Global analysis of the lower tropospheric disturbances in the tropics during the northern summer of the FGGE year part II: Regional characteristics of the disturbances

Regional characteristics of the synoptic-scale wave disturbances in the tropical lower troposphere were examined by analyzing the FGGE level III-b data. Three tropical regions, western Pacific, eastern Pacific, and a region from the African Continent to the Atlantic, were selected for the present study. Spectrum analysis, trajectory analysis and composite analysis were used to obtain characteristics of the wave disturbances for each region.Main findings are as follows: 1.) The generation region of the western Pacific wave disturbances related to typhoon development are found around 5° N and 170° E. 2.) An interaction of the western Pacific wave disturbances with the upper Mid-Pacific trough was indicated statistically as an intensifying condition for typhoons. 3.) The wave disturbances in the eastern Pacific originate to the west of Panama and propagate west-north-westward with a period of 5.7 day and a wavelength of about 2700 km. 4.) The structure of the eastern Pacific wave disturbances is similar to that of the western Pacific disturbances. 5.) Two different paths of the African waves are found over the African Continent. The northern disturbance has a period of 4.4 days while the southern one has a period of 3.3–3.6 days. 6.) Disturbances along the northern path of the African waves are traced only to as far as 45° W, and those along the southern path are traced to the Caribbean Sea.