The tropical nature of an intense Mediterranean cyclone in the ocean-atmosphere system

Certain intense Mediterranean cyclones display characteristics of tropical cyclones: they have an axisymetric cloud cover with an eye-like feature visible in satellite images and some produce a cold wake evidenced by remotely sensed sea surface temperature anomalies.  Such cyclones have been labeled as medicanes (Mediterranean hurricane) although no precise definition exists for classifying these hybrid systems. Current efforts in the research and operational communities seek to better understand medicanes through targeted case studies.

Here we used a coupled model framework to detail the tropical characteristics of the cyclone Ianos which hit Greece during the third week of September 2020. Ianos produced a cold wake which was captured in sattelite imagery and in argo float profiles. A series of  high resolution (1.8 km) coupled ocean-wave-atmosphere simulations allows us to assess the dynamics of Ianos in both the atmosphere and the ocean compartiments, as well as their interactions. We compare the results with the typical behaviour of tropical and extratropical cyclones. The coupled framework consists of the atmospheric model Meso-NH, the 3rd generation wave model WAVEWATCH III®, and the oceanic model CROCO.  We contrast the impact of ocean-atmosphere coupling without waves to full 3 way coupling with and without sea spray physics. Waves and sea spray accentuate the asymmetry of the storm with impacts reaching beyond the marine boundary layer. Two separate cold wakes are formed with large scale freshening in the second one. These have a negative impact on the cyclone's intensity. Ocean temperature budget analysis allows distinguishing key processes and interplay between storm induced and local ocean dynamics.  Available in situ and satellite-borne observations are used to validate results.