Characteristics of Jeju Wind
Jeju is an island located in the east of Eurasia. It has both continental and maritime climate, which show considerable seasonal variation. Jeju winter has wide daily temperature ranges affected by northwest monsoon and the resulting continental climate. In summer, Jeju has concentrated rainfalls due to the hot and humid north Pacific air mass.
The annual average temperatures, according to the recent record, is 16.2oC for Seogwipo-si and 15.5oC for Jeju-si and high mountain areas. The annual temperature ranges of Jeju are the lowest in Korea. The presence of Mt.Halla creates temperature gap between Jeju-si and Seogwipo-si. In summer, Seogwipo-si temperature is 0.5~1.5oC lower than Jeju-si as southwesterly wind climbs Mt.Halla before heading to Jeju-si. On the other hand, in winter, Seogwipo-si temperature is higher than Jeju-si.
Starting from June, average temperatures of the entire Jeju record higher than 20oC. From September, they fall 4~5oC, which continue until January. The temperatures then start to rise in February by 0.4~0.8oC and keep rising 2~3oC in March, 4~5oC each year from April to August.
In Jeju, there are approximately 360 parasitic volcanoes, called oreum, scattered around Mt.Halla. With many relatively high oreums of 300m to 700m above sea level, the eastern part of Jeju has localized gale zones. During daytime, Jeju mountains facilitate circulation of sea and land breeze by combining sea and land breeze while mountains cause land breeze to occur in most of the island at night.
Jeju is known for its strong and frequent wind force. That is because its winter has bigger atmospheric pressure difference between sea and land than the summer. The average wind speed of Jeju, as of 2003, is 3.1m/s. The highest wind speed is 6.9m/s in Sanseo area around high mountains.
Strong wind force is mostly seen in northwest coast where winter monsoon has great influence, while southeast coast area has relatively weak wind. Wind blows hard in spring. Before rain band reaches Jeju, Jeju is under the influence of winter monsoon.
The wind speed of high mountain area, as of 2003, peaks in the mid January with 9.7m/sec. It is the lowest in mid June and late July with 4.7m/sec.
A small vessel cannot stand speed over 8m/sec. Wind of that magnitude blows for more than ten days each month from October to April of the next year.
If ships stop over in Jeju through the East China Sea or are stranded nearby, the winter northwest wind is mostly to blame. But such strong wind is rare from May to September. For example, September has only six such as days on average.
The wind direction varies dramatically from season to season. From January to March, wind blows mostly from between north and northwest to the Straits of Jeju. Among them, north-northwest wind is the most frequent. From April to June, wind does not blow from one particular direction. From July to October, wind from between north-northeast and south is dominant. Wind blows from between north-northeast and northwest in November and between north and west-northwest in December.
Spring gust, though it is not strong, greatly affects the residents depending on sea for their livelihood. In March(February in the Chinese calendar), temperate low-pressure zone often moves eastward from its origin of the Yangtze River. It becomes stronger when combined with subtropical jet streams.
Typhoon and storm arrive at the Southern edge of Jeju between July and September. Typhoon is developed in Taiwan and East Philippine and moves north before being separated and going in several directions of northeast at Jeju.
Before modern times, there were cases of drift to Jeju among many other areas of East China Sea before modern times. Most of them were brought from South China and Okinawa by typhoon and storm of July and September. Hamel, too, wound up in Jeju primarily because of typhoon.
Relying on the sea for their livelihood, Jeju people had to overcome the challenge of wind. That is why Jeju people designated the period from Jul.1st and 15th(in Chinese calendar) as one for worshiping god of wind called Youngdeung halmang.
During that time, people stop working at sea and wish safety at sea and good fish catch.
