Monthly and annual variations in the rainfall pattern along the Southern Levantine Coastline

Monthly and annual rainfall variations along the southern Levantine Basin were studied using a 12-year time data series (2009-2020) from six locations: Marsa Matrouh, Alexandria, Rosetta, Damietta, Port Said, and Arish, from west to east, respectively. The general statistics were calculated in addition to the coefficients of variations, the seasonal variation index, the precipitation index, and the cross-correlations. The highest mean monthly rainfall occurred in January (Marasa Matrouh and Rosetta), in November (Alexandria, Damietta and Port Said) and in March (Arish). The lowest mean monthly rainfall for all locations was in September. The highest annual amount of rainfall was 441.1 mm in 2020 in Rosetta, while the minimum was 22.56 mm in 2010 in Marsa Matrouh. The southern border of the Levantine received 8193.61 mm of rainfall over the period 2009-2020, with a precipitation rate of 2.28 mm/rainy day. Alexandria had the highest rate (3.33 mm/rainy day), while Arish had the lowest rate (1.78 mm/rainy day). On the other hand, Port Said had the highest number of rainy days (701 days), while Arish had the lowest number (566 days). Five locations exhibited seasonal rainfall in 3 months or less with high concentration except Marsa Matrouh where long dry seasons persisted. The indices of seasonal variations and precipitation concentration showed that rainfall is highly seasonal and highly concentrated in five locations receiving rainfall in three months but Marsa Matrouh, which has markedly seasonal rainfall regime with a long dry season. The cross-correlations suggested two distinct rainfall zones along the southern Levantine Basin: zone 1 extends from Marsa Matrouh to Port Said and zone 2 comprises only Arish. The rainfall variability along the southern Levantine coastline is substantially higher on a monthly or seasonal basis than on a yearly basis, and its spatial distribution is heavily influenced by local factors such as topography and location.