Analysis of high frequency temperature time series in the Seine estuary from the Marel autonomous monitoring buoy

Abstract

In the marine sciences, continuous monitoring systems have been regarded as very useful tools to provide continuous high frequency measurements of many parameters. We analyse here a high frequency time series of temperature measurements recorded every 10 min between 1997 and 2004 in the macro tidal Seine estuary (France) by a Marel buoy, an automatic monitoring network for littoral environment. We have adapted multi-scale data analysis methods to deal with the many missing values present in the time series. A power spectral density analysis is performed over time scales spanning 5 decades, from 20 min to more than 7 years. A scale invariant behaviour of the form ${E\left(f \right)\approx f^{-\beta}}$ with β = 2.2 is revealed for scales below 5 h. Over this scaling range, we have performed structure functions analysis, and shown that the Seine river temperature data exhibit turbulent-like intermittent properties, with multifractal statistics. The multifractal exponents obtained possess some similarities with passive scalar turbulence results.