Variation of the summer low SST area in the southwestern coast of Korea

Abstract

Variation of the low sea surface temperature (LSST) area in the southwestern coast of was analyzed using the daily satellite-observed sea surface temperature data in 2005. The harmonic fitting method was used to separate the long-term variation (= annual + semi-annual components) from the raw data at each grid point, and the residual was estimated by subtracting the longterm component. Investigating the amplitude and phase of tidal components such as M_m and M_f made possible to check the tidal variability of LSST especially in August, and the area of LSST was estimated by comparing the long-term value and linear correlation with lowest SST area. SST was decreased during the spring tide and increased during the neap tide, and the maximum SST difference between the spring and neap was about 5 °C, and horizontal gradient was 0.05–0.1 °C/km in the area. When the LSST area in August was defined by using two conditions: lower SST than the long-term variation and high correlation coefficient with the lowest temperature area at 34.5°N, 125.65°E, it varied with tidal period showing peaks during the spring tide. The area also showed inphase for the M_m and M_f components with 0.9–1.5 °C of amplitude, and especially the phase distribution of Mf showed the elongatedcircular around the lowest temperature area, indicating that the tidal mixing could be a major factor of this phenomenon. The maximum LSST area were 2.69×10⁴, 8.71×10³, and 2.62×10³ km² for the correlation coefficients 0.85, 0.90 and 0.95, respectively.