落山風影響下的恆春機場風場分析

Abstract

位於台灣最南端的恆春機場，目前的民航設施在2004年啟用後，因深受落山風之影響，機場關閉頻仍，實際使用率不高。為了理解恆春機場為何開航後，受到風的影響如此之大，本研究以民航局恆春機場所紀錄的風場資料，佐以超過半世紀之久的中央氣象局恆春氣象站數據，分析該地區的風場特徵，得知目前恆春機場的跑道，與當地落山風季節之盛行風風向相差約90°，是種極端明顯的強烈側風，對於起降之飛機來說有極高的風險。而除了氣候平均場分析外，本研究也以較長時間的風場年際變化，發現赤道太平洋發生聖嬰事件時，恆春落山風季節的大風次數較少，而反聖嬰年時則較多。這樣的情況，與中到東太平洋的海平面溫度，會在菲律賓海處激發出的羅士比波反應（Rossby wave response）環流結構有關，而此環流距平會進而影響東北季風之強弱，對恆春落山風季節的大風事件頻率有所影響，值得此機場未來營運與規劃時參考。

The Heng-chung airport, opened in 2004, is the southernmost airport in Taiwan. This airport closes frequently due to the weather condition, especially the influence from its prevailing winds, the ”downslope winds” (Luo-shan wind). Using observed wind data from the Heng-chung airport and the Central Weather Bureau Heng-chung weather station, this study found significant cross winds during the famous ”downslope wind” season in the Heng-chung airport. Analysis of long-term climate data revealed that the interannual variability of the strong-wind occurrence is related to the El Nino/La Nina events over the equatorial eastern Pacific Ocean. More/less frequent strong-wind occurrences in the ”downslope wind” season were identified during the La Nina/El Nino events due to the Rossby wave response over the Philippine Sea. This results in a strong/weak northeasterly flow near Taiwan and have the influence on the wind patterns in the Heng-chung airport. The result obtained here is important for the operation and planning of the Heng-chung airport in the future.