خلاصه ماشینی:
Geography and Environmental Hazards 24 (2018) Regional Drought Monitoring in Zayandeh-rud Basin Based on Time Series Variations of the SPI and Satellite-Based VCI Indices Marziehsadat Mirahsania1, Abdolrassoul SalmanMahinib, Alireza Soffianianc, Reza Moddares, d f Reza Jafarie, Jahangir Mohammadi a Ph. D.
The limitation of NDVI in drought monitoring is that NDVI cannot indicate the drought severity alone because of obvious time lag of NDVI response to precipitation and little effect of weighty rainfall events later in the growing season (plant seed production period) on NDVI (Ganesh, 2007).
This research aims to assess spatial distribution of VCI index through spatiotemporal monitoring of it using MODIS NDVI time series products in growth season over ZRB from April to October 2003 to 2014 (Mrahsani, Salman Mahini, Soffianian, Modarres, Jafari & Mohamadi, 2015).
Meteorological Drought Index The SPI is a station-based index which calculates the probability of precipitation in different time scales.
1. Metrological Drought Index (Monthly SPI) The long-term SPI (12 months) were calculated based on precipitation data collected from 26 meteorological stations around ZRB which had the same available beginning from January 2003 to December 2014.
Vegetation Condition Index (VCI) In the present study, the annual VCI time series maps were prepared in order to quantify drought from a long-term observation.
The drought was assessed through monitoring vegetation condition using VCI; subsequently, its correlation with SPI was obtained to be 0.
In addition, the area of normal category covered by VCI in the basin is coincident during the time period except 2008 and 2011 during which severe meteorological drought had been occurred.