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Lebanon, with its geographic location facing the Mediterranean Sea and dominant rugged topography, is characterized by a strong climatic variability even between zones located few kilometres apart. The investigation of the climatic indices is necessary to delineate such diverse climatic situation over Lebanon. In this context, this paper investigates the periodic behaviour in annual Emberger aridity index (AI(E)) of 14 weather stations in representative sites of Lebanon. The AI(E) indicates that the dominant climate of Lebanon, which is mainly varying from humid to semi-arid, follows cyclonic meteorological patterns. The periodicities of AI(E) identified by using a robust technique seem almost altitude related and range between 2 and 21years. The geographic distribution of periodicities implies two major zones in the northern and southern parts of Lebanon, being featured by longer and shorter periodicities, respectively. The formation of these two periodicity zones can be related to regional climatic zoning. The remarkable diversity in periodicity indicates predominant microclimates with specified cyclonic climate that characterizes Lebanon's climate rather than a merely existence of climate change.