Some results of the surface wind and atmospheric pressure fields analysis near the Equator



Based on meteorological observations from five USSR research ships during Expedition TROPEX-72 in the Atlantic Ocean for the period from June to August 1972, the relationship between surface winds and pressure gradients near the Equator is analysed. For the narrow Equatorial zone (0–2.5° N) the nearly complete independence of the surface wind speed (rather strong 7–8 m/sec) and direction from the local pressure gradients was found and on this basis the conclusion is drawn concerning the important role of the air stream inertia in this zone. However, the estimates of different terms in the equation of motion for the near-Equatorial latitudes showed that, as in the middle latitudes, the inertia terms of the mean motion are here one order of magnitude smaller than the terms of pressure gradient. Having this in mind we believe that the only proposition which could be made concerns the important role of the inertia associated with turbulent rather than average motion in the dynamics of the Equatorial atmosphere. It is shown that the inertia of the air stream near the Equator can account for the asymmetry of the vorticity field around the axis of the Equatorial trough (cyclonic relative vorticity north of the trough axis and the anticyclonic one south of the axis in Northern Hemisphere). It is shown that the wind deflection angles become normal for the usual geostrophic relation over the sea only north of 11–13° N.