沙塵暴長距離輸送至台灣之數值模擬研究

A Study of Numerical Simulation of Dust Storm and its Long-range Transport to Taiwan

蕭玲鳳(Ling-Feng Hsiao) ； 王自發(Zi-fa Wang) ； 劉廣英(Koung-Ying Liu)

《華岡理科學報》 18期 (2001/05) Pp. 1-20

摘要

根據近年來環保署觀測資料顯示，沙塵長程輸送到臺灣造成空氣品質惡化的日數有增加趨勢，因而形成另一種污染現象。本文採用最新設計完成的沙塵三維歐拉輸送模式，模擬2000年3月大陸地區沙塵的起沙以及輸送過程。該模式使用適合東亞地區起沙機制新模型，所選取的三個指標（天氣系統、地面濕度以及摩擦速度）可使沙塵事件漏報與虛報的次數達到最小。模擬結果以及觀測資料均清楚顯示春季大陸沙塵輸送對台灣地區空氣品質之影響。大陸北部地區產生的沙塵主要輸送路徑有兩條，即向東輸送和向東南輸送。沙塵只有沿第二條輸送路徑並且強度夠大才會對臺灣的空氣品質造成重大影響。由此個案模擬結果顯示，模式對沙塵的到達時間具有較好的預報能力，但是對於濃度值的預報，仍存在一定的偏差，這主要是因為起沙機制所計算沙塵源強度依然具有較大的不確定性。

關鍵字

沙塵 ； 輸送模式 ； 空氣品質 ； 起沙機制 ； 預報

並列摘要

Evidences of EPA’s observations show that more and more dust sands occurred in Taiwan due to the long-range transport and result in air quality decrease. A long-range transport model developed by Wang et. Al. (2000) was used to simulate the blowing-up and transport of yellow sand in March 2000 over East Asia. A new deflation module was adopted in the LRT model to make the error ratio of false declarations and missed declaration minimized with the three predictors: the friction velocity, the surface humidity and the dominant weather system. Observation and simulation results clearly indicate the effects of the long-range transport on the air quality in Taiwan. There are two mainly transport paths, i.e., eastward and southeastward. Only with the second path and having enough emission intensity may the dust sands be transported to Taiwan and affects the air quality over there. The model can reasonably predict the arriving-time of yellow sand to Taiwan. But, due to the uncertainties in estimating the emission intensity cause more errors in prediction of concentration.

並列關鍵字

Yellow sand ； transport model ； air quality ； deflation module ； prediction