乾旱及沙漠化與區域社會和經濟因素有著密切的關係。氣象乾旱的各種特性對農業產量造成影響，如降水短缺、實際和潛在蒸發散量間的差異、土壤水分缺乏及其他土壤和植物之生理因素。本文將探討利用遙測技術監測蒙古之乾旱狀況。本研究應用MODIS/Terra 影像計算溫度植被乾旱指數(TVDI)，並應用該指標監測蒙古2002-2009 年的夏季乾旱變化情形。EVI-Ts 特徵空間(feature space)是由地表溫度(Ts)和增揚植被指數(EVI)所構成，並進一步獲得TVDI，以表示蒙古地區之乾旱情形。研究結果將TVDI乾旱條件分為五個等級：濕潤(0-0.2)；半濕潤地區(0.2-0.4)；正常(0.4-0.6)，中度乾旱(0.6-0.8)及嚴重乾旱(0.8-1.0)。並收集地面測站之氣象資料與土壤濕度資料與TVDI 進行比對。Drought and desertification are closely related with social and economic factors. Various characteristics of meteorological drought cause impacts on agricultural yields, such as precipitation shortages, differencesbetween actual and potential evapotranspiration, soil water deficits, and other physiologic factors of the soil and plants. In this paper, remote sensing is utilized to monitor drought condition over Mongolia. In this study, the Temperature Vegetation Dryness Index (TVDI) which is derived from MODIS/Terra data was applied to monitor thedrought over Mongolia in the summer season from 2002 to 2009. Based on the EVI-Ts feature space, which was constructed by Land Surface Temperature (Ts) and Enhanced Vegetation Index (EVI) extracted from the MODIS satellite data, the TVDI was calculated to characterize the drought condition. According to the classification standard of TVDI used in the literature, the drought condition was divided into five grades: humid (0-0.2), sub-humid (0.2-0.4), normal (0.4-0.6), moderate drought (0.6-0.8), and severe drought (0.8-1.0). The meteorological data and soil moisture data were collected to compare with TVDI.
