| 摘要: | 本研究為利用太陽輻射儀(CIMELs) 與多重濾鏡旋轉輻射儀(MFRSR) 於2009年9月至2010年8月在東沙空氣品質背景測站(5 m；20.70°N，116.73°E)之觀測，探討氣膠光學特性。季節分析顯示氣膠光學厚度(AOD500nm)和Angstrom exponent 高值主要發生在春季(3-5月)，推論受長程傳輸的生質燃燒氣膠影響為主。特別地，二月Angstrom exponent 平均已達1.6，配合MODIS衛星觀測火點分布資料，可知二月東南亞已有明顯生質燃燒情形，此影響之時間點與觀測結果吻合。 進一步分析氣膠單次散射反照率(Single Scattering Albedo, SSA)、不對稱性因子(Asymmetry Factor)及細微粒氣膠比例(Fine Mode Fraction, FMF)，結果顯示東沙背景站以細粒氣膠為大多數，且具有生質燃燒/城市污染來源氣膠特性。HYSPLIT 氣流後推軌跡分析顯示近地面(1000hPa)空氣塊來源為中國東北、日韓及菲律賓；中高層(700hPa)受盛行西風主要來自中南半島，少部分來自中國及菲律賓。整年輻射驅動力平均為-45 Wm-2，受沙塵與生質燃燒/城市污染影響平均分別為-105Wm-2 與-66Wm-2。除此之外， 本研究期間發生二十年來影響台灣最大之沙塵事件(2010/3/21-23)，其影響範圍遠達南中國海，此期間觀測Angstrom exponent440-870nm 和FMF 分別為0.4-0.9和0.3-0.5，受沙塵暴影響具有粗粒徑顆粒氣膠特徵。本研究雖僅提出一年之觀測資料進行分析，然而，此研究為第一次於南中國海的氣膠光學特性研究，強調其季節變化特性，以及多元氣膠來源(包括人為、生質燃燒和沙塵)，可做為區域氣候變遷的先期研究。 Simultaneous measurements of a multi-filter rotating shadowband radiometer (MFRSR) and a Cimel’s sunphotometer (CIMELs) were conducted at Dongsha Island (5 m AMSL; 20.70°N, 116.73°E) in the South China Sea from September 2009 to August 2010. This is the first research to study the aerosol optical properties over the South China Sea, focusing on seasonal variation and source-receptor relationships. The values of AOD500nm and Angstrom exponent were relatively high in spring (March-May), suggesting the influence of fine particles released from biomass burning emissions in the IndoChina Peninsula. Particularly, Monthly mean Angstrom exponent value in February had been for 1.6, coordinate with the MODIS fire detection data and images showed that a large number of biomass burning events were occurring in the Southeast Asia between February, and may coinciding with the results of our observations. Results of the single scattering albedo (SSA), Asymmetry Factor, and the fine mode fraction (FMF) analyses showed that fine particles dominated at Dongsha, carrying aerosol properties of biomass burning and urban pollution origins. Backward trajectory analysis indicated that the surface level (1000hPa) air masses were mainly from Northeast China, Japan, Korea and Philippine, On the other hand, due to the influence of prevailing westerlies, the upper level (700hPa) air masses were mainly from the IndoChina Peninsula. A massive dust storm event was observed at Dongsha in 2010/3/21-23. During this dust storm event, the Angstrom exponent440-870nm and FMF were 0.4-0.9 and 0.3-0.5, respectively, indicating the characteristics of coarse dust particles. |
