Une méthode statistique de détermination de séquences caractéristiques dans une série temporelle de plusieurs variables. Application à la physico-chimie des eaux de l'étang de Berre

Abstract

Abstract Situated close to the French Mediterranean coast, the Berre lagoon is a brackish water lagoon highly disturbed by freshwater inputs coming from an hydroelectric power station. Since 1996, in the framework of an ecological program, a self sampling station hourly samples physicochemical variables such as temperature salinity and dissolved oxygen rates. This paper presents a statistical method that allows to summarize the dynamics of the water column with a sequence of daily typical states. This method takes into account the heterogeneity of the variables and keeps their temporal structure. Thus, the typical states are described by the hourly evolution of the distributions of each variable. Most of the time (74% of the observations), the water column is in a stratified state. The water column rocks to a mixed state under the effects of wind (19% of the observations). Transient days between these two states can be isolated in 7% of cases. Results show that the long-term system dynamics is not correlated with the daily environmental variations.