The coastal sea surface temperature changes near the nuclear power plants of northern Taiwan observed from satellite images

Abstract

In order to estimate the thermal plumes discharged from Chinshan and Kuosheng nuclear power plants on the coast of north Taiwan, this study uses the thermal infrared data from Landsat 7 ETM+(Enhanced Thematic Mapper Surface Temperature) to contrast with the in-situ SST measurement for the intake/discharge ports of the nuclear power plants. The near-infrared (band 4) data of Landsat 7 ETM+ are firstly applied to distinguish ocean and land, and then the thermal infrared (band 6) data are used to estimate SST. The algorithm of SST on north Taiwan is established in this study by the contrast between the in-situ SST data of the two nuclear power plants and the thermal infrared data of Landsat 7 ETM+. The standard deviation of SST retrieved through this algorithm is estimated to be 3.1°C, but the mean difference is near 0. According to the retrieved SST from the satellite data, the warm-plume (>4°C than offshore SST) discharge of Chinshan nuclear power plant reaches 540-1080 m far from its discharge port, but for Kuosheng Nuclear Power Plant, the farthest of the warm-plume discharge from the discharge port is 390-900 m. The retrieved SST gradually gets cooler by diffusion from the discharge port to the offshore. Apparently, the Landsat 7 ETM+ can be applied to measure the special variance of SST. The result also shows the area of significant thermal plume (>4°C than offshore SST) are about 0.01-1.3 km 2 and 0.09-8.53 km 2 for the Chinshan and Kuosheng nuclear plants respectively. Moreover, the significant thermal plume area is affected by tides. During the flood tide, the warm-plume discharge gets close to the coast, and it will make the significant thermal plume area increase. Besides, the second significant thermal plume (>2°C than offshore SST) is also increased during the ebb tide because the thermal plume may be taken away and diluted from the discharged port. However, due to different topographies, the area of thermal plume of the Kuosheng is broader than that of Chinshan nuclear power plant.