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Drought is a period of abnormally dry weather with a serious shortage of water supply. Drought indices can be an advantageous indicator to assess drought for taking further response actions. However, drought indices based on ground meteorological measurements could not completely reveal the land use effects over a regional scale. On the other hand, the satellite-derived products provide consistent, spatial and temporal comparisons of global signatures for the regional-scale drought events. This research is to investigate the drought signatures over Mongolia by using satellite remote sensing imagery. The evapotranspiration (ET), potential evapotranspiration (PET) and two-band Enhanced Vegetation Index (EVI2) were extracted from MODIS data. Based on the standardized ratio of ET to PET (ET/PET) and EVI2, the Modified Drought Severity Index (MDSI) anomaly during the growing season from May–August for the years 2000–2013 was acquired. Fourteen-year summer monthly data for air temperature, precipitation and soil moisture content of in situ measurements from sixteen meteorological stations for four various land use areas were analyzed. We also calculated the percentage deviation of climatological variables at the sixteen stations to compare to the MDSI anomaly. Both comparisons of satellite-derived and observed anomalies and variations were analyzed by using the existing common statistical methods. The results demonstrated that the air temperature anomaly (T anomaly) and the precipitation anomaly (P anomaly) were negatively (correlation coefficient r = −0.66) and positively (r = 0.81) correlated with the MDSI anomaly, respectively. The MDSI anomaly distributions revealed that the wettest area occupied 57% of the study area in 2003, while the driest (drought) area occurred over 54% of the total area in 2007. The results also showed very similar variations between the MDSI and T anomalies. The highest (wettest) MDSI anomaly indicated the lowest T anomaly, such as in the year 2003, while the lowest (driest) MDSI anomaly had the highest T anomaly in 2007. By comparing the MDSI anomaly and soil moisture content at a 10-cm depth during the study period, it is found that their correlation coefficient is 0.74.
Munkhzul Dorjsuren; Yuei-An Liou; Chi-Han Cheng. Time Series MODIS and in Situ Data Analysis for Mongolia Drought. Remote Sensing 2016, 8, 509 .
AMA StyleMunkhzul Dorjsuren, Yuei-An Liou, Chi-Han Cheng. Time Series MODIS and in Situ Data Analysis for Mongolia Drought. Remote Sensing. 2016; 8 (6):509.
Chicago/Turabian StyleMunkhzul Dorjsuren; Yuei-An Liou; Chi-Han Cheng. 2016. "Time Series MODIS and in Situ Data Analysis for Mongolia Drought." Remote Sensing 8, no. 6: 509.
Drought index is a useful tool to assess and respond to drought. However, current drought indices could not fully reveal land use effects and they have limitations in applications. Besides, El Niño Southern Oscillation (ENSO), strongly influences the climate of Florida. Hence, understanding ENSO patterns on a regional scale and developing a new land use drought index suitable for Florida are critical in agriculture and water resources planning and management. This paper presents a 32 km high resolution land use adapted drought index, which relies on five types of land uses (lake, urban, forest, wetland, and agriculture) in Florida. The land uses were obtained from National Centers for Environmental Prediction (NCEP) North American Regional Reanalysis (NARR) data from 1979 to 2002. The results showed that Bowen ratio responded to land use and could be used as an indicator to monitor drought events. Then, an innovative regional land use drought index was developed from the normalized Bowen ratio, which could reflect not only the level of severity during drought events resulting from land use effects, but also La Niña driven drought impacts. The proposed new index may help scientists answer the critical questions about drought effect on various land uses and potential feedbacks of changes in land use and land cover to climate.
Chi-Han Cheng; Fidelia Nnadi; Yuei-An Liou. A Regional Land Use Drought Index for Florida. Remote Sensing 2015, 7, 17149 -17167.
AMA StyleChi-Han Cheng, Fidelia Nnadi, Yuei-An Liou. A Regional Land Use Drought Index for Florida. Remote Sensing. 2015; 7 (12):17149-17167.
Chicago/Turabian StyleChi-Han Cheng; Fidelia Nnadi; Yuei-An Liou. 2015. "A Regional Land Use Drought Index for Florida." Remote Sensing 7, no. 12: 17149-17167.