The Longitudinal Structure of Interannual Variability Observed in Sea Surface Temperature of the Equatorial Oceans

[摘要] The longitudinal structure of interannual variability (IAV) of sea surface temperature (SST) is examined diagnostically for the period 1949-97 (49 years) in the entire equatorial oceans (5°N-5°S). In the centraleastern Pacific to the east of 170°E, the mean SST is lower than 29°C, the variance of SST IAV is large, and the air-sea coupling on the IAV timescale is strong. There further appear two variance maxima of the SST IAV around 160°W and 90-100°W. The variability in the 38-47-month band (LF1) is dominant at 90-100°W, while both LF1 and the 51-68-month variability (LF2) are large at 160°W. The contribution of 18-32-month variability (QB) is also large but not as that of LF1 and LF2. The detailed propagation direction is changed according to the periodicity in this region, i. e., eastward in the LF2, but is westward in the QB and LF1. Strong air-sea coupling is identified in all LF1, LF2, and QB. In the Indian Ocean-western Pacific sector to the west of 170°E, the mean SST is higher than 28°C, the variance of SST JAY is small, and the air-sea coupling is weak on the IAV timescale. The SST IAVs in the dominant QB, LF1, and LF2 exhibit a common phase structure in the Indian Ocean-Pacific sector. These SST IAVs are in phase in the central-eastern Pacific, but are out of phase in the western Pacific with a node around 170°E indicating a standing seesaw-like oscillation in the Pacific. In the Indian Ocean, the SST IAVs lag from a few to several months behind those in the central-eastern Pacific.In the Atlantic sector, the longitudinal change in the mean and variance fields are similar to that appearing in the Indian Ocean-Pacific sector. The IAV of SST tends to lag behind that in the centraleastern Pacific in general, but does not show the other common phase structure in the QB, LF1, and LF2 in detail. The air-sea coupling is weak on the IAV timescale in the equatorial Atlantic.

[学科分类] 大气科学