Vertical gradient correction for the oceanographic Atlas of the East Asian Seas

Abstract

AbstractRegional climatology around the East Asian Seas has been developed by an international collaboration between the National Oceanic Data Center and the Korea Oceanic Data Center. It provides reliable information on temperature and salinity climatological fields with high resolution (0.1° × 0.1° by 137 levels). However, there is a problem around near‐bottom areas where topographic change is steep and observations are not available near the bottom. This study resolves this problem using a vertical gradient correction method when the profile is statically unstable. The stability is determined based on the Brunt‐Väisälä frequency with individual temperature and salinity profiles. Topographic‐following mapping technique employing the potential vorticity constraint term is used to construct a vertical gradient database for the temperature and salinity at every grid point. The results show that the correction is effective for eliminating large erroneous vertical gradients around near‐bottom areas. In addition, we show the importance of the optimal length scale to construct a precise vertical gradient database in a particular area such as the northern shelf of Taiwan. We expect that our revised high‐resolution climatological mean fields will serve as important data for relevant studies around the East Asian Seas.