Variability of Southern Hemisphere Cyclone and Anticyclone Behavior: Further Analysis

Alexandre Bernardes Pezza, Tércio Ambrizzi
2003 Journal of Climate  
This paper presents some additional results on the use of an automatic scheme for tracking surface cyclones and anticyclones. The Southern Hemisphere (SH) total amount of synoptic tracks (every 12 hours) was analyzed for the 1973 -1996 period using sea level pressure from the National Center for Environmental Prediction (NCEP) Reanalysis. Composites for seven El Niño (EN) and La Niña (LN) years were constructed in order to analyze the association between the hemispheric cyclone and anticyclone
more » ... ne and anticyclone propagation and the phase of the El Niño -Southern Oscillation phenomenon (ENSO). A climatological view of cyclone and anticyclone tracks and orphan centers superposed on the same map is presented and analyzed. A large area with overlapped cyclone and anticyclone tracks is seen between 30 o and 60 o S which is approximately the climatological position of the SH transient activity. To the north of 30 o S, the Subtropical South Atlantic High is embedded in a region with just a few cyclone tracks. This feature is not evident for the Pacific and the Indian's High. The subtropical cyclones dominate most of the west Pacific and north of Australia. Orographic and heat lows are well spread over the tropical regions of South America and Africa. Finally, the storm tracks region appeared as a very marked feature around the Antarctic continent. In accordance with some previous studies, the total number of the SH cyclones and anticyclones during the austral winter season has shown an overall decline, particularly at the end of the 1970s. Nevertheless, a more complex behavior shows up when the weak systems are eliminated and the intense end of the spectrum is analyzed. For the anticyclone tracks above 1020 hPa, there is still some tendency to an overall decline, but it is small and not statistically significant. For the stronger
doi:10.1175/1520-0442(2003)016<1075:voshca>2.0.co;2 fatcat:sx6ke7x33ndebfw5bqrmnknlze