Multi-scale analysis of the evolution of surface turbulent heat fluxes using continuous wavelet transform

Sensible (H) and latent (LE) heat are frequently studied forms of energy exchanges between an ecosystem and the atmosphere. They result from many underlying processes that may or not be linked. In order to identify these processes, this study investigates the evolution of both mentioned surface turbulent heat fluxes on an annual and multi-annual scale while taking their correlations into account. To perform such analyses, a continuous wavelet-based methodology is applied on a fourteen-year dataset of half-hourly fluxes of H and LE obtained by a micrometeorological method called eddy-covariance over a young beech forest at Hesse, North-eastern France. Both the Morlet and Mexican Hat wavelets are used, due to their respective characteristics and their suitability for investigating environmental fluxes. This study – held in the case of a Master thesis – aims, firstly, to bring new insights on well-known H/LE patterns and, secondly, to derive underlying correlations between processes governing heat exchanges over an ecosystem. At this stage, many wavelet-based results are available along with preliminary conclusions on the ecosystem’s behavior. This communication presents the context of the research accompanied by key results, including the coherence spectra between H and LE, and exposes some difficulties encountered in the identification of eco-physiological processes driving both fluxes evolutions.