Spectral analysis of QuikSCAT surface winds and two-dimensional turbulence

A spectral decomposition of QuikSCAT surface wind vectors reveals different levels of variance and different values of the spectral slope in various regions of the world ocean for the 12 months investigated. The traditional considerations on the factors affecting the shape of the spectra are reviewed and compared to the results. In particular, the influence of large-scale synoptic systems is shown by comparing the steeper and more energetic spectra of the midlatitudes to the shallower spectra of the tropics. Similarly, the signature of convection is investigated by comparing spectra in the tropical convectively active and dry zones of the Pacific Ocean. Spectra of vorticity and divergence are calculated, along with spectral vorticity-to-divergence ratios. Their spatial and temporal variations are discussed. It is hypothesized that when convection is enhanced in the tropics, the spectral analysis captures the mesoscale/synoptic structures in which convection is embedded and that the spectra exhibit some of the characteristics of their midlatitude counterparts (i.e., steeper and more energetic).