OPERATION AND RESULTS OF ‘PROJECT PLUVIUS’ 
17°30'E_Gr ITs 
2 
Yi AK 4 G 3 
hs Cog 
ROT} 
1730’ E Gr 
Rainfall mm 
ASQ Woodland 
S7T7™ Isohyetal of 5 mm s 
== Shore line 
Lu 
One night: 14.X.18z- 15.X.06z, 1953. 
oat Town of Uppsala i 
Station reporting 51 mm rain 
Ground >40m ab s-l 
Min. Minimum of rainfall 
Fre. 2—Orographie rainfall maxima and minima around Uppsala, Sweden, during one night within a 
stationary and continuous frontal upslide rain area, as shown by a meso-scale network of Pluvius gages; 
the arrows show the wind direction 
think that one could use the data from the 
Thunderstorm Project in the United States for 
the same purpose. However, they had only be- 
tween 50 and 60 stations, and their areas pre- 
sented no marked orographic features. As early 
as 1953 we had 150 stations, and later, in other 
parts of Sweden, we had up to 800 stations. 
So, we could cover a much greater area, having 
an interesting orography, whereas the Thunder- 
storm Project did not have these requirements. 
On the other hand, evidently, the Thunderstorm 
Project and other similar projects had a much 
better instrumentation at each individual sta- 
tion. We could not afford that. The official meas- 
uring instrument of the Swedish Weather Bu- 
reau costs twenty times as much as the ‘Pluvius,’ 
and we had the choice between 1000 of this type 
and 50 of the former type. We had to choose the 
‘Pluvius.’ Then also the data from the different 
American and other projects were generally not 
accessible to us, as you will understand. 
In Figure 2 one rain maximum lies to the lee 
of Uppsala, and one might think of a precipita- 
tion release caused by certain nuclei produced in 
this town, or by the convection released through 
the heating effects of Uppsala; all sorts of other 
explanations may pass your mind. One might 
also think that this was just a chance distribu- 
