A tidal correction model for near-infrared (NIR) reflectance over tidal flats

We examined the temporal variation of near-infrared (NIR) reflectance over tidal flats by proposing a tidal correction model for NIR reflectance. Sediment type, exposure time and interstitial and remnant surface waters play a key role in the optical surface reflectance of tidal flats. We established a tidal correction model for NIR reflectance by analysing 1015 scenes from the Geostationary Ocean Color Imager (GOCI), which is the first ocean colour sensor mounted on a geostationary satellite. The GOCI provides eight scenes per day with a 500-m resolution. Our results yielded two main findings. First, the reflectance model shows an asymmetric shape between ebb and flood tides. As the surface reflectance increases gradually during the ebb tide, the slope decreases steeply during the flood tide. Second, at least two models showing surface sediment are required. The tidal correction models for sand- and mixed-flats were similar; however, the one for mud-flats differed significantly. Our models work to correct for the tidal flat reflectance shown in optical images that were acquired under different tidal conditions.