R.Manasseh Fluid Dyn Papers
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The third circuit began with take-off from Camden at 1147. On the northern leg
(1209-1228), winds were north-westerly at 
. The amount of
cumulus had reduced since the last circuit; it was now 1-2 octas. About 10 km
from the coast, and at an altitude of about 400 m, the wind was found to be
south-easterly for 1-2 km, then north-easterly at up to the
coastline, turning northerly at 
immediately on crossing the
coast. The temperature at 400 m had been constant at 
over the inland
part of the metropolitan area; however, from the point where the wind turned
south-easterly, the temperature started to fall, reaching 
at the
coastline. Meanwhile the dewpoint temperature rose, indicating that a
higher-humidity air-mass was entered. Pollutant indicators were at negligible
levels.
The ocean leg (1228-1246) was flown at about 100 m altitude, starting from
Newport Beach extending further south than normal up to Garie Beach, because it
was thought that pollutant indicators might have been advected south by
conditions observed on the run. The winds were due easterly at about
off Newport Beach, changing to 
north-easterly by
the time Garie Beach was reached. Visually, there seemed to be much less smog
over the sea than on the previous circuit. A low peak in pollutant indicators
was found well south of Port Hacking. Temperature was roughly constant at
, rising to 
in the vicinity of Garie Beach.
A run was made out to sea in an easterly direction, maintaining a 100 m
altitude. Winds changed from east-north-easterly near the coast
to 
north-easterly 30 km from the coast, while the temperature fell
from to .
A run along the southern leg was made from 1311 to 1324, at an altitude of
about 180 m. Winds were north-easterly at 
up to a point about
15 km from the coast, where the winds because light, variable and
north-westerly. There was an abrupt drop in dewpoint temperature at this point,
indicating a transition to lower-humidity air. This is shown in
figure 4.
Low levels of pollutant indicators extended inland to the same point about
15 km from the coast. Immediately on reaching Warragamba Dam, a return
eastwards along the southern leg was made at about 450 m, extending 30 km out
to sea, to try to determine the vertical extent of the front. At this altitude
there was no clear change in wind velocity or temperature; winds were light and
variable although north-easterly winds of 
were present just at
the coast. Further offshore at 450 m winds became northerly at .
The flight ended with a landing at Sydney Airport at 1400.
Figure: The dry-bulb and dewpoint temperatures as the sea-breeze front was
crossed on the southern leg of the third circuit, at about 180 m altitude
R.Manasseh Fluid Dyn Papers
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