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A new reference data set of mesocyclone activity over the Southern Ocean has been developed from the manual analysis of high-resolution infrared satellite mosaics for winter 2004. Of the total 1735 mesocyclones which were identified and analyzed, about three quarters were classified as being "polar lows" (i.e., intense systems; see Rasmussen and Turner, 2003). The data set includes mesocyclone track, size, associated cloud vortex type, and background synoptic conditions. Maxima in track density were observed over the Bellingshausen Sea and around East Antarctica and are highly correlated with cyclogenesis regions. A comparison against QuikSCAT and reanalyses wind characteristics shows that the reanalyses, while capturing mesocyclone events, tend to considerably underestimate their wind speed (by up to 10ms(-1)). This mesocyclone data set is available as a reference for further analysis of mesocyclones and for the evaluation and development of cyclone-tracking algorithms.

Plain Language Summary Mesocyclones in high latitudes are important maritime atmospheric phenomena, they characterize by strong wind speeds and surface fluxes despite their small sizes (200 to 1000 km) and short lifetime (6 to 36 hours). These characteristics make their identification and tracking difficult in global reanalyses, consequently, they are still poorly documented and quantified, especially, in the Southern Hemisphere. Number of studies demonstrated an overview of mesocyclone activity over the Southern Hemisphere. These studies are based both on automated identification and tracking algorithms and on manual identification and tracking (mostly regional) and show inconsistent assessments. To clarify the Southern Hemisphere mesocyclone activity and to provide a reference dataset, that may be used to validate automated tracking schemes in the Southern Hemisphere we here present manually identified and tracked database of mesocyclones over the Southern Ocean for winter 2004. This database is used to assess the ability of four modern reanalyses to reproduce mesocyclones wind speed field structure in comparison with QuikSCAT scatterometer wind data.