Long-term AVHRR SST change analysis in the Taiwan Strait using the rotated EOF method

Abstract

The Taiwan Strait (TS) connects the East China Sea (ECS) and South China Sea (SCS). Flow circulation in the TS exhibits complicated patterns during winter. The cold China Coastal Current (CCC) flows southward into the northwestern side of the strait as the warm Kuroshio Branch (KB) enters the strait along the southeastern side. In addition to the control that the northeasterly monsoon exerts over the CCC intrusion strength, the complex topography modifies the circulation. The winter temperature gradient in the TS is nearly horizontal. The sea surface temperature (SST) data reveal the main circulation features, including a distinct SST front in the middle of the strait. A rotated empirical orthogonal function (REOF) analysis is applied to the advanced very-high-resolution radiometer data to define four SST regions: the CCC and KB sources as well as the regions influenced by the Taiwan Banks and the Chang-Yun Rise. The Mann-Kendall trend detection method indicated that the SST in the TS (except in the KB region) abruptly increased during 1992-1994. The warming tendency in the KB region was slower compared with that of the other regions. The relationship between the El Niño-Southern Oscillation phase and SST variation in the TS exhibited spatial and decadal variations. The SST in the northern TS tended to be warmer (cooler) during El Niño (La Niña) years compared with normal years. However, the opposite relationship was found in the southern TS: SST cooling (warming) occurred during El Niño (La Niña) years and this phenomenon existed only after the SST warming regime shift (1992-1994).