近年來，對人體健康造成嚴重威脅的懸浮微粒(Particulate matter，簡稱PM)，已在全球成了相當重要的議題。然而，我們對於其在氣候統計上的年週期變化以及年際變化依舊沒有充分的了解與估量。
在本研究中，我們發現東亞季風環流的垂直運動能影響邊界層高度的發展，進而調節臺灣PM濃度的年週期變化。藉由了解PM長期氣候的年週期變化，我們可以定義臺灣的污染季起於每年的10月並延續到隔年的4月。接著，我們進一步劃分污染季生命週期的5個相位，分別為：肇始(PM10 肇始日PM10 onset date，簡稱PMOD)、活躍(11月至隔年1月November to January，簡稱NDJ)、中斷(農曆新年期間，約1月底至2月初)、 復甦(2月至4月February to April，簡稱FMA)以及衰退(PM10 衰退日PM10 retreat date，簡稱PMRD)，此結果正好與已知的東亞夏季季風生命週期相似。
有了PM污染季生命週期的明確定義後，我們得以更深入地針對其年際變化進行探討。結果顯示，在聖嬰時期(El Niño)的PM肇始日(PMODs)與衰退日(PMRDs)都較反聖嬰時期(La Niña)提早，尤其肇始日，在兩種不同的聖嬰-南方震盪(El Niño-Southern Oscillation，簡稱ENSO)事件下，有相當顯著的20天差異。在污染季的活躍期，不同的ENSO情境並未對PM濃度變化造成明顯的影響，反而是在復甦期有著顯著的差異。總結來說，氣候統計上PM污染季在深冬時期受到年循環的季節變化所主導，但在季節轉換時期的10月以及3月，ENSO則對PM濃度變化有著相當顯著的作用。此外，我們也測試了準兩年振盪(Quasi-Biennial Oscillation；QBO)是否同樣對PMOD/PMRD造成影響，結果顯示QBO與PMOD/PMRD皆未有顯著的關係。

Particulate matter (PM), which causes severe problems in human health, has become an important global issue in recent years. However, the climatology of annual variations and the interannual variations in PM concentrations have still not been fully evaluated.
In our research, we found that the vertical motion of the East Asian monsoon system can affect the development of the boundary layer height and subsequently regulate the annual variation in PM over Taiwan. By climatologically understanding the annual variation in PM, the PM pollution season in Taiwan, from October to the following April, can be delineated. Then, we further defined five phases of the PM pollution lifecycle that are similar to the well-defined East Asian summer monsoon lifecycle: onset (PM10 onset date, PMOD), active (November to January, NDJ), break (between the end of January and early February), revival (February to April, FMA) and retreat (PM10 retreat date, PMRD).
After the PM pollution lifecycle was precisely defined, the interannual variation in the PM concentration became clearer. The starting (PMODs) and ending (PMRDs) dates of the PM pollution seasons are earlier during El Niño episodes than during La Niña episodes; in particular, there is a significant 20-day difference between their starting dates. For the active phase (NDJ), climatological PM pollution development does not show distinct features under the two different El Niño-Southern Oscillation (ENSO) episodes. On the other hand, the influence of the El Niño and La Niña forcings on PM pollution during the revival phase (FMA) is significant. In summary, the climatology of PM pollution in winter is dominated by the annual seasonal cycle, but during the seasonal transition periods, October and March are significantly modulated by ENSO. In addition, our study examined the relationship between PMOD/PMRD and quasi-biennial oscillation (QBO). The results show that the QBO has no significant influence on either the PMOD or the PMRD.

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