臺灣在秋季至次年春季時，大氣環流主要受亞洲大陸的反氣旋天氣系統影響。當盛行風受中央山脈地形阻擋，臺灣西半部呈現弱風和沉降現象，常導致空氣污染事件的發生。為探討臺灣行星邊界層（PBL）垂直結構發展特性，及其對大氣污染物傳輸和擴散過程的影響，本研究分析了2015年至2021年冬季板橋、花蓮和馬公三個測站每天早上和晚上八點探空觀測資料，並根據冬季常見天氣型態(1)東北季風、(2)高壓迴流和(3)弱綜觀天氣，分述探空資料垂直結構特性。 根據探空剖面資料的分析結果，臺灣東北季風的平均厚度約為1600m，板橋站由於地形原因冬季主要吹拂東風。花蓮站冬季早上近地表常有輻射逆溫的現象，並且在受東北季風影響的天氣時，風速明顯較強。馬公站受強烈北風影響，低層的位溫和比濕混合良好。在弱綜觀天氣時，板橋站和花蓮站有較顯著的海陸風，臺灣地區冬季的海風大約從早上10時至11時開始，並持續約8至9個小時。 比較聖嬰年、正常年和反聖嬰年時臺灣冬季的垂直探空剖面，在聖嬰年期間臺灣周邊地區的對流層低層有較強的南風，而在反聖嬰年期間臺灣近地層風向偏北，增強東風和北風。當冬季的東風增強時，臺灣背風側的沉降作用增強，更不利於大氣污染物的擴散。另外，北風的增強為臺灣帶來更多的境外污染物，導致較差的空氣品質。;From autumn to the following spring season, the atmospheric circulation of Taiwan is dominated by the Asian continental anticyclone system. Due to mountain blocking, western Taiwan, often experiences low wind speeds and strong subsidence, leading to serious PM2.5 problems. In addition, the planetary boundary layer (PBL) evolutions strongly affect air pollution dispersions. This study explored the characteristics of PBL through the analysis of daily observed sounding data located in northern Taiwan (Banqiao), eastern Taiwan (Hualien), and western Taiwan (Magong). The analysis was conducted according to different synoptic weather patterns including (1) prevailed by the northeasterly monsoonal flow; (2) under the influence of high-pressure peripheral circulation, and (3) weak synoptic weather conditions. According to the analysis results of the sounding profiles, the average thickness of the northeast monsoon is about 1600m in Taiwan. Banqiao is obviously affected by easterly winds in the northeast monsoon weather in winter. Hualien has obvious radiation inversion near the surface at 00 UTC in winter and the wind speed is significantly higher in the northeast monsoon weather. Due to the strong northerly wind, the potential temperature and specific humidity of the lower layer in Magong are mixed well. In the weak synoptic weather, Banqiao and Hualien have more obvious sea-land breeze circulation. The winter sea breeze in Taiwan starts from 10:00 to 11:00 in the morning and lasts for 8 to 9 hours. Comparing the sounding observation profiles of Taiwan during the winter of the El Niño year and the La Niña year. The results show that there is a strong southerly wind in the lower troposphere around Taiwan during the El Niño. During the La Niña, the wind direction of the near-surface layer is more northerly and the location of the continental cold high is more northerly, which makes the easterly and northerly winds stronger. When the easterly wind is stronger in the winter, the sedimentation effect on the lee side area of Taiwan is enhanced, which is unfavorable for the diffusion of atmospheric pollutants. The strengthening of the northerly wind will bring more foreign pollutants to Taiwan, resulting in poor average air quality.
