Satellite Observation on the Exceptional Intrusion of Cold Water in the Taiwan Strait

Yi Chang,Kuo-Tien Lee,Ming-An Lee,Kuo-Wei Lan

doi:10.3319/tao.2008.08.07.01(oc)

Abstract

We used satellite-derived sea surface temperature (SST) data for the winters of 1996-2008 to examine the exceptional intrusion of China Coastal Cur rent into the Tai wan Strait. The long term observation reveals that, in 1999 and 2000, the strong wind (＞ 6 ms^(-1)) lasted for 12 and 16 days with a drop of 5.35 and 5.5℃ in SST, respectively. The satellite data also showed that the China Coastal Current intruded from the north of the Chang-Yuen Ridge into the waters surrounding the Peng-Hu Is lands, with wind speeds of more than 6.7 ms^(-1) lasted for 30 days during the same period. The exceptional intrusion resulted in the minimum SST of 12.6℃ on 16 February 2008, 7.8℃ lower than the 12-year aver age of February (20.4℃). The higher SST (＞18℃) appeared after 21 February 2008 indicating the north ward withdrawal of the cold water. During the period of 15-21 February 2008, the China Coastal Cur rent intruded to as far south as the water around Peng-Hu Islands. To com pare the El Nino/La Nina events with regard to SST and wind speed, we found that SST was warmer in the El Nino winters (1998, 2003-2005) than in the La Nina winters (1999-2001, 2008), and wind speed was more intensive in the La Nina winters (1996, 1999-2001, 2006, 2008) than in the El Nino winters (1998, 2003-2005, 2007). In the winter of 2008, the wind speed sharply in creased on 26 January and lasted for more than 30 days, with wind speed peaked at 7.36 ms^(-1). The monthly SST in February 2008 was about 7℃ lower than that of the 12-yearaver age. This decadal oscillation shows that the wind variation corresponds well with the El Nino/La Nina events, especially, the continuous strong wind in the La Nina winter of 2008. We thus suggest the influence of climate change on wind speed to be responsible for the change in the cur rent. The exceptional cold SSTs around Chang-Yuen Ridge and Peng-Hu Is lands in February of 2008 probably were, there fore, caused by the more south ward intrusion of China Coastal Current driven by the continuous strong wind.

Highlights

The Taiwan Strait is a shallow channel connecting the East China Sea in the north and the South China Sea in the south
By using AVHRR high-resolution (1.1 km) sea surface temperature (SST) data form 1996 - 2008, we were able to identify the exceptional intrusion of the China Coastal Current in the Taiwan Strait in the La Niña winter of 2008
The spatial distribution of cold and warm water is always bounded in the central Taiwan Strait

Summary

INTRODUCTION

The Taiwan Strait is a shallow channel connecting the East China Sea in the north and the South China Sea in the south. The. In winter, the flow patterns shown in Fig. 1 reveal that the main of China Coastal Current on the western side of the Strait was moving southward along the Chinese coasts. Previous studies (Lee et al 2003; Kuo and Ho 2004) examined the SST (sea surface temperature) patterns in the Taiwan Strait They showed that in wintertime the dominant spatial variance in sea surface temperature (SST) is consistent with a quasi-permanent front at the Chang-Yuen Ridge. Most of the previous studies suggest that the cold China Costal Current is blocked north of the Chang-Yuen Ridge in winter.

DATA AND METHOD

SST COMPOSITE MAPS IN WINTER

DISCUSSION

SUMMARY