Monthly Variation of Sea-Air Temperature Differences in the Korean Coast

Abstract

Monthly variations of sensible heat, latent heat and momentum fluxes and the modi- fication of sea temperature to air temperature were examined at four coastal sta- tions—Sokcho, Kangnung, Ulsan and Chungmu in the path of the East Korea Warm Current from the year of 1981 to 1990, which was one of main migration routes of Japanese common squid. The difference between monthly averaged sea surface and air temperatures at the 10 m height above the sea surface mainly became negative values from April through August, while they had positive ones from September through March. Monthly variability of the temperature differences is significant in both summer and winter, while it is generally small in spring and fall. Negative val- ues of sensible heat fluxes, which indicated a heat gain by the sea through heat con- duction across the air-sea interface were found at the four coastal stations from April to August. Minimum values of sensible heat fluxes at Sokcho, Kangnung and Chungmu were in June, except for Ulsan in August. To the contrary, positive sensible heat flux implying a heat loss from sea toward atmosphere occurred from October to February with a maximum in December. Latent heat fluxes due to condensation of moist air over sea surface had small magnitudes from April to August and those due to evapo- ration of water particles from the sea surface into the lower atmosphere had rela- tively large magnitudes from October to March. Minimum values of latent heat fluxes also occurred in June except for August in Ulsan. Momentum flux was small from June to August under weak wind in summer, but it was large from December to Feb- ruary under strong wind in winter. Regression equations between sea surface tem- perature and air temperature at the 10 m height above the sea surface had very high correlation coefficients from 0.92~0.98, except for 0.78~0.84 of Ulsan, which was par- tially affected by upwelling of cool water from the bottom into the sea surface. Simi- lar to the sea surface, correlation coefficients were over 0.83~0.97 except for 0.70~0.79 for Ulsan at the 10 m depth of sea and were over 0.70~0.95 except for 0.59~0.82 for Ulsan at the 20 m depth.