Abstract:
Some extremely large oceanic trade-mind cumulonimbus clouds extending
upwards of 40,000 ft. into a region of strong winds and intense vertical
shear have been studied by means of time-lapse photography. A simultaneous
still picture of the clouds taken a known distance and direction away from
the motion pictures permits triangulation upon the clouds and calculation of
the vertical and horizontal motions of several of the individual towers. By
means of a nearby radiosonde observation, it is established that the air
forming the strongest of these towers must have risen from near cloud base
with little or no dilution of its buoyancy by mixing with the clear-air surroundings.
The model of Malkus and Scorer (1954) concerning the erosion of cumulus
towers is reviewed and tested upon these towers with satisfactory results.
A minimum horizontal cloud dimension is apparently required for the production
of undiluted towers. The horizontal motion of the clouds relative to
the air is also estimated from the model and tested by the observations and
the net upward transport of latent heat in water vapor is calculated approximately.
