薔蜜颱風(2008)襲台期間,環保署彰化測站於2008年9月27日中午13 時觀測到PM10濃度值高達459μg/m3。而附近測站如西屯站PM10 濃度為258μg /m3，與彰化測站之觀測值有一段差距。為探討其來源，本研究致力於windmodel 向後積分方法的研發。 本研究實驗包括彰化測站網格風場的分析、理想風場的測試以及真實風場的測試。於真實風場測試部分，設定模擬時間為9 月26 日12時至9 月27 日12 時。經過一連串向前積分及向後積分的測試、探討原因並修正方法，歸納出三個向後積分方法演進。向後積分法I 及向後積分方法II，主要進行搜尋範圍的大小(14 格、7 格、5 格)及時間敏感度測試(1 小時、10 分鐘)。而向後積分方法III 的實驗中，先將搜尋範圍設定於5 格時，進行時間步階為1 分鐘及30 秒的敏感度測試，及空間敏感度測試，即質點以向後積分所到達終點及終點之上、下、左、右各一格網格，共五點作為向前積分的起點，進行向前積分。 結果發現，於向後積分方法III 實驗中，以時間步階為30 秒時且搜尋範圍為5 格時，質點向後積分的軌跡路徑與向前積分的軌跡路徑有較好的一致性。故以相同的設定，進行彰化個案的探討，包空間敏感度測試以及鄰近測站向後及向前軌跡模擬，進一步推測彰化地區汙染物高值為局部地區的汙染。 ABSTRACT During the period of Typhoon Jangmi (2008) , EPA Zhanghua stationmeasured PM10 concentration up to 459μg/m3 at 13:00on September 27th2008. There is a difference between Zhanghua and Xitun where PM10concentration was 258μg/m3.In order to study the pollution source of Zhanghua, this research devotes to the development of the windmodelbackward caculation. The experiments conducted in this work including grid wind fieldanalysis at Zhanghua station, ideal wind field test and real wind field test.The model simulations were done with the real wind, started at 12:00 on 26 September and ended at 12:00 on 27 September. A series of tests, were conducted to locate sources of uncertainties in the model calculations. The backward integration method II, which focuses on spatial sensitivity tests (14 grid, 7grid, 5grid) and time sensitivity tests(1hr,10min). We have conducted tests with model setting of the search area of 5 grids and time-step of one minute；the backward integration method III with time sensitivity tests (1min,30sec)and spatial sensitivity tests . The backward integration method III shows most consistent results with the forward integration when a time-step step of 30 seconds, and the spatial search area is 5 grids were used. In the analysis of Zhanghua case, the results from the spatial sensitivity tests and run with other stations backward simulation, suggests that the sorce of high PM10 value of Zhanghua station is locally produced.
