Japanese society has recently taken a greater interest in foehn warming because it has caused record-breaking high temperatures and sudden damage to rice crops. This is the first comprehensive climatological study focused on Japan's south foehn, which blows across the Toyama Plain in the Hokuriku region. Climatological analyses, including an objective self-organizing map and subjective analysis of 198 south foehn cases, revealed that ~68.2% of the foehns occurred while an extratropical cyclone was passing through the Sea of Japan. Approximately 19.7% of the remaining foehns blew while an anticyclone covered Japan. Only 5.1% of all foehns occurred during a typhoon, but very high temperatures occurred when typhoons were approaching. Foehns were observed in all seasons but tended to blow more often in spring, when there are many migratory anticyclones and cyclones. Most of the foehns begin at night and end or pause during the day. This is due to the removal of the nocturnal stable layer and the development of a local daytime pressure gradient on the lee side. The dynamical mechanism provides the primary explanation for Japan's south foehn. Surprisingly, the foehns with precipitation on windward mountains slopes accounted for only ~19.2% of all cases, with ~40.0% being typhoon cases. Most of these are likely of multiple type; a pure thermodynamical type of foehn is a rare occurrence. Numerical simulations and back trajectory analyses for 76 selected foehn cases revealed that the majority of the air parcels originated from the south and passed straight over the Hida Highlands, between two mountain ranges, as a hybrid type of gap and foehn winds.

中文翻译：

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日本富山平原上的南焚风：动力机制还是热力学机制？

日本社会最近对焚风变暖产生了更大的兴趣，因为它造成了创纪录的高温和对水稻作物的突然破坏。这是第一次以日本的南焚风为重点的综合气候学研究，它吹过北陆地区的富山平原。气候分析，包括对 198 个焚风南部案例的客观自组织图和主观分析，显示约 68.2% 的焚风发生在一个温带气旋穿过日本海时。大约 19.7% 的剩余焚风在反气旋覆盖日本时被吹灭。只有 5.1% 的焚风发生在台风期间，但当台风接近时，温度会非常高。在所有季节都可以观察到焚风，但往往在春季更频繁地吹，当有许多迁移性反气旋和气旋时。大多数焚风在夜间开始，在白天结束或暂停。这是由于夜间稳定层的去除和背风侧局部白天压力梯度的发展。动力机制为日本的南方焚风提供了主要解释。令人惊讶的是，在迎风山坡上有降水的焚风仅占所有案例的~19.2%，其中~40.0% 是台风案例。其中大多数可能是多种类型；纯粹的热力学类型的焚风是罕见的。对选定的 76 个焚风案例进行的数值模拟和反向轨迹分析表明，大部分气团来自南方，并作为间隙风和焚风的混合类型直接穿过飞騨高地，在两个山脉之间。