2009年春季鹿林山背景站氣膠垂直分佈與光學特性分析

Aerosol Optical Properties Observed in 2009 Spring at Lulin Atmospheric Background Station, Taiwan

徐開炫(Kai-Husan Hsu)

指導教授 ： 林能暉

國立中央大學/地球科學學院/大氣物理研究所/碩士(2011年)

摘要

本研究旨在利用鹿林山空氣品質背景站( 23.469° N、120.874° E，2862 m MSL)之太陽輻射儀、積分式散光儀、微粒碳吸收光度計與環保署中央大學(海拔144公尺)之微脈衝光達進行氣膠垂直特性觀測，整合衛星、地面空氣品質和氣流後推軌跡等資料，探討鹿林山 2009 年春季(3-5月)氣膠光學特性與污染源之關連性。

氣膠光學厚度(τ500)平均值為 0.120 ± 0.105，3、4月τ500 高於 5 月，與 CO 及 PM10 濃度變化趨勢相同。Ångström exponent440-870nm 平均為 1.170 ± 0.374，且3、4月高於 5 月，顯示 3 、 4 月氣膠粒徑較小， 5 月氣膠粒徑大。地表單次散射反照率日平均值隨波長增加而遞減，此為混合型氣膠的特徵，且 3 、 4 月較小，顯示當時氣膠對於太陽輻射具有較強的吸收作用， 5 月地表氣膠則有較強之散射作用。垂直氣柱不對稱因子(g)日平均值隨波長增加而緩慢遞減，此種特徵偏向混合氣膠的狀態特徵。垂直消光係數剖面平均結果顯示春季氣膠分佈呈現兩層結構之特徵，下層高度為 0.3-2 公里，氣流來源以蒙古、中國北部及日韓地區為主，上層高度為 2.3-5 公里，氣流來源為中南半島與中國南部。

3/16-3/23生質燃燒事件期間，氣膠中OC 、 EC 、 K+ 、 Ca2+ 、 NO3- 質量濃度出現明顯高值且具有相同變化趨勢。由日變化趨勢可知夜間鹿林山背景站單次散射反照率普遍較低，且於每日 12:00 UTC 前後發生較明顯之數值變化。此外，本研究針對生質燃燒與春季背景事件進行比較，春季背景單次散射反照率隨波長下降幅度小， g 隨波長先降後升，垂直分佈介於0.3至1.7公里間；生質燃燒事件單次散射反照率與 g 值隨波長增加而遞減，高度分佈於1.7至4公里。

春季鹿林山背景站之氣膠具有生質燃燒及沙塵特徵，5 月氣流來自中國、韓國等地，Ångström exponent440-870nm 、單次散射反照率與?g 值呈現粒徑大、散射強之沙塵特性。3、4月氣流經過中南半島，氣膠光學厚度高於 5月，氣膠光學特性數值顯現出粒徑小、吸收強之生質燃燒特徵，且於明顯生質燃燒事件期間(3/16 - 3/23)，鹿林山背景站與中央大學上空2 - 4公里之氣膠性質相似性高。

關鍵字

氣膠 ； 光達

並列摘要

The purpose of this study is to characterize the aerosol optical properties measured by using Sun-Photometer, Nephelometer and Particle Soot Absorption Photometer at Lulin Atmospheric Background Station (LABS, 2,868 m; 23.47°N, 120.87°E) during spring (Mar-May) 2009. In combination with the use of micro-pulse lidar (MPL) in Chung-Li, satellite, ground-level particle mass concentrations and backward trajectory analysis, a comprehensive study of the vertical profile of aerosol optical properties and the source-receptor relationship was achieved.

The mean aerosol optical depths (?500) was 0.120 ± 0.105, and much higher in March and April. The variation of CO and PM10 was consistent ?500. The averaged Ångström exponent????????nm was 1.170 ±0.374, and March and April also higher, indicating the particle size was larger in May.The single scattering albedo (SSA, ?) at surface decreased gently with increasing wavelength, revealing the characteristics of mixing aerosols. Lower ?550nm in March and April showed that aerosol had more absorption capability. The asymmetry factor (g) decreased with increasing wavelength, also indicating the characteristics of mixing aerosols. Extinction coefficients derived from MPL and CALIPSO(Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations) showed a two-layer structure (0.3-2 km and 2.5-5 km). Backward trajectory analyses of upper layer(2.5-5 km) showed that these air masses were mainly from the Indo-China peninsula. Low-level air masses were mainly from Mongolia and northern China.

During the event of 3/16-3/23, variation of OC、EC、K+、Ca2+ and NO3- had similar trends and higher values. There was commonly low ????nm at nighttime, and the value varied significantly at about 12:00 UTC. In addition, the ??decreased gently with increasing wavelength during springtime background situation. Meanwhile, the g first decreased and then increased with increasing wavelength. The vertical profiles of aerosol extinction showed higher values between 0.3 and 1.7 km in springtime normal situation. Influence of biomass burning was the most significant between March 18 and 23, as indicated by a high average AOD of 0.45. The ? and g decreased with increasing wavelength. The vertical profiles of aerosol extinction showed higher values between 1.7 and 4 km during biomass burning event.

並列關鍵字

aerosol ； Lidar

參考文獻

劉承珏，2009：以光達觀測分析台北之邊界層與氣膠特性。國立台灣大學大氣科學研究所碩士論文，台北。

地區氣膠光學垂直特性分析。國立中央大學大氣物理研究所碩士

張佑嘉，2011：中南半島近污染源生質燃燒氣膠特性及其傳輸演化

林家慶，2007：鹿林山空氣品質背景監測站之背景值分析。國立中央大學大氣物理研究碩士論文，中壢。

徐睿鴻，2007：鹿林山與中壢氣膠光學特性之監測與比較。國立中央大學，大氣物理研究所碩士論文，中壢。