56 年間 韓半島 降水 및 風速의 强度 變化

Abstract

Natural disasters occurring in Korea mostly has something to do with severe weathers like heavy rain in summer, typhoon, rainy spell in summer and heavy snowfall in winter. Entering the 21st century, the damages caused by heavy rainfall and strong wind are remarkably becoming larger and larger. This paper studied the features of the changes in intensity of severe weather using the The annual extreme value of daily precipitation and maximum instantaneous wind speed from 1951 to 2006. As a result, there are some increases by 230mm over the last 56 years in daily precipitation extreme value and by 15m/s in maximum instantaneous wind speed. The analysis was conducted in seven different positions to make away with possible impacts from changes in the number of observation position. The result was that while daily precipitation in all the positions showed somewhat to be risen, the extreme value of maximum instantaneous wind speed in most sites showed a downward tendency. For more detailed study, the daily precipitation data was analyzed through the frequency and contribution assessment for certain class interval Karl and Knight used. According to the results, while the rate of days with low precipitation out of the whole rainy days showed a downward tendency in all the regions, the rates of days with high precipitation was on the rise. In addition, precipitation intensity the total precipitation divided by the number of days with precipitation gives turned out to be increasingly upward. The change trend was researched of the extreme value of maximum wind speed for the seven positions, days with maximum wind speed above 14m/s, the reference point of the strong-wind advisory and days with maximum wind speed above 21m/s, the standard point of the strong-wind warning. Despite most regions showing a downward trend, the extreme value of maximum wind speed decreased by 10m/s and the extreme value of maximum instantaneous wind speed increased by 6m/s according to the change trend only in the seven points. But the analysis results in the fifteen points decreased by 2m/s, 6m/s in 56 years. This result represents that wind speed intensity decreased unlike daily precipitation in the Korea Peninsula. That is because friction increase by urbanization. Actually, the increase of Korea's severe weather intensity shown in daily precipitation and maximum instantaneous wind speed has a close relationship with changes in typhoon's strength that hit the Korean territory. Typhoon made happen 23 times, 41% out of the daily precipitation extreme value and 27 times, 48% out of the maximum instantaneous wind speed extreme value over the last 56 years. Beside other factors, daily precipitation extreme values and maximum instantaneous wind speed extreme values by each year triggered only by typhoon showed a significantly upward trend. While the number of typhoon that had made any damages in Korea wasn't risen, its strength kept its upward tendency. Indeed, the change trend of daily minimum air pressure extreme value observed during the typhoon attack showed the value keeping its downward trend on and on. Therefore, the increase of typhoon intensity can be seen as an important factor of increasing daily precipitation and maximum instantaneous wind speed in Korea. As for the warning trend in Korea, the change trend of maximum and minimum temperature at the seven points showed that while maximum temperature in four regions decreased by around one degree, minimum temperature rose in all the sites by around one to three degrees. In addition, water temperature observed in four points of Buoy around Korean sea area increased by one to two degrees. And from 2001 to 2006, sea surface temperature of Korea's neighboring waters in October showed an increasing curve, as well. From these results, air and sea surface temperature increases triggered by warming trend in Korea are expected to make lethal changes threatening to human survival like increasing severe weathers, changes in precipitation pattern, rise in sea-level, and strengthening typhoon intensity. Finally, daily precipitation and maximum instantaneous wind speed were studied in Jeju-do which is affected relatively less than the continent due to its regional characteristics. Its extreme value of daily precipitation has increased by 30mm, extreme value of maximum instantaneous wind speed by 10m/s, and maximum wind speed by 10.5m/s over 57 years. But more detailed change trend by each regional part showed that while the extreme value of daily precipitation increased in most areas, maximum instantaneous wind speed and maximum wind speed showed a upward trend only in Gosan and Seongsan. Gosan and Seongsan are naturally notorious for relatively stronger wind. But this case might especially result from regional features of Gosan exposed to north-west types of wind coming and Seongsan exposed to south-east types of wind coming from the ocean nearby. Given all these results, the warming trend in Korea is under way, and the intensity of severe weathers is increasing, accordingly. In particular, daily precipitation increases triggered by typhoon intensity is a nationwide trend of Korea. And while urbanism is helping decrease the rates of days with strong wind speed and averaged wind speed, instantaneous wind speed in the case of severe weathers is becoming stronger and stronger. According to the IPCC report, if human activities dependent on fossil fuel are kept as it is now, averaged temperature of this planet would be increased by 6.4 degrees at most in the late 21th century. If things occur as this report says, Korea's severe weather intensity and frequency in the future would be expected to get higher than now.