Teleconnections between ocean-atmosphere circulations and historical integrated drought in the Middle East and North Africa.

Abstract

In the Middle East and North Africa (MENA) with extreme water scarcity worldwide, drought significantly impacts various aspects of the local people. This study uses the empirical multivariate standardized drought index (MSDI), wavelet power spectrum, and a blind source septation technique of independent component analysis (ICA) to unravel linkages between Atlantic- and Pacific-based climate indices and MENA's drought between Jan 1979 and Dec 2016. It is found that drought in the eastern MENA is more than its western linked to climate indices. PDO, ENSO, and AMO, on the whole, have statistically stronger correlations with the MENA's drought than NAO (absolute R2 is less than 0.17, 0.22, and 0.21 for interannual, decadal, and interdecadal modes, respectively). The blind sources extracted by ICA confirm the higher impacts of PDO (R2 = 0.39), ENSO (R2 = 0.30), and AMO (R2 = 0.38) on the Middle East's drought. PDO's modulation linkage to MENA's drought occurs from interannual to decadal, and interdecadal variability cycles. ENSO largely impacts the 2-7-year interannual (R2 = 0.40-0.48 for the Middle East) and 8-12-year decadal (R2 = 0.18-0.30) drought cycles, while the PDO more affects 8-12-year decadal (R2 = 0.29-0.58) modes. The interdecadal (30-50-year) variability of MENA's drought mostly correlates with AMO and PDO. Overall, the interannual droughts are mostly controlled by ENSO while the decadal by PDO. For the interdecadal droughts, PDO and AMO are the most important in the Middle East and the western MENA, respectively. This study highlights that an integrated drought signal is not solely derived from a single climate index since each index may modulate a specific drought variability mode that may differ from other indices. The physical mechanisms behind these observations are further described.