Friday, January 26, 2018

PyeongChang 2018 Olympic Weather Preview

With the Olympic Winter Games beginning on February 8, it seems like a good time to take a look at the climate of PyeongChang and the sorts of weather that we might expect in a couple of weeks.

PyeongChang is a county in the Gangwon province of South Korea.  On the broad scale, it lies on the eastern edge of Asia, east High Mountain Asia, including the Tibetan Plateau, and between the Yellow and East Seas.  The East Sea is known to many Americans and the Japanese as the Sea of Japan, but the Koreans as the East Sea, so for this post, I will stick with East Sea since they are the Olympic hosts.

Olympic venues are concentrated in the Gangneung Coastal Cluster, along the coast of the East Sea, and just inland in the PyeongChang Mountain cluster.  The topography of this region is a mumble jumble of small ranges and mountains.  In a broad sense, the Teabbek Mountains run from south-southeast to north-east, paralleling the coast, with some higher-elevation branches that extend southwestward.  The PyeongChang Mountain Cluster is near the crest of the Teabbek Mountains within one of these spurs.  Most venues in the mountain cluster are near the triangle, but the Jeongseon Alpine Center, site of the men's and women's downhill, super-G, and combined, are in the mountains about 15 km (10 miles) to the south.  The top starting altitude is for the men's downhill at 1370 meters (4495 feet), with finish altitudes for all races at the venue around 545 meters (1788 ft). The highest peak in the region is Seoraksan at 1707 meters (5,603 feet), about 50 km (33 miles) north of the mountain cluster.

Perhaps the closest (but imperfect) analog for the terrain of this region from past Olympic cities would be Lake Placid.  The photo below of the Yongpyong Alpine Center, site of the men's and women's giant slalom and slalom, reminds me a great deal of the high peaks region of the Adirondack Mountains.

The Gangneung Coastal Cluster includes hockey and curling centers, the ice arena for figure skating and ice dancing, and the speed skating ovals.  The PyeongChang Mountain Cluster includes the Olympic Stadium, biathalon and cross-country skiing center, ski jumping center, sliding center (skeleton, bobsled, luge), Phoenix snow park (snowboarding, freestyle skiing), Yongpyong alpine center (alpine skiing gs, slalom), and Jeongseon alpine center (alpine skiing dh, sg, combined).

The weather of PyeongChang and the Korean Peninsula during the Olympic period is strongly influenced by the Siberian high, characteristic of the Asian Winter Monsoon (monsoon means season).  The average sea-level pressure for February is shown below and illustrates the arm of the Siberian high that extends southeastward across eastern China and the Korean Peninsula.

Source: ESRL
The February climatological 1000 mb (near sea level) temperatures show that Korea, like the eastern seaboard of the United States, is relatively cold due to it's location downstream of a major continent.  Pyeongchang is located at a remarkably low latitude (37.3ºN) and altitude (500-1400 meters), but can host an Olympics because of the dominance of cold, continental air.  If you take a close look at the map, the Korean peninsula and nearby eastern China have the lowest average 1000-mb temperature at their latitude.  Amongst past Winter Olympic cities, only Nagano (36.6ºN), which similarly benefits from a location downstream of Asia, is further south.
Long-term climate averages for each cluster during the Olympic and Paralympic periods are provided below.  Unlike Japan, which benefits from being downstream of the East Sea, snowfall in the mountain cluster is relatively scant.  The 41.3 cm average for the 17-day Olympic period scales to a 30-day monthly mean of 72 cm (28 inches).  This would be somewhat higher than Lake Placid (19 inches).  

The coastal cluster being at lower elevation and east of the Teabbek Mountains might be expected to be drier than the mountain cluster, but it isn't.  It's actually slightly wetter, although due to the lower elevation, precipitation more frequently falls as rain.  The reason for this is the close proximity of the East Sea and the blocking effects of the Taebbek Mountains during periods of easterly flow, which drives the regions heaviest wintertime precipitation events.  An example is provided below.  The sea level pressure analysis (right) shows low-level easterly flow impinging on the Korean Peninsula.  The satellite imagery shows shallow sea-effect clouds streaming toward the Korean Peninsula with clouds and/or snowcover over the eastern peninsula, but clear skies and no snow cover further west.  

Source: Kim et al. (2016)
Such an easterly-flow precipitation event is one of the bigger major weather concerns for Olympics, although there are others. A summary of weather extremes at both clusters during the Olympic and Paralympic Periods is provided below.  

We were fortunate to host several meteorologists for the PyeongChang Olympic Games at the University of Utah approximately two years ago and have Byung-Gon Kim of the Gangneung-Wonju National University visit us while on sabbatical.  They appear to be very well prepared for the games.  Korea has an exceptional weather observing network of surface stations and radars, as well as many other platforms to help with specialized local prediction.  The best outcome for an Olympics is benign weather, but in the case of inclement weather, they will have great meteorological guidance to help with logistics and planning.  

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