Teleconnections between Ocean-Atmosphere Coupled Phenomenon and Droughts in Tigray Region: Northern Ethiopia

Abstract

Abstract Existing limited understanding on the teleconnections between ocean-atmosphere coupled phenomena and drought occurrences in Ethiopia has been undermining the decisions and interventions related to climate change adaptation and mitigation. Two drought indices Standardized Precipitation Index (SPI) and Reconnaissance Drought Index (RDI) were usedfor correlation and lag correlation with global indices (El-Nino Southern Oscillation (ENSO), Oceanic Nino (Nino3.4), Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO). The indices were obtained from their respective database websites of the National Center for Environmental Prediction (NCEP). Historical EL-Nino and La-Nina years and Ethiopian drought years were collected from literatures. Meteorological data for seasonal mean rainfall, maximum and minimum temperatures and Potential Evapo-transpiration (PET) of stations (1916-2016) were collected from Tigray regional meteorology agency. In addition, the Cru/Model data was collected from KNMI climate explorer. The analysis shows that the deficiency of (July-Sept) rain in 1972, 1982, 1987 and 1997 is linked with ENSO events. Likewise, deficient and abundant rains in Apr-June appeared to be influenced by the ENSO events. The July-Sept and Apr-June seasonal mean of Southern Oscillation Index (SOI) is positively and negatively correlated to the July-Sept and Apr-June rains in the region, respectively. The Sea Surface Temperature (SST) of central and eastern Pacific (Nino 3.4) is negatively correlated to July-Sept rains and positively correlated to Apr-June rains. In addition to El Nino impacts, other events such as PDO, SOI and IOD are important factors for triggering meteorological and agricultural droughts in Tigray region. The information in this study will serve as inputs to improves seasonal forecast.