Southern Hemisphere strong polar mesoscale cyclones in high-resolution datasets

作者：Pezza Alexandre^*; Sadler Katherine; Uotila Petteri; Vihma Timo; Mesquita Michel D S; Reid Phil

来源：Climate Dynamics, 2016, 47(5-6): 1647-1660.

DOI：10.1007/s00382-015-2925-2

• Mesoscale cyclones
• Explosive cyclones
• Polar lows
• Sea ice
• Antarctica

Mesoscale cyclones are small low-pressure systems (usually < 500 km in radius) that often appear embedded in synoptic structures. These events can be weak and short lived or vigorous and destructive. Here we use an automatic tracking scheme to investigate two subsets of Southern Hemisphere mesoscale cyclones that are strong and have the potential to cause damage, namely "polar lows" (i.e., strong and short lived) and "explosive cyclones" (i.e., rapid intensification but not necessarily short lived). A short climatology (2009-2012) is obtained by using high resolution (0.5A degrees) Antarctic Mesoscale Prediction System (AMPS) mean sea level pressure. The results show a significant improvement of spatial detail compared to the 0.75A degrees resolution ERA-interim dataset, with a total count approximately 46 % higher in AMPS. The subset of mesoscale cyclones that are explosive is small, with a total genesis number of about 13 % that of polar lows. In addition, only about 1 % of the polar lows are explosive, suggesting that cyclones that undergo rapid intensification tend to become larger longer lived (and hence are no longer regarded as polar lows). Mesoscale cyclones are more frequent in winter, with a maximum concentration around the Antarctic but also occurring as far north as Tasmania and New Zealand. Analysis of sensible heat flux and sea ice extent anomalies during the genesis days shows that there is a large spread of genesis points over both positive and negative flux anomalies in winter, with a somewhat random pattern in the other seasons.

• 出版日期2016-9