Quasi-stationary waves in the southern hemisphere during El Nina and La Nina events

• Published in: Annales geophysicae (1988) Vol. 22; no. 3; pp. 789 - 806
• Main Authors: Rao, V B, Fernandez, JPR, Franchito, SH
• Format: Journal Article
• Language: English
• Published: 01.01.2004
• Subjects: Marine
• ISSN: 0992-7689

Characteristics of quasi-stationary (QS) waves in the Southern Hemisphere are discussed using 49 years (1950-1998) of NCEP/NCAR reanalysis data. A comparison between the stationary wave amplitudes and phases between the recent data (1979-1998) and the entire 49 years data showed that the differences are not large and the 49 years data can be used for the study. Using the 49 years of data it is found that the amplitude of QS wave 1 has two maxima in the upper atmosphere, one at 30degrees S and the other at 55degrees S. QS waves 2 and 3 have much less amplitude. Monthly variation of the amplitude of QS wave 1 shows that it is highest in October, particularly in the upper troposphere and stratosphere. To examine the QS wave propagation Plumb's methodology is used. Higher upward propagation indicates higher energy transport. A clear wave train can be identified at 300 hPa in all the seasons except in summer. The horizontal component of wave activity flux in the El Ni (n) over tildeo composite seems to be a Rossby wave propagating along a Rossby wave guide, at first poleward until it reaches its turning latitude in the Southern Hemisphere mid-latitudes, then equatorward in the vicinity of South America. The position of the center of positive anomalies in the austral spring over tildeo years over the southeast Pacific, near South America, favors the occurrence of blocking highs in this region. This agrees with a recent numerical study by Renwick and Revell (1999).