 m. With a high 
condensation level that would hardly give any 
precipitation at all. True enough, if the low lay- 
ers are moist, clouds may form even over small 
hills. But if higher layers are cloudless, these low 
cloud caps will be colloidally stable and sym- 
metric, giving practically no precipitation, since 
there is no upper releaser cloud. Moreover, 
