Abstract: In order to establish a sufficient available data both for the spatial coverage and temporal duration, the reflectance data of three satellites of Aqua, Terra and SeaWiFS from July 27 to August 8, 2006 were merged by linear regression. A coastal water extension process was analyzed with the established data in the area adjacent to the Changjiang River Estuary. The results show that there is an obvious extension process from July 27 to August 8, 2006. During the extension process, the remote sensing reflectance of the coastal water decreases with the increase of distance from shore, the coastal water tongue extends almost in the east-west direction. According to the spatial coverage of reflectance and its concentration, the whole process is further divided into two stages, i.e., an eastward growing period from July 23 to August 2, and a westward extinction period from August 3 to August 8. During the eastward growing period, the coastal water tongue extends gradually to the east along the latitude of 32.4°N, and reaches the east-most longitude of 124.4°E. On the way to east, the coastal water tongue gradually narrows its shape and decreases its concentration. The moving speed of the tip of coastal water tongue boundary changes from 17.6 km/d to 33.4 km/d, with an average speed of 24.5 km/d. During the westward extinction period from August 3 to August 8, the coastal water tongue is getting narrow as well as decreasing concentration as a whole, but remains the spatial position unchanged. Based on the preliminary analysis of the mechanism of such process, it is believed that the tidal current would constrain the movement of coastal current along the coastal during the eastward growing period. The southerly wind during the eastward growing period and the easterly wind during the westward extinction period are found most-likely to be the cause of the coastal water extension process.

Key words: Changjiang diluted water, coastal water tongue, remote sensing reflectance, short-term extension process