Kinematic and thermal structures of two surges of flow in the Northern Mozambique Channel Area

Two atmospheric surges near the northern Mozambique Channel were explored by NCAR's Electra aircraft on 17 June 1977 and 3 July 1977 during MONSOON–77 field experiment. The surges were probed from Nairobi eastwards to the coast and then south from 1°S to 8°S along 41°E. Offshore the former day was characterized by deep south‐south‐easterlies and south‐easterlies, squalls, and rain and the latter day by shallow south‐south‐easterlies overlain by south‐westerlies and fair weather cumulus. Vertical structures of u , v , T and q for both days are discussed. Early on the disturbed day southerlies reached their maximum over land at 880 mb on a cross‐section approximately along 2°S. By noon diurnal heating reduced the overland winds, resulting in an apparent ocean‐ward shift of the jet axis. On the undisturbed day the southerly maximum was over the ocean near the coast. On both days two southerly maxima were found on longitudinal coross‐sections along 41°E: an elevated and stronger maximum near the equator; a depressed and weaker one near 8°S. On the disturbed day the equatorial maximum was located in the south‐south‐easterlies and on the undisturbed day was sandwiched between south‐south‐easterlies in the low levels and south‐south‐westerlies at 770 mb. The southern maximum was from south‐south‐east on both days. During these two periods meridional mass fluxes from two stations, Port Elizabeth and Dar‐es‐Salaam, were computed. They showed that the latter station lags the former by as much as four days; however, its meridional mass flux is double the former.