Coastal Shallow Water Diurnal Warming: A Comprehensive Study Using In-Situ Data, Satellite Data and Modeling

Understanding diurnal warming is important for satellite sea surface temperature (SST) validation and data merging. For coastal region, it also helps to predict coral reef bleaching. This study summarizes one of the first comprehensive coastal diurnal warming studies using an integrated approach including in-situ and satellite data analysis, as well as modeling. First, two in-situ datasets at the Caribbean Sea and at the Great Barrier Reef region were studied. We found that most stations have clear diurnal warming signals at sub-surface depths. Similar to open ocean cases, the warming is influenced by wind and insolation. Coastal tidal impact on warming was quantified and found to be limited. Water depths, station reef types, and relative locations of the station to the the barrier reef chain in the east-west direction were found to affect the warming significantly. Second, three one-dimensional diurnal warming models are used for simulation. The simple ‘box model’ predicts the warming amplitudes best during strong and intermediate (> 5 ms) wind speeds while the POSH (Profiles of Ocean Surface Heating) model predicts the low wind warming best, though the modeled heat does not penetrate sufficiently downward. Finally, coastal SST from polar-orbiting and geostationary satellites are tested. Comparing SST against in-situ data yielded bias of < 0.15 K, and standard deviations of between 0.56 K and 0.74 K, similar or better than previous studies. Geostationary data captures diurnal warming well both in amplitudes and timing, while polar data captures the warming with various degree of success.