Lagrangian drifter paths and length scales in the tropical Pacific warm pool from 1990 to 1991: with application of fractal techniques

Abstract. This paper presents an analysis of WOCE/TOGA surface drifter paths and its interpretation in conjunction with the west Pacific warm pool water motion. Our interest here lies in the existence of scale invariance in the observed data sets. The analysis proceeds by detecting scale invariance in the drifter paths data, and interpreting the invariance in terms of the statistical second order moment. The range of constant scaling exponent was found to be between 5 days and 10 days, and this range corresponded with the "long tail" of the temporal correlation function in the zonal direction. Velocity covariances in both the zonal and meridional directions were computed, and corresponding diffusivities were 8100 m²/sec meridionally and 41000 m²/sec zonally.
Considering the existence of large scale mean flow, it is thought that self-similar energy cascade processes associated with constant scaling exponent may be responsible for the anomalous zonal diffusivity, while the meridional diffusivity may be approximated by ordinary Brownian processes. We suggest that the scale invariance of the WOCE/TOGA surface drifter paths may be a manifestation of energy cascade processes from large scale mean flow to smaller scale irregular flow that is represented by fractional Brownian motion in the zonal direction.