Using Drought Indices to Model the Statistical Relationships Between Meteorological and Agricultural Drought in Raya and Its Environs, Northern Ethiopia

Abstract

The aim of this study was to model the relationship between Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI), Vegetation Condition Index (VCI), Temperature Condition Index (TCI), Vegetation Health Index (VHI), and Standardized Precipitation Index (SPI) at 3-month timescale in Raya and its environs, Northern Ethiopia. This study answered how NDVI and LST, VCI and TCI, SPI and VHI are related. It also explained better drought indices for meteorological and agricultural drought monitoring. MOD11A2 LST Terra, eMODIS NDVI, and monthly rainfall data of the tropical applications of meteorology using satellite and ground-based observations (TAMSAT) were used. The data were analyzed using a simple linear regression model. The results revealed that the mean LST was high (i.e., between 39.6 and 41.29 °C), while NDVI was poor and unhealthy (i.e., below 0.27) in the lowland area due to unfavorable moisture condition than the mid and highland areas. The regression result indicated that NDVI and LST have a relatively strong negative and significant relationship (R2/P = 0.40/0.01 to R2/P = 0.62/0.00) in all districts of the study area. This study also reported that there is a positive and significant relationship between VCI and TCI (R2/P = 0.38/0.02 to R2/P = 0.63/0.00) in all districts of the study area. Furthermore, this study found that the relationship between SPI and VHI is positive and significant (R2/P = 0.36/0.02 to R2/P = 0.60/0.00) in all districts of the study area. The SPI and VHI indices are suitable for monitoring the incidence of meteorological and agricultural drought. This study may help to improve the understanding of both meteorological and agricultural drought indices relationships.