Mediterranean Sea heat uptake variability as a precursor to winter precipitation in the Levant

Abstract. The Eastern Mediterranean is experiencing severe warming and drying, associated with global warming, making seasonal prediction of precipitation in the region imperative. Given that the Mediterranean Sea is the primary source of regional moisture and synoptic variability, here we explore the observed relation of Mediterranean Sea variability to Levant land precipitation during winter – the dominant wet season. Using Self-Organizing Map objective analysis, we identify three dominant modes of sea surface temperature (SST) and ocean heat uptake variability in the Mediterranean Sea. Of these, two modes characterized by east-west variations are found to be statistically related to winter land precipitation in the Levant. Based on these relations, we define an Aegean Sea heat uptake anomaly index (AQA), which is strongly correlated with Levant winter precipitation. Specifically, AQA values during August are found to predict Levant precipitation in the following winter (R = -0.6). Wetter winters over the Levant following negative August AQA values are associated with more persistent eastward-propagating Mediterranean storms, driven by enhanced baroclinicity and a stronger subtropical jet. The results present AQA as a useful seasonal predictor of Levant winter precipitation, and indicate that the representations of processes affecting Mediterranean cyclones, the subtropical jet, and ocean-atmosphere heat exchange, are key for seasonal forecasting skill in the Levant.