Monitoring Variation in Sea Surface Temperature in the Nakdong River Estuary, Korea, Using Multiple Satellite Images

Abstract

Annual and monthly sea surface temperatures (SSTs) of the coastal waters around Nakdong River, Korea, were analyzed using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat. SST values derived from MODIS data were consistent with the in-situ data (R-2 = 0.63), whereas Landsat-derived SST values were moderately correlated with in-situ data (R-2 = 0.44). The mean annual SST over 18 years was 21.7 degrees C. The coldest temperatures were recorded in 2001, and the warmest were recorded in 2016. SSTs were higher during the summer than in the winter, mainly because of higher air temperatures in summer. Across all years, March was the coldest month, with a mean SST of 14.4 degrees C, whereas August was the warmest month at 28 degrees C. As MODIS data have a spatial resolution of 4 km, it cannot be used to detect SST variation at fine spatial scales (least 100 m or less). However, it can be monitored temporal trends in SST. Spatially detailed SST variation was monitored using Landsat data. According to the Landsat data, warm SSTs were measured in the area extending from the southwest to northeast of the Nakdong Estuary, which is an area affected by the Kuroshio Current. Climate data are needed in addition to image data to accurately monitor SST variation in the future.