| 摘要: | 全球暖化及氣候變遷是近年來國際上相當關注的議題，其中氣膠對大氣環境及地球系統能量收支有很大的影響，不同種類的氣膠其光學及輻射特性也有相當的差異，高吸收特性的氣膠會加熱大氣系統，如生質燃燒所產生的煙塵，低吸收特性的氣膠則冷卻大氣系統，如沙塵暴所造成的揚沙，因此，氣膠的吸收特性將是影響全球暖化及氣候變遷的重要因子之一。 本篇研究主要目的是結合衛星資料與地面觀測資料反演單次散射反照率，針對東南亞生質燃燒產生的煙塵與西非地區的沙塵探討不同氣膠種類的吸收及散射特性。主要的概念是使用一組同一地區時間相近的衛星影像，以乾淨大氣的地表反射特性作為參考基準，來反演受氣膠影響事件的單次散射反照率。研究結果顯示，當受氣膠影響事件的氣膠光學厚度高於0.5時，反演的誤可在3%以內，其中由生質燃燒產生的煙塵(泰國西北邊)單次散射反照率分別為0.88(藍光頻道)、0.84(紅光頻道)、0.84(近紅外光頻道)，吸收特性明顯。而在泰國東南邊的單次散射反照率為0.94、0.91、0.88，吸收特性相對較弱，從氣流軌跡的分析來看，吸收特性之強弱主要與氣膠的來源地區有關。對於沙塵(西非地區)反演的單次散射反照率則分別為0.91、0.95、0.94，具有較強的散射特性，但在夏季期間則具有較低值，由於該季節北風盛行，因此推估可能受到來自海洋地區強吸收氣膠的影響，如海鹽等。 由本篇研究結果與分析顯示不同地區氣膠吸收及散射特性上的差異，這些差異主要是由氣膠的來源地區與季節盛行風所造成的，而這些氣膠吸收特性的分析歸納對地球系統能量收支的計算上有很大的幫助。 Global warming and climate change are the most important issues of the Earth system in the recent years. Atmospheric aerosols can have an important effect on the energy budget of Earth system, and different aerosol type usually exhibits different distinct radiometric characteristic in absorption and scattering. The low absorption leads to top of atmosphere cooling, such as dust, while heating can take place inside the atmosphere for strong absorption, such as smoke. Thus the absorption of aerosol is an important factor of energy balance which can influence in global warming and climate change. The present study intents to investigate the absorption of smoke plumes from Southeastern Asia bio-mass burning and the dust particles in West Africa by retrieving the single scattering albedo(SSA) from the fusion of satellite data and ground-based data. The concept of retrieving SSA is based on matching the surface reflectivity in multiple view angle retrieved on clear day. The results showed that when the aerosol optical depth is more than 0.5 on hazy day, the error of retrieving SSA can be less than 3%. The mean values of SSA retrievals in the northwestern Thailand are 0.88(blue band), 0.84(red band), 0.84(NIR band) and 0.94 0.91 0.88 in the southeastern Thailand, respectively. According to trajectory analysis, smoke plumes from different region could exhibit distinct optical properties. As for the dust particles, the mean values of retrieved SSA in the western Africa are 0.91, 0.95, and 0.94 in the blue, red, and NIR spectral bands, respectively. However, the SSA values are much lower which may be polluted by the strong absorption of aerosols from ocean, such as sea salt. The results of this study imply that the absorptive property of aerosol mainly relates to the source region of aerosol types and the prevailing wind (monsoon), and the retrievals of absorptive property would be useful to the investigations regarding to the changes of Earth energy budget. |
