Quantifying Coastal Upwelling Index in the Southeastern Coast of Korea

Many studies have focused on detecting coastal upwelling off the southeastern coast of Korea. Frequent occurrences of coastal upwelling are attributed to the persistent southwesterly (alongshore) wind blowing in the boreal summer season by the East Asian summer monsoon, reducing the surface water temperature by more than 5^oC. Not just coastal upwelling cause variations in hydrodynamics, but it also gives rise to the primary production augmentation by phytoplankton blooms due to the supply of nutrients and fishery industry damage owing to sudden changes in water temperature. Accordingly, optimal coastal upwelling detection plays a crucial role in helping the augmentation of primary production and preventing industrial damage. Even though upwelling indices for detection are suggested, it would be inadequate to represent coastal upwelling compared with in-situ water temperature off the southeastern coast of Korea. Thus, we suggest upwelling-driven cold-water detection based on time-series observation, especially for real-time applications. By removing seasonal trends, we can define that an anomaly in sea surface temperature has occurred when the water temperature is out of natural variability (> 1σ). Furthermore, the suitability of the cold-water index was evaluated through an analysis between the index and the prerequisite when upwelling occurred, such as alongshore wind stress, wind duration, and vertical stratification.