Climatology of Anticyclonic and Cyclonic Rossby Wave Breaking on the Dynamical Tropopause in the Southern Hemisphere

Abstract

Abstract The characteristics of the climatological distribution of the anticyclonic (LC1) and cyclonic (LC2) Rossby wave breaking (RWB) in the Southern Hemisphere (SH) are investigated by calculating the occurrence frequency of the LC1- and LC2-like stratospheric potential vorticity (PV) streamers in the SH during the austral summer [December–February (DJF)] and wintertime [June–August (JJA)] on several isentropic surfaces by using the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) daily dataset. The results show that 1) on the equatorward flank of the climatological midlatitude jet (MLJ), the LC1-like PV streamers are frequently found over the central oceanic regions, whereas the LC2-like PV streamers are almost absent. On the poleward flank of the climatological MLJ, both types of PV streamers are frequently observed and the LC2-like PV streamers predominate; 2) the regions where the occurrences of the PV streamers are frequent overlap the weak zonal wind regions; and 3) in austral winter, a “double-jet” setting is evident in two regions of the SH [the double-jet upstream (DU) and the spilt jet region]. In the double-jet setting regions, the LC1-like PV streamers are frequently found both in the DU and the split-jet regions, while the occurrence of the LC2-like PV streamers is frequent in the split-jet region but is rather infrequent in the DU region.