Large ensemble climate projections for Japan's Pacific side depict a greater increase in extreme high temperatures than in mean temperature, driven by changes in near-surface pressure arising from global warming. An exception to this pattern is the Kanto Plain, also on the Pacific side, for which a smaller increase is simulated. We investigated, using the large ensemble projections, the causes on this small increase and examined the variability in future-temperature projections focusing on surface winds at multiple extreme levels. Global warming causes cool air from surrounding areas to suppress the rise in extreme high temperatures over the plain, by contrasting changes in surface wind between inland and coastal areas of the plain: Intensified local advection inland draws cooler air from coastward regions, whereas synoptic-scale shifts in wind patterns channel high-latitude air toward coast areas. Under simulated temperature extremes of ∼10°C above the climatological mean, generation of a Foehn-type wind enhances the development of temperature extremes over the Kanto Plain, similar to other Pacific regions of Japan. Although such events are rare, their future thermal condition is anticipated to be more severe.

日本太平洋一侧的大型气候预测显示，由于全球变暖导致近地表压力变化，极端高温的增幅高于平均温度。这种模式的一个例外是关东平原，它也位于太平洋一侧，模拟的增幅较小。我们使用大型集合预测调查了这种小幅增加的原因，并检查了未来温度预测的变化性，重点关注多个极端水平的表面风。全球变暖导致周边地区的冷空气抑制了平原极端高温的上升，而平原内陆和沿海地区表面风的变化形成对比：内陆局部平流增强，从沿海地区吸入冷空气，而天气尺度上风型的变化则将高纬度空气引导向海岸地区。在模拟的极端温度比气候平均值高约 10°C 的情况下，焚风风的产生会促进关东平原极端温度的发展，与日本其他太平洋地区类似。尽管此类事件很少见，但预计未来的热状况会更加严峻。