Investigation of the trend of rainfall and vegetation changes in arid and semiarid regions (Case Study:Khorasan Razavi, Iran)

Climatic conditions of each region are the primary factors affecting the formation of settlements. Precipitation is one of the most important climatic parameters that contributing in changes in vegetation, especially in arid and semi-arid ecosystems. This study aimed to investigate the vegetation and precipitation changes using remote sensing data. The vegetation index images captured by X TERRA / MODIS between 2001 and 2013 with 8-day interval in May and June months were used as Vegetation Condition Index (VCI). Consequently, VCI as an index was calculated from the annual average of the two months. To evaluate precipitation data, we used data from 28 meteorological stations. The linear correlation between height and precipitation was used to obtain line equation at each station using DEM (Digital Elevation Model) maps to prepare precipitation maps for each year. The VCI images were normalized between zero and one and were grouped into four classes. The area of each class was then calculated in 2001 and 2013, followed by statistical analysis (i.e. chi-square test) . The results showed that both indices were significant at 95% with Sig = 0.000. The VCI index decreases when the precipitation is low, while it shows an increasing trend where the precipitation is medium to high, which in turn approves the vegetation dynamics.