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.
Majid Danesh; Hosseinali Bahrami; Seyyed Kazem Alavipanah; Aliakbar Nowruzi
Volume 17, Issue 67 , October 2008, , Pages 26-34
Abstract
Soil texture and lime can be considered as amongst the most important soil characteristics, which are considered in many agricultural and environmental projects. Today, with the scientific progress and the advent of remote sensing technology, the possibility of exploiting this technology in soil science ...
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Soil texture and lime can be considered as amongst the most important soil characteristics, which are considered in many agricultural and environmental projects. Today, with the scientific progress and the advent of remote sensing technology, the possibility of exploiting this technology in soil science has also been provided. In this study, for the analysis of soil texture and lime in the Pol Dokhtar area, the four-spectral data for September 7, 2007 prepared by IRS-P6 satellite with LISS III sensors were used. Geometric corrections and processes including UNC, SLED, NDVI, PCA, were performed on the main image. Finally, using randomized sampling method and based on PMU, FCC image of the region, 95 points were selected and samples were taken from two depths of 0-5 and 20-5 cm. Finally, using multiple regression, it was found that the lime and clay of samples at the first depth had a significant relationship with the near infrared band with modified R2 =0.73, and in the green band it was 0.72, and also at the second depth, with a red band of 0.54 and a green band of 0.48, of which all relationships were statistically significant at 1% statistical level. Consequently it was found that clay and lime have a significant effect on the spectral reflection from the soil surface in the region, and it is possible to study them in the region using satellite data and auxiliary data (incidental information).
