Long-Term Hindcast of Extreme Sea Levels Using Unstructured Grid Models and Parametric TC Models

The effect of climate change on sea levels has received much attention these days. In addition to the global mean sea level rise, increased events of storm surges and high waves are expected. We estimated global extreme sea levels using long-period reanalysis. First, historical total sea levels were simulated using an unstructured grid storm surge model ADCIRC and validated against the tide gauge data across the global coastlines. We used a high-resolution mesh particularly near the Japanese shorelines to capture their features well. JRA-55 and JRA-3Q global reanalysis were used as climate input for calculating accurate storm surges. In order to capture the structure of tropical cyclones, we used Holland parametric storm model considering super gradient wind in the reanalysis of wind and pressure field. Next, we confirmed that modeled elevations significantly agree with tide gauge levels at each gauge point. Finally, extreme value analysis evaluated extreme sea levels, which occur once per 10, 50, or 100 years, using monthly and annual maxima.