Local Spectral Energetics Analysis of the Formation of Pacific Blocking Anticlones using an Orthonormal Wavelet Expansion.

Abstract

In this study, an orthonormal wavelet expansion along a latitudinal circle is applied to decompose atmospheric data into a series of wavelet components with different spatial scales, and longitudinal locations. The application of the local spectral energetics allows the investigation of the local energy transformations for the local structures in the atmosphere. By applying the local spectral energetics analyses to 10 events of the Pacific blocking, we find that different energy conversion terms contribute to the increase of eddy kinetic energy during the development of the blocking events. For 8 out of 10 blocking events, the gain of energy through the wave-wave interaction of eddy kinetic energy is the most important process for the onset of blocking. The intensified trough of the blocking scale which is located at the western side of the blocking and the synoptic disturbances around the blocking, especially the western side, to convert eddy kinetic energy into the other components through the wave-wave interaction. The local spectral energetics analysis demonstrates that the wave-wave interaction of the eddy kinetic energy of the planetary-scale, and synoptic disturbances, at the western side of the blocking anticyclone plays an important role for the formation, and development of the atmospheric blocking. The behavior of the wave-wave interaction of the eddy kinetic energy in terms of the scale and longitudinal location is essentially consistent with the eddy straining hypothesis at the western side of the blocking.