Evidence for a mid-latitude, mesoscale downscale energy cascade from the marine boundary layer

The third-order longitudinal velocity structure function S LLL and the longitudinal and transverse second order structure functions S LL (r) and S T T (r) are determined for the marine boundary layer over the Pacific Ocean. The velocities are the 10 meter equivalent neutral winds taken from scatterometer measurements by SEAWINDS on the QuikSCAT satellite. The sign of S LLL is used to infer the direction of the energy cascade, with S LLL 0 indicating an upscale energy cascade. This is analogous to how S LLL would behave in three-and two-dimensional turbulence respectively, but does not imply that either of these dy-namical systems is completely applicable. The analysis of structure 1 functions over the north Pacific Ocean has been divided into latitu-dinal and longitudinal boxes due to a variety of geophysical effects. This paper will concentrate on mid-latitude, mid-Pacific longitudes because these boxes are least influenced by the equatorial waveguide and large sea surface temperature gradients and currents. The overall conclusion is that for lengths r less than 250 km S LLL 0 is favored. In this sense the results are consistent with upper tropospheric aircraft mea-surements and recent numerical results for the developing theory of stratified, rotating turbulence. The complete northern Pacific results will be presented in another paper