Climatological aspects of Hadley, Walker and monsoon circulations in two phases of the Pacific Decadal Oscillation

Summary Reanalyzed 200 hPa velocity potential (χ) fields for the 1958–2005 period are used to examine the influences of the Pacific Decadal Oscillation (PDO) in the average Hadley, Walker and monsoon circulations. These circulations are quantified and separated from each other by computing their components contained in the 200 hPa χ fields for the 1958–1976 and 1977–1995 periods. The main results found here are that the Hadley and monsoon circulations show small differences between the two periods, while the Walker circulation shows weaker action centers during the second period, with its center in the western Pacific being located further west. The differences in intensity and locations of the main action centers of the Walker circulation between the first and second periods are analyzed here in terms of the PDO influences. Authors’ address: Mary T. Kayano, Samia R. Garcia, Instituto Nacional de Pesquisas Espaciais/CPTEC, Avenida dos Astronautas 1758, 12227-010 S?o José dos Campos, SP, Brazil.