Coastal Shallow Water Diurnal Warming

A good understanding of diurnal warming phenomenon is important for satellite sea surface temperature (SST) validation against in-situ buoy data and satellite data merging. For the coastal region, it also helps to improve the satellite data application to predict ecosystem health such as coral reef bleaching. Compared to its open ocean counterparts that have been studied extensively and modeled with good success, coastal diurnal warming is rarely studied. This study summarizes one of the first studies which attempts to study the coastal diurnal warming comprehensively, considering many aspects of coastal characteristics, including the influence of tidal impacts and geographic locations, using an integrated approach including in-situ data analysis, modeling and satellite SST analysis. 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 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 (\u3e5 ms-1) 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 \u3c 0.15K, and standard deviations of between 0.56K and 0.74K, 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