The horizontal movement of cumulus humilis clouds near Sapporo was measured by the stereophotogrammetric method in the summer seasons of the years 1969 to 1971 in Sapporo. The direction and speed of individual cloud movements were presented on charts. The environmental meteorological conditions were obtained from the Sapporo rawinsonde soundings. By comparing the analytical results of clouds with the environmental meteorological conditions, the following results were obtained. The direction of horizontal movement of the higher cumulus humilis clouds was nearly the same as that of prevailing wind direction at the cloud level (exactly speaking, near cloud base level), however, the direction of the lower clouds was not in agreement with the wind direction. The critical ground height for the agreement of cloud motion direction with wind direction was found to be about 700 meters. The speed of horizontal movement of cumulus humilis clouds was generally less than prevailing wind speed at the level of cloud base. It was also found that the speed of larger clouds was slower than that of the smaller clouds when their heights were the same. The general tendency was that the lower the clouds, the lower the motion speeds, and the greater the vertical wind shear, the lower the cloud speed. The slowness of cloud speed was qualitatively explained by considering the upward transportation of low horizontal momentum in thermal convections under a condition of the positive vertical wind shear.

No abstract

The time change in position and size of cumulus clouds formed periodically in the lee of an island was measured by the stereophotogrammetric method. It was found that the observed cloud interval was different from the cloud interval calculated with the occurrence period of the individual cloud. The mechanism for the difference was discussed.

The meridional wind compnents and the vertical p-velocities over the east coast of Peninsular Malaysia and Singapore were computed for the period of the heavy rain spells from 13th to 25th December 1982. The relationship between the heavy rain spells and the Hadley cell was investigated.The following significant features are noted : (1) The formation of the heavy rain spells over the east coast of Peninsular Malaysia and Singapore are mainly caused by strong upward motions of moist air in the southern branch of the Hadley cell. (2) The maximum upward velocities in mid-troposphere are caused by the combination of strong low-level convergence and the initial appearance of the equatorial cell in the southern branch of the Hadley cell.

A tropical cumulonimbus cloud over the Malayan Peninsula was studied by means of the stereophotogrammetry.After three dimensional analysis of the cloud, the following results were obtained : 1) Intermittent updrafts in Cb clouds developed into a petal like form and a hole was observed at the top.2) An anticyclonical sucking action by the cumulonimbus cloud was observed at an altitude of 4 to 5 km, that is, just above the level of low cumulus cloud.