Southern Ocean mesocyclones and polar lows from manually tracked satellite mosaics

Abstract

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 10 m s−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.

Numerical simulation of subsynoptic-scale cyclogenesis around an idealized Antarctic continent

“…A near-surface strong temperature gradient developed near the katabatic confluence zone, and near where the subsynoptic low pressure developed and the streamlines spiral to form a cyclonic circulation. Close examination suggests stronger wind speed at the adge of the low pressure, which concurs with Verezemskaya et al (2017) observations. The main role of the topography is that orography troughs act as convergence zone for the descending katabatic windflow, this cold air mass interacts with warmer environment once arriving to the ocean adjacent to the coast.…”

“…After the fifth days, eight subsynoptic-scale cyclonic features have developed around the simulated continent, offshore the topographic troughs. These cyclonic centers show a westward displacement, similar movement has been shown by observational studies around Antarctica carried out by Carrasco et al (2003), Pezza et al (2016), Verezemskaya et al (2017), and others. A near-surface strong temperature gradient developed near the katabatic confluence zone, and near where the subsynoptic low pressure developed and the streamlines spiral to form a cyclonic circulation.…”

Deep Convolutional Neural Networks Capabilities for Binary Classification of Polar Mesocyclones in Satellite Mosaics

“…For the training of DCNNs, we use the MCs dataset for the Southern Ocean (SOMC, http://sail.ocean.ru/antarctica/), consisting of 1735 MC trajectories, resulting in 9252 MC locations and associated estimates of MC sizes [5] for the four-months period (June, July, August, September) of 2004 ( Figure 1a). The dataset was developed by visual identification and tracking of MCs using 976 consecutive three-hourly satellite IR (10.3-11.3 micron) and WV (~6.7 microns) mosaics provided by the Antarctic Meteorological Research Center (AMRC) Antarctic Satellite Composite Imagery (AMRC ASCI) [54,55].…”

“…As these examples illustrate, most studies of MCs activity are regional [10,17,18,31,32] and they cover relatively short time periods [5] due to the very costly and time-consuming procedure of visual identification and tracking of MCs. Thus, development of the reliable long-term (multiyear) dataset covering the whole circumpolar Arctic or Antarctic remains a challenge.…”

“…The paper is organized as follows. Section 2 describes the source data based on MC trajectories database [5]. Section 3 describes the development of the MC detection method that is based on deep convolutional neural networks and necessary data preprocessing.…”