Recent decades have been witness to the increase in the global frequency of extreme heat because of global climate change. Southern-Central Japan and South Korea are no exemptions to the extreme heat of which both experience simultaneously. A group of climatologists studied the wide-scale circulation that led to the simultaneous extreme heat of these two regions. Their findings have been published in the Journal of Climate.
"The concurrent extreme heat result from a deep anomalous anticyclone over East Asia, which induces anomalous subsidence and consequent higher surface temperature," said Ke Xu, the first author on the paper, who is a postdoc working with Prof. Riyu Lu and Prof. Jiangyu Mao in the Institute of Atmospheric Physics, Chinese Academy of Sciences.
Wave trains that come from upstream regions start the anomalous anticyclone that move eastward along the Asian westerly jet in the upper troposphere. "These wave trains can be categorized into two types that are characterized by the precursor anticyclonic and cyclonic anomalies, respectively, over central Asia," Xu said. "The two types of wave pattern are indicative to the occurrence of EH over South Korea and southern-central Japan."
The Asian westerly jet controls the distinction between these two kinds of wave train. "The Asian westerly jet, as the basic flow, can determine not only the propagation, but also the horizontal structure of the Rossby wave in terms of spatial scale and geographical distribution." Xu said.
This study identifies the unique traits of the circulation responsible for extreme heat in these two regions. Extreme heat wave patterns from other regions are different from those found in South Korea and Southern-Central Japan.
Other contributors include Prof. Baek-Jo Kim of the National Institute of Meteorological Sciences in South Korea, Prof. Jong-Kil Park and Prof. Jae-Young Byon of the Inje University in South Korea, Dr. Ruidan Chen of Sun Yat-sen University in China and Dr. Eun-Byul Kim of the Inje University in South Korea.
