Tsukuba, Japan—Extratropical cyclones traveling along the Kuroshio in East Asia, called "Kuroshio cyclones," bring heavy rain and snowfall in populated and industrial areas in East Asian countries. They considerably affect societies and economic sectors, including agriculture, transportation, logistics, and renewable-energy-based power generation sectors. Although extratropical cyclones in East Asia are known to occur frequently in spring, the reason behind this seasonality is not yet clarified.
The research group previously developed a method for objectively identifying mobile high- and low-pressure systems from global atmospheric data to elucidate the mechanism underlying the seasonality of extratropical cyclones and recent changes in high- and low-pressure systems in the North Pacific. In the current study, the researchers employed the method to four-dimensional atmospheric data spanning several decades. Results indicated that the activity of the "Kuroshio cyclones" peaks in spring because the low-level jet stream around the East China Sea is intensified by air over Eurasia in the west of Japan warmed from winter to spring, facilitating the formation of low-pressure systems.
A better elucidation of the mechanism underlying the seasonality of extratropical cyclone activity in East Asia can improve our understanding of the changes in the climate system around the region under the global warming scenario and improve the accuracy of seasonal forecasts in East Asian countries.
