  The Hilbert-Huang transform is applied to analyze single particle Lagrangian
velocity data from numerical simulations of hydrodynamic turbulence. The
velocity trajectory is described in terms of a set of intrinsic mode functions,
C_{i}(t), and of their instantaneous frequency, \omega_{i}(t). On the basis of
this decomposition we define the \omega-conditioned statistical moments of the
C_{i} modes, named q-order Hilbert Spectra (HS). We show that such new
quantities have enhanced scaling properties as compared to traditional Fourier
transform- or correlation-based (Structure Functions) statistical indicators,
thus providing better insights into the turbulent energy transfer process. We
present a clear empirical evidence that the energy-like quantity, i.e. the
second-order HS, displays a linear scaling in time in the inertial range, as
expected from dimensional analysis and never observed before. We also measure
high order moment scaling exponents in a direct way, without resorting the
Extended Self Similarity (ESS) procedure. This leads to a new estimate of the
Lagrangian structure functions exponents which are consistent with the
multifractal prediction in the Lagrangian frame as proposed in [Biferale et
al., Phys. Rev. Lett. vol. 93, 064502 (2004)].
