Wind Pressure Fields Research Articles

On currents, internal and inertial waves in a stratified ocean due to variable winds. Part 2

The response of a continuously stratified viscous ocean to a variable wind and air pressure field has been studied during recent years by means of analytical methods. This requires the assumption of consntant eddy viscosity and exponential stratification. In shallow water constant eddy viscosity leads to irrealistically thick boundary layers compared to the water depth and, theorefore, eliminates internal waves. In the first part of a two-part study a theoretical model has been developed for arbitrary density stratification and eddy viscosity. The results of the integration are dealt with in this second part 2.

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. DOI: 10.1111/j.2153-3490.1976.tb00699.x

Magnetic conjugacy at very high latitude; shepherd bay-scott base relationship

Magnetic variations occurring at very high latitudes have been studied to determine if they are similar at conjugate points, how the conjugacy or non-conjugacy changes during the day and season, and how this may be related to the sources of the disturbances and the field lines in the magnetosphere. Data from the conjugate pair Scott Base, Antarctica and Shepherd Bay, Canada were used in this study. Two basic types of magnetic activity must be considered, occurring at about the times the midpoint of the field line linking the pair is at the noon and midnight meridian. The field line midnight activity seems to result from auroral zone electrojets, and its conjugacy or non-conjugacy relates to the relative locations of the stations to the respective auroral zones. Field line noon activity is evident even on very quiet K p , days and usually amounts to several hundred gammas irregular variations. It seems likely that this “dayside agitation” relates closely to the neutral point field lines, or on the magnetosphere surface under the solar wind may transmit particle fluxes or H− M waves down the field lines on the day side. Both the dayside and night-time types of activity show poor correlation at the conjugate points. Intervals of essentially one-to-one correlation can be found at almost any time during various days however. On the average the best correlation corresponds to the interval following the auroral zone type activity but preceding the dayside agitation. This also corresponds to the average quietest time of the day. These variations may be of global character, reflecting changes in solar wind pressure or interplanetary magnetic fields.