16 - Seasonal variability of sea surface temperature in Southern Indian coastal water using Landsat 8 OLI/TIRS images

Abstract

The Southern Indian coastal water column is strongly influenced by seasonal changes of physical and chemical properties. In the present study, the Landsat 8 OLI/TIRS (thermal infrared sensor) images are used for estimating seasonal variability of sea surface temperature (SST) in the Southern Indian coastal water column. Satellite remote sensing of land and water surface temperature (L/WST) is used for many applications of earth and environmental studies. The performance of Landsat 8 TIRS is evaluated for retrieval of land surface temperature, and SST requires a systematic image calibrated method for radiometric and atmospheric correction followed by deriving L/WST products based on thermal emissivity properties. Three seasonal total internal reflection (TIR) images have been acquired for 2017–2018; these images are systematically processed to derive brightness temperature (BT) in order to measure SST at pixel scale (10 × 10m). To derive the SST, the formula used for this region is Ts=BT10+(2.946∗(BT10 – BT11)) – 0.038 (Ts is the surface temperature value (°C), BT10 is the BT value (°C) for band 10, BT11 is the BT value (°C) for band 11). The split-window algorithm model uses Landsat 8 TIRS bands 10 (TIR1) and 11 (TIR2) for estimating SST, and the root-mean-square error is estimated for three seasons within the range of 0.19–0.22 using INCOIS and buoys observed SST data that indicates low bias within the output of SST products. The result shows that the annual average value of SST is about 28.54°C during December, which slightly increases to 29.68°C and 29.70°C during March and September, respectively. The SST is at lower range along the nearshore during December and gradually increases toward the sea due to lower atmospheric temperature and cold current. Meanwhile, the SST is higher in coastal water along the nearshore as well as toward the sea during March and September; this is due to increases of land and sea atmospheric temperature and moving warm current along the shallow depth of near offshore areas.