A sequence of a snowstorm, a quasi-stationary convergence zone (Japan Sea polar airmass convergence zone, JPCZ) and a mesoscale coastal front (MCF) caused an extreme weather disaster along the Sea of Japan (SOJ) coast in northern Japan from January 7 to 11, 2021. To examine how the presence of the Changbai Mountains (CMs) affects these multi-scale successive phenomena, we conducted numerical simulations with and without modified topography of the CMs and their surrounding regions using a regional atmospheric model with a horizontal resolution of 4 km. Backward-trajectory analyses and an additional experiment that removed the sublimation process of snow were also performed to clarify the formation and maintenance processes of the MCF. The CMs lead to the structural change of the snowstorm developing over the SOJ, enhancement of the JPCZ, and formation of the MCF, affecting heavy snowfall in the SOJ coastal areas. The MCF, which is a mesoscale phenomenon smaller than the JPCZ, is formed and maintained by the monsoonal flows that detour from the north and south of the CMs. Several of the parcels that detour from north of the CMs intrude into the MCF through the boundary layer, which is thermodynamically modified by the heat and moisture supply from the sea, whereas the inland flows that penetrate the MCF from its south are composed of two major routes: one is the flow detouring from south of the CMs that crosses the high mountains on the mainland of Japan, and the other is the parcels detouring from north of the CMs that penetrate from the inland after they land on the northern coast. The difference in equivalent potential temperature between the inland flows and the monsoonal flow from the sea is responsible for the MCF formation. A cold pool near the surface also contributes to the prolonged MCF. Understanding of the CMs’ cascading effects on multi-scale phenomena from synoptic scale to mesoscale is necessary for the prediction of extreme weather disasters over Japan in winter.

自 1 月 7 日起，一系列暴风雪、准静止辐合带（日本海极地气团辐合带，JPCZ）和中尺度海岸锋（MCF）在日本北部的日本海（SOJ）沿岸造成极端天气灾害至 2021 年 11 月。为了研究长白山 (CM) 的存在如何影响这些多尺度连续现象，我们使用具有水平分辨率的区域大气模型对 CM 及其周边地区的地形进行了修改和不修改的情况下进行了数值模拟4公里。还进行了后向轨迹分析和消除雪升华过程的附加实验，以阐明 MCF 的形成和维持过程。CMs 导致在 SOJ 上空发展的暴风雪的结构变化、JPCZ 的增强、和 MCF 的形成，影响 SOJ 沿海地区的大雪。MCF是一种比JPCZ小的中尺度现象，是由从CMs南北绕行的季风气流形成和维持的。从 CMs 北部绕行的几个地块通过边界层进入 MCF，该边界层在热力学上受到海洋热量和水分供应的影响，而从其南部穿透 MCF 的内陆流由两个主要部分组成路线：一种是穿越日本大陆高山的CMs以南绕行的流量，另一种是CMs以北绕行的地块在北部海岸登陆后从内陆渗透。内陆气流和来自海洋的季风气流之间的等效位温差是 MCF 形成的原因。靠近地表的冷池也有助于延长 MCF。了解 CM 对从天气尺度到中尺度的多尺度现象的级联效应对于预测日本冬季极端天气灾害是必要的。