THE STRUCTURE OF THE VELOCITY FIELD OF THE LOMONOSOV EQUATORIAL CURRENT BASED ON THE MEASUREMENTS IN SPRING 2014 AND AUTUMN 2015

Abstract

Two examples of measurements of oceanic equatorial currents in the Atlantic using an shipborne acoustic Doppler current profiler SADCP on meridional sections across the equator in spring 2014 at 23°W and autumn 2015 at 34°W are considered. The relevant data of some previous observations in this region are also used for comparison. The methods for studying the Lomonosov Current using ship profiling and moorings are discussed. According to the results of profiling with a two-minute averaging of the source data of the section of September 27, 2015, a structure of the two-dimensional section of the high-resolution velocity field is presented, which is characterized by small-scale fragmentary stratification, which was previously detected only from one-dimensional data of vertical soundings of velocity and other parameters of the ocean environment. Using the example of comparing this detailed section with the versions for other time averages (15 and 60 min) differences in the estimates of parameters of the velocity field due to the averaging are specified. Using the example of vertical profiles through the core of the Lomonosov Undercurrent (EUC) in the springs of 2002 and 2014 and winters of 2002 and 1971 at the locations close to 23°W, the stability of the annual cycle of fluctuations of the intensity of currents in the core and the position of the core in a multiyear aspect is illustrated. The agreement of our results with other previously published data is shown. The main parameters of the velocity field over the equatorial section on April 17, 2014 indicate a high probability of the outcropping of the easterly flow on the surface. Similar episodes of outcropping in 2002 within the PIRATA program together with corresponding intervals of changing the direction of the zonal component of wind speed derived from the Era Interim reanalysis from westward to eastward are demonstrated. A similar correlation with the wind is assumed to occur on April 17, 2014.