Recent changes in continentality and aridity conditions over the Middle East and North Africa region, and their association with circulation patterns

A long-term (1960-2013) assessment of the variability of continentality and aridity conditions over the Middle East and North Africa (MENA) region was undertaken. Monthly grid-ded temperature and precipitation data fr om the Climate Resear ch Unit (CRU) (TS3.22 version) wer e used to compute the Johansson Continentality Index (JCI) and the Marsz Oceanity Index (MOI). In addition, the De Martonne index and the Pinna index wer e employed to assess r ecent changes in aridity conditions. All indices revealed a statistically significant increase in continental influences over the r egion, particularly in the Nile Basin and the Fertile Crescent. For aridity, the results suggested a generally statistically insignificant increase, with the most rapid changes occurring over the most humid regions (i.e. the Ethiopian Highlands and the Fertile Crescent). In order to explain the observed changes in the continentality and aridity conditions, we assessed the relationship between aridity and continentality indices and a wide range of large-scale circulation patterns. Results indicate that the spatial variability of continentality (as well as aridity) was closely coupled with the Atlantic modes of variability, e.g. the Easter n Atlantic pattern and the Atlantic Meridional Mode, compared to those of the Mediter ranean Sea and the Indian Ocean. The results of this work highlight change pr ocesses in 2 important climate features in one of the hottest regions on Earth. Improving our understanding of the spatio-temporal characteristics of cli-mate continentality and aridity has implications for a diversity of socio-political, economic, hydro-logical, and ecological activities in the MENA region.