| ABSTRACT | This study is the first to identify objectively 'parent-daughter' relationship between cyclones and is applied for the Mediterranean cyclones (MCs). The aim of the study is to explore the sources of MCs by identifying their parents and tracking them back several generations.
The study analyzes MCs that lasted for at least 24 hours, based on the ECMWF interim data for 30 mid-winter (DJF) seasons. The tracking algorithm is based on common methods, with modifications done for coping with the irregularities of the Mediterranean resulting from the complex terrain. The parenthood was determined while a cyclogenesis took place within a 2.25 range of the influence area of an existing cyclone, defined as the 'parent' cyclone. The influence area of a cyclone was defined as the continuous area extending from its center where the pressure rises and the flow is cyclonically curved.
The analysis indicated that 97% of the 3,202 MCs generated within the Mediterranean have parents. Surprisingly, most of the parents (61.4%) are found within the Mediterranean itself and the rest are from the Atlantic, Europe and North Africa, including the Red Sea. Exploration of previous generations was done by tracking back the chain of parents, grandparents etc. down to the 9th generation. The birth location of the earliest parents found for a certain MC is considered as its source. It is shown that the primary source regions are the Atlantic (64%) and Equatorial Africa and southern Red Sea (23%), and the secondary are southern Europe (5%) and the Mediterranean itself (8%).
Our results indicate that the majority of MCs owe their existence to the Atlantic – European cyclone track and to the cyclogenetic character of the MB. It can be concluded that the Mediterranean cyclogenesis is manifested in two ways; one is the tendency of cyclones to be generated whenever a cyclone passes in the area surrounding the Mediterranean, e.g., the eastern Atlantic or south Europe, and the second is the 'self maintaining' nature of the MCs, i.e., when an MC is formed, it has a high probability to produce a daughter MC and so on. |