WATER VAPOUR IN THE UPPER AIR 
fication of the water content is observed, the tempera- 
ture variations from a smooth temperature-height curve 
are only about 140 or !%0 of the variations shown in 
the frost-point—height curve. As in the horizontal plane, 
low frost points tend to be associated with relatively 
high air temperatures. 
It is the writers’ experience that the atmosphere is 
extremely variable in this respect; the structure is 
sometimes relatively simple but sometimes very com- 
plex. Figure 10, for July 30, 1947, shows measurements 
on both ascent and descent through a dry layer. As 
might be expected, the height and detailed structures 
change between ascent and descent, there being a dif- 
ference in both the time and place. 
FUTURE WORK 
Only data collected by the Meteorological Research 
Flight and by Barrett and collaborators are at present 
available, and only a very few ascents with accurate 
humidity measurements have yet been published. 
Experience in England has shown that almost every 
ascent is of great interest, and features are frequently 
observed which are difficult to explain. There is an ur- 
gent need for more observations in every part of the 
world in all types of weather and particularly on a 
synoptic basis, mainly to permit a systematic study of 
the widespread and fundamental phenomena of subsi- 
dence. The structure of anticyclones, both warm anti- 
cyclones and also winter continental anticyclones such 
as the Siberian High, will prove of interest. The higher 
tropopauses which occur in warm anticyclones have not 
yet been investigated in England because they are be- 
yond the ceiling of the Mosquito aircraft used. The 
scope for the useful collection of observational data is 
believed to be world wide. Meteorologists will also have 
to learn to use and appreciate the data. 
On the instrumental side the eye instrument is very 
satisfactory as a reliable instrument which will get re- 
sults, but the observational skill required will inevita- 
bly restrict its use. A fully automatic hygrometer for 
widespread use is urgently needed, but the develop- 
ment of such an instrument is a difficult problem and 
will not easily be solved. It is also hoped that alterna- 
tive methods, such as the spectroscopic method, or the 
method of Simon and Peckover, will be pursued. 
We are greatly indebted to the Director of the 
British Meteorological Office for permission to repro- 
duce unpublished data obtained by the Meteorological 
Research Flight of the Office. Figures 1 and 2 are re- 
produced from the Proceedings of the Royal Society by 
permission of the Council. Figure 3 is reproduced by 
319 
permission of the Physical Society, London. The synop- 
tic charts are reproduced from the appropriate British 
Daily Weather Reports by permission of the Controller 
of His Britannic Majesty’s Stationery Office and the 
Director of the Meteorological Office. British Crown 
Copyright is reserved. 
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