Ali Akbar Damavandi; Mohammad Rahimi; Mohammad Reza Yazdani; Ali Akbar Noroozi
Abstract
Abstract
Drought is a natural phenomenon that occurs in almost all climates of the world. The effects of this creeping and gentle phenomenon are higher in arid and semi-arid regions due to their less annual rainfall. In the present research, in order to monitor the location of drought, time series NDVI ...
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Abstract
Drought is a natural phenomenon that occurs in almost all climates of the world. The effects of this creeping and gentle phenomenon are higher in arid and semi-arid regions due to their less annual rainfall. In the present research, in order to monitor the location of drought, time series NDVI ((Normalized Difference Vegetation Index)) and LST (land surface temperature) of the Terra satellite’s MODIS (Moderate Resolution Imaging Spectroradiometer) sensor were used during the growing seasons (March, 21 to September, 21) of the years 2000 to 2014 in Markazi province. For this purpose, the VCI (Vegetation Condition Index) and TCI (Temperature Condition Index) indices were created on a monthly basis based on the NDVI and LST 15-year time series, and the VHI (Vegetation Health Index) index was extracted based on the combination of the two indices. As a result, drought severity maps based on the VHI index were extracted in five categories: 1- Very severe 2- Severe 3- Moderate 4- Mild 5- no drought, and variations of these classes were investigated in VHI time series. A review of time series resulted from VCI and TCI showed that there was a meaningful relationship between NDVI and LST variations. According to the results of drought severity classification maps, VHI index had the highest drought intensity in the years of 2000 and 2001 and the years of 2004 and 2007 had the lowest drought severity. Also, the highest and the lowest drought severity were observed in May and September, respectively. The highest percentage of the areas of drought classes belonged to drought-free (56%), mild (19%), moderate (15%), severe (8%) and very severe (2%). Comparing the results of this research and the report of the Meteorological Organization shows the high precision of the method of using the VHI remote sensing index in agricultural drought monitoring. The result is that, remote sensing indicators of drought monitoring (such as VCI, TCI and VHI) can greatly help decision-makers and planners in monitoring agricultural drought by eliminating the weaknesses of point-based approaches.
