Characteristics of cyclone climatology and variability in the Southern Ocean

Abstract

A new climatology of cyclones in the Southern Ocean is generated by applying an automated cyclone detection and tracking algorithm (developed by Hodges at the Reading University) for an improved and relatively high-resolution European Centre for Medium-Range Weather Forecasts atmospheric reanalysis during 1979–2013. A validation shows that identified cyclone tracks are in good agreement with a available analyzed cyclone product. The climatological characteristics of the Southern Ocean cyclones are then analyzed, including track, number, density, intensity, deepening rate and explosive events. An analysis shows that the number of cyclones in the Southern Ocean has increased for 1979–2013, but only statistically significant in summer. Coincident with the circumpolar trough, a single high-density band of cyclones is observed in 55°–67°S, and cyclone density has generally increased in north of this band for 1979–2013, except summer. The intensity of up to 70% cyclones in the Southern Ocean is less than 980 hPa, and only a few cyclones with pressure less than 920 hPa are detected for 1979–2013. Further analysis shows that a high frequency of explosive cyclones is located in the band of 45°–55°S, and the Atlantic Ocean sector has much higher frequent occurrence of the explosive cyclones than that in the Pacific Ocean sector. Additionally, the relationship between cyclone activities in the Southern Ocean and the Southern Annular Mode is discussed.