Modes of atmospheric variability over the Southern Ocean

Abstract

The atmosphere over the Southern Ocean (SO) has been historically very poorly observed. Until fairly recently, the climate means of important parameters were known only imperfectly. In the modern era, new sources of data, particularly a wide range of products to come from remote sensing, have alleviated this problem. In addition to these developments, the advent of "data assimilation" and the conduct of "reanalyses" now means that available data may be used in "optimal" ways to obtain meteorological analyses of a quality not available heretofore. This solid base means that we are now for the first time able to confidently document and understand the rich variety of modes of variability over the region. In this paper, we examine aspects of SO atmospheric variability and focus particularly on those associated with the mean sea level pressure (MSLP) in the 40-year National Centers for Environmental Prediction (NCEP) reanalysis. Discussion is devoted to many aspects of the behavior of cyclonic systems over the Ocean and the variabilities and trends shown in these. Of the variabilities also explored here are those associated with the high-latitude mode, the semiannual oscillation (SAO), and the Antarctic circumpolar wave (ACW). A wide range of physical processes drives these features and their variability and we investigate some of these here.