Assessing drought severity from Multi-Temporal GIMMSNDVI and rainfall interactions

Abstract

Drought being recurring climatic events is a major cause of agricultural, economic and environmental damage which often hit Ethiopia, bringing significant water shortages, economic losses and adverse social consequences. At present, regions of the countries have limited institutional and technical capacity to prepare for drought and to mitigate its impacts. This paper first investigated the historical climate change pattern and droughts in the region from 15 day Advanced Very High Resolution Radiometer Global Inventory Modelling and mapping Studies-Normalized vegetation Index (AVHRR GIMMS-NDVI) and climate variables. The Drought patter in the area is mapped using drought-related indices obtained from different pixel-resolution and optical characteristics NDVI and AVHRR data. The period 1981 to 2006 is selected with improved information on clear sky radiances and cloud cover fraction (CCF) less than 10%.The relation between vegetation (NDVI reflectance) and precipitation depends on season of the year and time of the day. A strong positive Rainfall and NDVI correlation is found in the spring and summer seasons. The NDVI-Rainfall relationships are generally negative in the autumn, winter and spring seasons than May of high positive correlation. In the years with high rainfall amount, the prediction of NDVI patterns by rainfall is larger and the R is higher. On the other hand, in the years with low rainfall value, Celsius temperature factor plays an important role, and the value of R2 is lower. The highest maximum NDVI occurred in 2003 following the year's wet season, and the second highest NDVI has occurred in 1999 following the wet year of 1998 and lowest maximum NDVI is observed in the year 1997.