Xie, S., 1994: On preferred zonal scale of wave-CISK with conditional
heating. Journal of the Meteorological Society of Japan, 72(1), 19-30.
Abstract: Wave-CISK (conditional instability of a second kind)
with conditional heating on a rotating sphere is investigated using a global
spectral model. With certain initial conditions, an eastward-propagating
wavenumber-one mode with a single ascending region is obtained. With more
general initial conditions, however, more than one convection events, of
nearly equal strength and separated at nearly equal intervals, coexist
and interact very little with each other. This happens when the radius
for a convection event to affect other such events, which is inversely
proportional to the growth rate, is much smaller than the circumference
of the earth. In addition to the eastward propagating modes, a westward-propagating
mode is also found, whose flow field is dominated by gravity wave response
to the cumulus heating.
The above results indicate that the wave-CISK with conditional heating
does not always select the eastward-propagating wavenumber-one mode. An
alternative mechanism that leads to the selectivity of the wavenumber-one
mode is suggested.