The seasonality and locality of low frequency oscillation by wavelet analysis

Morlet wavelet analysis and other statistical methods are applied to investigate the seasonality and locality of the low frequency oscillation (LFO) in the atmosphere based on the horizontal winds at 850 hPa and 200 hPa from NCEP/NCAR reanalyses I data. The analyses are conducted in four different areas including Indian Ocean, the tropical western Pacific, the western Pacific subtropical high area and the Ural- Okhotsk belt. The results show that significant seasonal variations exist in above mentioned areas. These seasonal variations are mainly defined as four patterns, namely, the period variation from long to short period (Pattern I), the period change from short to long period (Pattern II), the inconspicuous period variation (Pattern III), and branching wavelet energy (Pattern VI). In addition, an interesting phenomenon, the branching WE, exists in all seasons and areas. Moreover, the variations of the LFO and its period change with space are found in the same season.