Rangeland Drought Monitoring Using MODIS Satellite Images in West of Iran for 2007-2009

Drought monitoring has a key role in drought management. The meteorological drought monitoring in regions without enough data is always influenced by the Lack of meteorological data and deficiency in statistical data. On the other hand rainfall data is not a good indicator for rangeland drought evaluation, because of its temporal and regional distribution. In this research, variation of rangeland drought is investigated by MODIS data with 250m spatial resolution that collected in the duration of 2007-2009 fromwest part of Iran. Due to effects of drought on the quality and quantity of vegetation cover, NDVI (Normalized Difference Vegetation Index) was used as important indicators of rangeland drought. NDVI is used as vegetation index of growth season in rangelands and grasslands. So, Standard Precipitation Index (SPI) was calculated as meteorological drought index to monitor drought impact on the variation of vegetation cover. Thus, annual analysis was done to show the general trend of drought in the study area. Then the monthly analysis also applied to obtain the correlation (R) between NDVI and cumulative precipitation, SPI in different time lags. As final result, the best correlation accrued in 6 months lag and the most growth of correlations happened between 1 and 2 months. This research also presents the daily MODIS data is useful for drought study in the area with no reliable data.