SEA-EFFECT PRECIPITATION: A LOOK AT JAPAN'S "GOSETSU CHITAI".

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Date: Feb. 2020
Publisher: American Meteorological Society
Document Type: Report
Length: 2,691 words
Lexile Measure: 1480L

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Portions of Honshu and Hokkaido Islands of Japan experience remarkable snowfalls during the East Asian winter monsoon, when frequent cold-air outbreaks occur over the Sea of Japan (also called the East Sea). Mean annual snowfall in this "Gosetsu Chitai" (heavy snow area) exceeds 600 cm (235 in) in some nearsea-level cities and 1,300 cm (512 in) in some mountain areas. Snow depths can reach 2 m near sea level and 7 m in the mountains, with the snow corridor along the Tateyama Kurobe Alpine Route in the Hida Mountains (a.k.a. northern Japanese Alps) famous for its towering snow walls when it opens each spring. While snowfall is most prolific in Japan, some coastal areas of Korea, Russia, and China observe less frequent but high-impact snowstorms produced by the Sea of Japan or the Yellow Sea.

There is a rich history of cloud microphysical research in Japan and an extensive literature examining sea-effect precipitation and its impacts in Japan and East Asia. But this literature is often overlooked by North American meteorologists. Furthermore, collaborations between Japanese and North American scientists investigating sea- and lake-effect precipitation have been limited. To stimulate such collaboration, we introduce North American meteorologists to the snow climate of western Japan, summarize contemporary knowledge concerning sea-effect precipitation in the region, and make comparisons to lake-effect precipitation of the North American Great Lakes.

Regional climate

Mean sea surface temperatures (SSTs) in the Sea of Japan generally decline westward and poleward, with warmer water where the Tsushima current flows along the west coast of Honshu and colder water where the Liman current flows along the Asian coast. During December, SSTs generally increase eastward from the Asian coast. SSTs decline 2-5[degrees]C by February, with the smallest decline near the Sea of Japan coast of Russia and the largest decline near the Sea of Japan coast of north Honshu.

The complex Sea of Japan coast is important in modulating sea-effect precipitation. Downstream, the coastline and terrain of Honshu and Hokkaido are also complex. Central Honshu features the highest peaks and most sustained orography, reaching over 3,000 m above MSL in the Hida Mountains. The terrain of northern Honshu and western Hokkaido is less formidable, but includes numerous peaks over 1,000 m, with some reaching over 2,000 m. The densely populated coastal plains are especially vulnerable to sea-effect snow.

The climate of Japan is often described as monsoonal. Westerly to northerly flow predominates in winter, and southerly to southeasterly flow in summer, with associated variations in precipitation. This seasonal flow reversal reflects the continental-scale circulation changes of the Asian winter and summer monsoon systems, the former featuring the Siberian-Mongolian high over Asia and Aleutian low over the north Pacific. These circulation features result in frequent cold air outbreaks with westerly to northerly flow over the Sea of Japan. The resulting sea-effect precipitation systems share similarities with lake-effect precipitation systems of the Great Lakes, but tend to be deeper, are modulated by higher and more complicated topography, and more frequently feature transverse-mode snow bands....

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Gale Document Number: GALE|A624969877