FR.
5. In a moist atmosphere and with lorge bombs. the whole of the region marked X in Figure ‘3 -up to -and -including ‘the ‘stem, ‘should fill -with many
‘cumulus ‘clouds ‘soon after ‘the ‘vortex ‘ring -has.-begun ‘to -ascend,
6.
-The -cloud -will ‘ascend ‘until -if -regches -a ‘height -at ‘which ‘the -atmos-
pheric ‘stability ‘is ‘such as ‘to ‘oct as :a -“‘lid® through ‘which ‘the -yortex cing
.@s
ia: whole cannot -ascend; -in -general -this -level -will -be -at or slightly ‘above -the
‘tropopause.
On -reoching ‘this stable ‘level, the -vorfex -ring ‘and ‘its -attendont
‘cloud -will -expand ‘laterally -and -in :the -absence of other -sources of -energy. ‘the
‘circulation -will decelerate -and -be destroyed ‘eventually -by ‘turbulence.
‘Roughly
‘speaking, -if -may -be -estimated ‘that ‘the -destructive ‘effect of ‘mixing .-will -be
-greafesf ‘when ‘the ‘winds just -below -the tropopause ‘have ‘strong ‘horizontal -and -ver‘tical -shear.
‘7.
-The ‘vertical -velocities -will -reach -a :maximum -along -the -axial :stream-
cline -at -the ‘time ‘just -before ‘the -ring ‘reaches ‘its -maximum ‘height -and -at ‘the
point on -that -streamline ‘where -it -is :cut -by ‘the plane of :the ‘vortex -ring ‘(Figure
4),
-With -large -bombs ‘this :vertical -velocity ought to -reach -very -large ‘values.
Hf the -"!lid? -is -a -very -stoble -layer. -such -as the :lower ‘tropical «stratosphere,
‘the ‘central -fast moving ‘stem. -together -with -much -bomb -material, -may -be ‘carried
up ‘considerable -distances ‘into ‘the -stratosphere ‘os -a ‘narrow -* ‘plume’ -before
‘decelerating -fo -zero ‘vertical ‘velocity ‘(see ‘Figure -4).
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