The Results of Hydrometeorological Measurements by the Wavescan Buoy System on the Southwestern Shelf of the Peter the Great Bay in 2016

Abstract

For the first time, the long-term measurements of meteorological and oceanographic characteristics were measured using the anchored autonomous complex of the WaveScan buoy on the Southwestern shelf of the Peter the Great Bay (Japan Sea) from 21 April to 23 December 2016. The buoy anchor was set at 50 m depth. During 10 minutes of each hour, meteorological characteristics of the near surface layer of the atmosphere, sea water temperature at the horizon of 1.5 m, and vertical profiles of the current velocity vector from the near-surface layer to the near-bottom one were measured with resolution 4 m. During 20 minutes of each hour, the characteristics of waves on the sea surface were measured. In General, most of the meteorological characteristics measured on the buoy are in good agreement with the data of the NCEP-DOE AMIP-II, ERA-Interim and ERA5 reanalysis. The significant wave height for the whole frequency belt, mean wave period and mean spectral direction from the WaveScan Buoy measurements have the best statistical relationship, confidence level is 99%, with the correspondent significant height of the waves, mean wave period and mean spectral wave direction from reanalysis ERA5. The features of variability of vertical profiles of the current velocity vector on the synoptic and seasonal time scales that depend on wind speed and vertical stratification of density are determined. In the warm season the a significant left turn of the vector of the measured current velocity with depth is observed in the seasonal pycnocline below the surface layer of friction. At wind speed, not exceeding 5 m/s, the angle of the current velocity vector left turn reaches 170° in the bottom layer, where countercurrent is formed. During the passage of the Lionrock tropical cyclone, when and the daily mean wind velocity increase to 9 m/s, the angle of left turn of the current velocity vector in the pycnocline decreases to 20°. In the cold season a classic right turn of the current velocity vector is observed in the upper boundary layer, and the vertically average velocity vector within the 50 m layer, as well as the total drift flow in the Ekman friction layer, deviate 90° to the right from the surface wind velocity vector. The left turn of the current velocity vector at the buoy installation point was not observed in the cold season.