Climatological Atlas of Temperature and Salinity for the Northeast Asian Seas.

This study describes a monthly Atlas for the Northeast Asian Seas 2023 (ANAS23) with a 1/10° horizontal resolution and 73 vertical levels. For ANAS23, over 1.6 million hydrographic profiles were analyzed, utilizing a simple kriging interpolation technique, which considers data density and their covariance at each grid point, along with a profile stabilizing method to minimize damage to water-mass structures. Comparison of ANAS23 with previously published atlases, repeated sectional observations, and satellite-based geostrophic current fields reveals that the ANAS23 provides reliable descriptions of the spatial distribution of water masses, currents, thermohaline fronts, and mesoscale eddies while avoiding spike-shape noises, vertical instabilities, and artificial waters, particularly over large-topographic features. The ANAS23 could be utilized as a baseline to assess the dynamic state of climatological mean fields and their changes under evolving climates. The fact that uncertainty among atlases is still apparent, particularly in a region of scarce observations, calls for a collaborative international effort to collect qualified hydrographic observations for a better-performing regional atlas, thus improving predictive skills for future climate.