In the same manner as with page2.html, and supplementary to it, this study of winter monsoon clouds follows earlier collaboration
with Joanne and Robert Simpson at the University of Virginia. This page shows various interesting cloud formations,
notably "slender" cumulus humilis (Warner 1982). Slides by Joanne and Robert Simpson together with Warner's black and white film have been used here.
A weak vortex disturbance occurred off Borneo on 16 and 17 December.
(back to main page).
After much flight near stratus layers and above shallow cumulus, an overcast was briefly encountered below flight level:
1118. about 10.1 N, 111.4 E, altitude 6.8 km on 320 azimuth. (back)
At the northern extremity of the aircraft track conditions remained undisturbed with many layers of cloud:
1157. 11.9 N, 113.8 E, altitude 7.4 km on 060 (left) and 240 (right) azimuth.(back)
1209. 10.8 N, 114.4 E, alitude 7.4 km on 060 azimuth.
Lines of small cumulus aligned roughly N-S, mostly confined below the level of stratus. (back)
1216. 10.4 N, 114.7 E, altitude 7.4 km on 030 azimuth.
Cumulus confined below the level of stratus, and arcs of stratiform cloud oriented towards the east. (back)
1218. 10.3 N, 114.8 E, altitude 7.4 km looking N.
Looking back on arc seen above. (back)
1219. 10.2 N, 114.8 E, altitude 7.4 km on 240 azimuth.
Cumulus humilis at quite large number density were sheared towards azimuth 330, indicating relative winds below this level
from the opposite direction.
The coastline of an atoll may be seen in the middle of Joanne's view. (back)
1225. 9.7 N, 115.1 E, altitude 7.4 km on 030 azimuth.
Slender small cumulus sheared towards the north. From the slenderness, unstable stratification and an absence of subsidence
at the level of the clouds is inferred. Note (in stereo) the presence of stratus between the top of the largest cumulus and flight level.
(back)
1229. 9.4 N, 115.3 E, altitude 7.4 km on 060 azimuth.
Note the evident feebleness and intermittency of cumulus updrafts, and the arrest of ascent at a stable layer where the cloud is spread out.
(back)
1230. 9.3 N, 115.3 E, altitude 7.4 km on 140 azimuth.
By RHS from the cockpit. The anvil was towards roughly azimuth 250. Note the absence of marked wind shear through flight level:
local cumulus towers were nearly vertical. (back)
1235.05. 8.9 N, 115.55 E, altitude 7.4 km on 240 azimuth.
The top of a cumulus evaporating at flight level. The last remnant of updraft may be perceived, with fallout below.
Cumulus were rising gently through unstable stratification. (back)
1235.09. 8.9 N, 115.55 E, on 240 azimuth.
The same view taken a few seconds later. The interval between right and left eye views was minimal, about a second.
1239. 8.65 N, 115.7 E, altitude 7.4 km on 040 azimuth.
A small patch of slender cumulus humilis, denoting locally an absence of subsidence accompanying unstable stratification.
The humilis were sheared towards about azimuth 050, indicating a low level wind maximum from 050.
(back)
1245. 8.3 N, 116 E, altitude 7.4 km on 045 azimuth.
Photos by Joanne Simpson. Linear features of slender cumulus fractus and humilis. There was an absence of strong winds near the surface.
Note the areas with a total absence of cumulus. The tall congestus was very roughly 70 km distant.
(back)
1300. 8 N, 115.2 E, altitude 7.8 km on 180 azimuth. Left half of pan by RHS.
1300. 8 N, 115.2 E, on 270 azimuth. Right half of pan by RHS. Strong ascent.
(back)
1301. 8 N, 115.2 E, altitude 7.8 km on 160 azimuth.
1310. 8 N, 114.3 E, altitude 7.8 km on 210 azimuth.
Strong ascent.
(back)
1318. 7.7 N, 113.6 E, altitude 7.8 km on 140 azimuth.
Quite a thick anvil at altitudes through flight level. (back)
Much of the return part of the flight was in cloud, with no photos taken.
1455. 3.5 N, 106 E, altitude 7.8 km .
Pan from cockpit by RHS. On azimuth 165 (150 left and 180 right).
Streets are of orientation 230 - 050
and suggest relatively strong winds from 050 at low levels.
(back)
1504. 3.4 N, 105.4 E, altitude 7.8 km on 040 azimuth.
Similar to the view following, a difficult partial cross-eye stereo-pair between a color slide by RHS and black and white film by Warner.
Taken at the time of a loop for tests of wind measurement. (back)
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1506. 3.5 N, 105.6 E, altitude 7.8 km on 030 azimuth.
Near the surface, streets were aligned along 320-140 degrees, probably close to the wind orientation.
Rows of slender humilis were aligned along 290-110 degrees. The tops of the cumulus humilis were sheared towards 330 degrees,
implying relative flow from this direction.
Several instances have been shown here of slender cumulus humilis. The appearance stems from shallowness of roots in the sub-cloud layer. It appears to accompany both unstable stratification and an absence of subsidence. Systematic search for appearances of slender cumulus humilis has shown no particular circumstances of occurrence. They occurred occasionally on nearly every mission in WMONEX. The phenomenon appears to reflect the variety of mechanisms by which activity in the boundary layer allows responses to forcings on larger scales. (back to main page)