Climatology of Polar Lows over the Sea of Japan Using the JRA-55 Reanalysis

Abstract

Polar lows are intense meso-α-scale cyclones that develop over the oceans poleward of the main baroclinic zone. A number of previous studies have reported polar low formation over the Sea of Japan within the East Asian winter monsoon. To understand the climatology of polar lows over the Sea of Japan, a tracking algorithm for polar lows is applied to the recent JRA-55 reanalysis. The polar low tracking is applied to 36 cold seasons (October–March) from October 1979 to March 2015. The polar lows over the Sea of Japan reach their maximum intensity on the southeastern side of the midline between the Japanese islands and the Asian continent. Consistent with previous case studies, composite analysis demonstrates that the polar low development is associated with the enhanced northerly flow on the western side of a synoptic-scale extratropical cyclone, with the cold trough in the midtroposphere and with increased heat fluxes from the sea surface. Furthermore, the present climatological study has revealed two dominant directions of motion of the polar lows: southward and eastward. Southward-moving polar lows are steered by a strong northerly flow in the lower troposphere, which is enhanced on the western side of synoptic-scale extratropical cyclones, while the eastward-moving polar lows occur within a planetary-scale westerly flow in the midlatitudes. Thus, the direction of polar low motion reflects the difference in planetary- and synoptic-scale conditions

An objective global climatology of polar lows based on reanalysis data

“…The PL season in the Northwest Pacific and the North Atlantic are comparable, except for considerably fewer PL occurrences in the former region in March. In the Sea of Japan, PLs are mainly detected in December to February with few cases in autumn and spring, in good agreement with Yanase et al s*().…”

“…The 10th percentile of U 10 m for PLs is found to be 13.3 m s −1 , lower than the threshold of 15 m s −1 , which represents gale force, commonly used for detecting PLs from low‐resolution reanalyses (e.g. (Zappa et al , ; Yanase et al , )).…”

A Polar Mesoscale Cyclone Formed over the East China Sea and Developed into a Secondary Cyclone over the Northwestern Pacific — An Observational Case Study on 19-22 February 1975 —

“…PMCs developed usually over areas of large air-sea temperature difference, which caused large heat energy supply from the sea to the atmosphere. These climatological features of PMCs over the Japan Sea are consistent with results of many observational studies (e.g., Ninomiya 1991;Ninomiya et al 1993;Tsuboki and Wakahama 1992;Fu et al 2004), a climatological study (Yanase et al 2016), and numerical simulation studies (e.g., Yanase et al 2004;Yanase and Niino 2007).…”

North Atlantic polar lows and weather regimes: do current links persist in a warmer climate?

“…Businger, 1985;Noer and Ovhed, 2003), the convective heating driven by surface fluxes appears particularly well suited to distinguish between cyclones that will intensify into PL from non-intensifying systems (c.f. Bracegirdle and Gray, 2008;Yanase et al, 2016), and reveals areas where PL can form (Kolstad, 2011;Mallet et al, 2013). This heating can be successfully estimated from the difference of temperature (sometimes potential temperature) between the sea surface (SST) and the overlying atmosphere at either 700 hPa as in Bracegirdle and Gray (2008) or 500 hPa as in Noer and Ovhed (2003), Claud et al (2007), and Zahn and von Storch (2008a); in this case written as SST-T500.…”