1999 Volume 77 Issue 6 Pages 1199-1220
Cumulus convection occurs over the Kanto plain during the afternoons of fair summer days. By investigating cloud amount data, it was revealed that the afternoon cloud amount on a given day, and that on the following day are dependent on each other. If the cloud amount is small on a given day, it tends to be greater on the following day, and vice versa. It can be concluded that fair weather does not tend to persist from day to day, when the Kanto plain is covered by the subtropical anticyclone and the weather conditions are stable.
The interdiurnal variation was then simulated in two-dimensional numerical experiments. Days with strong and weak convection appeared quasi-periodically, even though the complete diurnal boundary conditions were given corresponding to the sea and land breezes. By examining the results of the numerical experiments, it was shown that the interdiurnal variation resulted from differences in vertical profiles of potential temperature and water vapor mixing ratio in the lower troposphere. The ‘over-adjustment’ effect that the condition will become less favorable for cumulus convection on the following day as a result of strong convection, is essentially important for the interdiurnal variation.
Furthermore, the differences in the vertical profiles were compared with those from aerological data, in order to examine the above mentioned results of the interdiurnal variation. The differences simulated in the numerical experiments were qualitatively similar to those found in the aerological data, although the differences in potential temperature were not statistically significant.