Storm surges and atmospheric circulation: an analysis since 1950 for the Belgian coast and forecast for the 21st century

At daily time scale during the period 1950-2000, sea-surge heights at Oostende tide-gauge station are quasi-linearly correlated with the Sea-level pressure (SLP) over the Baltic Sea. High sea surges along the Belgian coast occur when a low pressure system remains stationary over Scandinavia and is associated with a reinforced Azores high. This SLP pattern favors strong onshore winds from Northwest sectors in the southern part of the North Sea, and the piling up of water along the Belgian coast. A statistical downscaling method is used to set-up a model to relate SLP to sea surge at Oostende. Linear regressions are designed to relate the daily surge height at Oostende with (i) the daily SLP over the Baltic Sea, (ii) the daily value of the pressure gradient between the Baltic Sea and the Azores and (iii) both of these atmospheric parameters. The multiple linear regression robustly reproduces the interannual to long-term variability of high surges at Oostende. This linear regression is then used with SLP time series simulated until 2100 under SRES scenario A1b, A2 and B2. High surges (at least up to the 99th percentile of the daily values) are expected to stay stationary during the 21st century, associated with no significant changes in SLP conditions over the Baltic Sea and over the Azores.