the earth and at 70 km from the coast the radon has only diffused up to 1500 meters.
Above 2000 meters the measured radon is that which comes from the ocean.
Theradon
concentration shows the presence of a mass of maritime air.
Ce
Combination of Two Air Masses of Different Origin
On October 6, 1966 there was a fog from the surface to 500 meters.
temperature gradient was slightly below adiabatic.
The
Figure 5 shows a rapid decrease
of radon with altitude.
At 1000 meters there was a temperature inversion.
meters was not of the same origin.
from Great Britain.
The air mass above 2000
It came from the north-west, that is to say
It contained more radon than that from the lower levels.
At
500 meters altitude the wind speed was 10 meters per second south, south~east,
while at 2000 meters the north, north-west wind was only 6 meters per second,
On October 5th we were in the path of a disturbance from October 4th (passage of
a cold front).
The sky was covered with cumulus between 800 and 2000 meters.
the surface the wind was weak and from the north, north-east.
the cloud base the wind was from the south, south-west.
At
At altitude above
Measured activity was
greater above the clouds than at their base (Figure 6).
D.
Case of a Maritime Air Mass
On December 6, 1966 we observed some exceptionaly weak activity(Figure 7).
A cold .front had passed during the day into the region where we were sampling.
The wii:d at all levels was from the north, north-west tut the air flow was from
the weste
The radon activity obtained at aititude showed that the air had stayed
long enough above the ocean so that it contained only small amounts.
Behind the
cold front we made a horizontal flight at 800 meters and took samples from the
coast to 150 km inland.
above the ocean.
The activity obtained was comparable to that measured
At 100 km the surface radon had only diffused up to 800 meters.
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