Sea Level Extremes Analysis

This product includes a set of scripts developed in Matlab (Version R2021a), aimed at identifying and analysing the extreme events of a series of sea level anomalies (SLA, e.g. from a tide gauge). The sampling frequency can be minutes or hours. The main function is "extreme_analysis.m", which takes as input the sea level anomaly series, and the atmospheric component of sea level series. As input, it is also required to specify the percentile that will be used to identify the extreme values, and the minimum separation between events that will be considered. Optionally, it is possible to load seasonal cycle and astronomical tide series, or make the function calculate it. In case the tide has to be calculated, it calls the UTIDE functions (Codiga 2023: https://es.mathworks.com/matlabcentral/fileexchange/46523-utide-unified-tidal-analysis-and-prediction-functions) which must be in the same directory as the main function. It identifies the extreme events of the series, stores their parameters (start and end date of each event, date of the peak, SLA at peak time, duration and average SLA during the event) and calculates the contributions of the different processes considered, which are: low-frequency atmospheric contribution, storm surge, seasonal cycle, astronomical tide, residuals T>1m, residuals 1h<T<1m and residuals T<1h. The separation into frequency bands (the atmospheric component in LFAC and storm surge, and that of the residuals), is carried out with a Butterworth filter of order 3 (can be modified), by calling the external function "butter_filter.m", which must be in the same directory.