Multidecadal and interannual changes of stationary Rossby waves



Changes in stationary Rossby waves (SRW) are connected to regional climate change and the propagation of these waves has a large influence on the evolution and development of the general circulation. Since the late 1970s and early 1980s many studies have noted a major shift in the structure of large-scale circulation occurring in both hemispheres. This paper explores the changes in the SRW pattern and their propagation associated with these climate shifts. First, multidecadal changes in SRW activity are examined, using NCEP-NCAR reanalysis data, for two periods: 1948–1978 and 1979–2000. For comparison of these two periods, the zonal wind, SRW kinetic energy pattern along the waveguide and stationary wavenumber (Ks) are analysed. The results showed that in the Northern Hemisphere (NH) the SRW propagation is favoured in the Asian jet stream (AJS) waveguide (Ks = 7) in the period 1979–2000, mainly in the east Asia region. There are indications that this could be associated with the Pacific Decadal Oscillation warm phase. A favoured SRW propagation also occurs in the North Atlantic subtropical jet (NASJ) waveguide (Ks = 5) region in the latter period and could be linked with positive North Atlantic Oscillation. In the Southern Hemisphere (SH), a favoured SRW propagation in the polar jet waveguide (Ks = 4) region is observed in the latter period and this could be associated, indirectly, with tropical sea surface temperature fluctuations. The interannual changes in the SRW propagation during stronger El Niño and La Niña events, which occurred from 1948 to 2000 are then examined. The results showed that, during stronger El Niño events, in NH the SRW propagation in the AJS, mainly in the east Asia region, and in the NASJ waveguides (Ks = 7, 5, respectively) is reduced. On the other hand, in SH the SRW propagation in Australian and polar waveguides (Ks = 7, 4, respectively) is favoured. Copyright © 2011 Royal Meteorological Society