| 摘要: | 本研究主要是利用WRF-CHEM ( Weather Research and Forecasting - Chemistry ) 模式模擬2010年3-4月七海計畫 (7SEAS, 7 South East Asian Studies)東沙實驗期間，生質燃燒煙流由中南半島長程傳輸至鹿林山，路徑上之化學以及光學特性變化。
鹿林山受到生質燃燒之不同事件日期間，依其不同天氣類型與軌跡路線將其分為兩類，第一種類型主要受到700 hPa等壓面上之西太平洋延伸高壓影響，第二種類型則主要以中南半島北方700 hPa槽線之影響為主，將兩種不同天氣類型時間之模式結果與衛星觀測相比，模擬結果顯示華北區域之氣膠光學厚度(AOD, Aerosol Optical Depth)與CO有低估，而生質燃燒煙流之分布則與觀測相近，因此模式結果在位於生質燃燒下游的鹿林山背景站有不錯的表現，一致性參數(IOA, Index Of Agreement)於CO、O3與PM10分別可達0.7、0.66與0.63，散射係數以及吸收係數則分別達到0.58與0.72，影響光學特性模擬好壞之差異主要來自質量濃度及局部環流之模擬準確性。單次散射返照率(SSA, Single Scattering Albedo)受山谷風影響，於模擬以及觀測結果上皆顯示晝高夜低之日變化。
為確認鹿林山事件日發生時，生質燃燒源區之影響以及瞭解煙流在軌跡上之光化學以及化學變化，本研究使用HYSPLIT軌跡模式(Draxler and Hess, 1998)推估鹿林山事件日發生前120小時煙流後推軌跡，結果發現煙流在通過源區一天至一天半後各氣膠成份以及氣體前驅物進入穩定狀態，直到抵達鹿林山皆無顯著變化，其中煙流內SSA之變化在進入生質燃燒源區後受到EC在PM10中之百分比增加而下降，而在離開源區後SSA之變化則與相對溼度十分類似。
;This study utilized the WRF-CHEM( Weather Research and Forecasting - Chemistry ) model to evaluate the optical and chemical properties of biomass burning plµme along long-range transport pathway from Indochina to Mt.Lulin during the 7-SEAS(7 South East Asian Studies) / Dongsha Experiment in March and April of 2010.
This study divided the weather type into two categories by different weather characteristics and trajectories for biomass plµme seriously influencing Mt. Lulin. The first type was mainly affected by extension of the Pacific high pressure at 700 hPa level. The second type was controlled by troµgh over northern Indochina at 700 hPa. The evaluation of WRF-CHEM performance by comparing satellite observation shows that simulated results of CO and AOD underestimated over North China, however the simulated distribution of biomass plµme is similar to observations. The simulated CO, O3 and PM10 have good performance as compared with Mt.Lulin. observations. In terms of IOA (Index Of Agreement), one of statistics in simulation, CO, O3 and PM10 were 0.7, 0.66 and 0.63, respectively. For scattering coeffiecient and absorption coefficient, the IOA of these optical factorswere 0.58 and 0.72, respectively. When simulation was over or underestimated in PM10, the scattering and absorption coefficients almost have the same situation. Due to valley wind, simulated and observed results have diurnal pattern.
For confirming the Mt.Lulin episodes affected by bimass burning and the variation of optical and chemical properties along the trajectories, We used the HYSPLIT model (Draxler and Hess, 1998) to simulate the 120-hour backward trajectory. After air mass passed the biomass burning source region, parts of the precursor gases converted to aerosols. Obviously, after about one and a half day the BB chemical compositions reached a near-stable state. The pollutants didn’t have significant change until arriving Mt. Lulin. The variational pattern of SSA was affected by EC portion in PM10 when air mass pass throµgh biomass burning source region. After passed source region, the trend of SSA in the BB plµme was similar to relative hµmidity. |
