Abstract
July 14, 1969 was selected from BOMEX Period IV as the day of detailed analysis of cloud velocity fields over the northern tropical Atlantic Ocean. A total of 375 low-cloud velocities were obtained between ITCZ and 34N and 70 velocities between ITCZ and the equator. These velocities are found to be very useful in understanding circulation patterns over a vast region of water where little synoptic data is available. Over 170 high-cloud velocities were computed mostly in the area of cloud clusters. It was found that a field of high-cloud divergence existed over practically each of large cloud clusters in the ITCZ and an easterly wave appearing on this day. Motion of dust clouds from Sahara was also computed by using an accelerated movie technique. It is concluded that ATS III picture sequences can be analyzed independently from conventional synoptic and/or network data so that the computed velocities of clouds, dust, and propagating waves can be used as supplementary data to past and future tropical experiments.
