Another candidate is acceleration by thermal tides, which are excited in the cloud layer by periodic solar heating and which propagate vertically to induce momentum exchange between atmospheric layers (Fels and Lindzen, 1974; Newman and Leovy, 1992; Takagi and Matsuda, 2005, 2007).
Thermal tides will be excited in the cloud layer by periodic solar heating and propagate both upward and downward (Fels and Lindzen, 1974; Newman and Leovy, 1992).
This implies that the amount of cloud that extends horizontally at the top of boundary layer is small in the one-moment scheme, which is because of the liquid water removed from the cloud layer earlier by precipitation.
Durant et al. (2009) proposed that observations of weakly turbulent mammatus lobes at the base of the volcanic cloud over a wide area (including Ephrata, WA; Moses Lake, WA; and Vantage, WA) implicated bulk settling of the cloud layer driven by ice crystal formation and sublimation at the cloud base.
The Vega balloons were dropped into the cloud layer of Venus by the Soviet Union and France in 1985 and observed meso-scale cloud processes and horizontal advection over 46 hours (Sagdeev et al, 1986).
In this observation mode, a particular point on the cloud layer is continuously monitored by using the UVI, IR1, IR2, and LIR from distances shorter than ~50,000 km for the purpose of observing the temporal development of mesoscale processes and also for stereo-viewing of the cloud tops.
The images taken by LIR will visualize convective cells and various types of waves within the cloud layer.
On the nightside of Venus, VIRTIS data revealed cloud contrasts in thermal emission from the cloud layer (Peralta et al. 2017) and also revealed cloud layer opacity variations above the lower clouds which are back-illuminated by emitted radiation from the warmer atmosphere below the cloud layer and the surface (Hueso et al. 2012).
The thickening of the cloud layer, the splitting of a cloud layer, the changing height of a cloud layer are all ascribed to the presence of waves with rather long wavelengths in the cloud layer.
"The cloud layer is only 1,500 feet two minutes and we'll pop up above.
