The assessment of relationship between MODIS vegetation indices and drought on northern rangelands of Golestan province

Analysis of drought and factors affecting it using remote sensing data has a high potential to improve scientific knowledge about the properties of drought and the effects of this phenomenon on vegetation. The present study was aimed to investigate the relationship between satellite indices and the SPI index in northern rangeland of Golestan province. For this purpose, SPI index in one, three, and six month- moving averages was calculated and then zoning maps were prepared using kriging. Then, using MODIS images and the corrections, required for this type of sensor, made on the images, a vegetation map was prepared using the indices of NDVI, SAVI and VCI. In order to synchronize the climate data with satellite images, a 9 -year-old common time base was selected. Finally, in order to investigate the relationship between vegetation indices with the SPI indices correlation coefficient and linear regression were used. The results indicated a good correlation between satellite indices and SPI indices in the peak months of vegetation growth. In addition, correlation between vegetation cover indices and three and six-month moving average in non-growing season, and with a one-month moving average of SPI in growing season was higher.