Satellite-based studies of the evolution of the Ianos medicane dynamics

Using the general analogies with the descriptive models of the tropical cyclones, some climate change effects identify a significant increase in the Mediterranean sea surface temperature. This phenomenon, in conjunction with its peculiar morphological predisposition, could justify the acceleration, recently observed, and the formation of cyclones at these latitudes, so-called medicanes (“MEDIterranean HurriCANES”). Their observations are based on a typical rotational motion around a low-pressure center in the atmospheric mesoscale, including the air-sea interaction effects.

In this work, different kinds of analyses were carried out about the spatial and temporal evolution of the Ianos medicane (Mediterranean cyclone that developed in 2020 in the middle of the Ionian sea). In particular, we use the Proper Orthogonal Decomposition (POD) method to decompose a database of spatio-temporal data collected by SEVIRI radiometer, onboard the Meteosat Second Generation - 11 geostationary satellite. Within this approach, we study the superposition regions of the rotating air masses, starting from the temperature field, in order to extract important informations about the evolution and distribution of the energy in the different scales of the event. Through this technique, it has been possible to study the turbulent dynamics of Ianos at different scales, obtaining a basis of empirical eigenfunctions along with their relative temporal coefficients. The ability of the POD to capture the maximum energy content in the spectrum, allows to separate different ranges of scales with similar characteristics, suggesting a different origin for the various kinds of emerging structures.

On the other hand, through the use of specific remote sensing techniques, the diagnostics of Ianos were studied using databases obtained from LEO satellites. The capabilities of the VIIRS and MODIS sensors, on board the Suomi NPP and EOS-Terra/Aqua platforms, which have 2D images with higher spatial resolutions, were explored. The aim of this analysis is based on the extraction of some atmospheric parameters, such as the temperature field within the Ianos cloud system, associated with altitude values, and the assessment of the ice pixel percentage using the split window. In addition, a study of atmospheric instability was carried out using the vertical temperature gradient and sea surface temperature, and the pressure field for the characterization of the minimum in the eye of the cyclone.