The Role of Sea Surface Temperature Forcing in the Life-Cycle of Mediterranean Cyclones

Abstract

Air–sea interface processes are highly associated with the evolution and intensity of marine-developed storms. Specifically, in the Mediterranean Sea, the air–ocean temperature deviations have a profound role during the several stages of Mediterranean cyclonic events. Subsequently, this enhances the need for better knowledge and representation of the sea surface temperature (SST). In this work, an analysis of the impact and uncertainty of the SST from different well-known datasets on the life-cycle of Mediterranean cyclones is attempted. Daily SST from the Real Time Global SST (RTG_SST) and hourly SST fields from the Operational SST and Sea Ice Ocean Analysis (OSTIA) and the NEMO ocean circulation model are implemented in the RAMS/ICLAMS-WAM coupled modeling system. For the needs of the study, the Mediterranean cyclones Trixi, Numa, and Zorbas were selected. Numerical experiments covered all stages of their life-cycles (five to seven days). Model results have been analyzed in terms of storm tracks and intensities, cyclonic structural characteristics, and derived heat fluxes. Remote sensing data from the Integrated Multi-satellitE Retrievals (IMERG) for Global Precipitation Measurements (GPM), Blended Sea Winds, and JASON altimetry missions were employed for a qualitative and quantitative comparison of modeled results in precipitation, maximum surface wind speed, and wave height. Spatiotemporal deviations in the SST forcing rather than significant differences in the maximum/minimum SST values, seem to mainly contribute to the differences between the model results. Considerable deviations emerged in the resulting heat fluxes, while the most important differences were found in precipitation exhibiting spatial and intensity variations reaching 100 mm. The employment of widely used products is shown to result in different outcomes and this point should be taken into consideration in forecasting and early warning systems.

Wind and wave extremes associated with tropical‐like cyclones in the Mediterranean basin

“…Beginning with the cases employed for the study, 52 events (Table 1) were simulated out of an analytic list of medicane events provided by (Nastos et al ., 2018), enriched by a few more reported cases (McTaggart‐Cowan et al ., 2009; Stathopoulos et al ., 2020a). The modelled cyclones cover all (or a vast majority of) the events (to the best of our knowledge) of a 25 year period.…”

“…For each cyclone, phase diagrams have been derived to define whether it has tropical characteristics at least for a single moment during its life span. It should be noted here that it is already proved in other studies that the lateral and boundary conditions, the model physics and the parameterizations used have a significant effect on the evolution of cyclones (Pytharoulis et al ., 2018; Stathopoulos et al ., 2020a). This is the reason why each cyclone was examined thoroughly and independently but also why there is also a small amount of cases included that do not cover strictly the criteria (e.g., B values close but not greater than 10).…”

“…The structural evolution of the cyclones during their lifespan is made in terms of the thermal core structure and thickness asymmetry. The description of these features is made employing phase diagrams (Hart, 2003; Pytharoulis et al ., 2018; Stathopoulos et al ., 2020a).…”

“…Medicanes have drawn the attention of the scientific community with a range of studies focusing on their genesis (Emanuel, 2005; Chaboureau et al ., 2012; Raveh‐Rubin and Flaounas, 2017) and their evolution (Pytharoulis et al ., 2000; Claud et al ., 2010; Flaounas et al ., 2015). Concerning the last, many analyse the air–sea interactions and their impact on the evolution of the systems (Emanuel, 2005; Fita et al ., 2007; Miglietta et al ., 2011; Tous et al ., 2013; Akhtar et al ., 2014; Pytharoulis et al ., 2018; Stathopoulos et al ., 2020a).…”

Characterization of medicanes with a minimal number of geopotential levels

“…To this end, we select three intense and long‐lasting medicanes that have been reported in previous studies. We choose medicanes ‘Rolf’ (6–9th November, 2011; Ricchi et al ., 2017; Dafis et al ., 2018), ‘Celeno’ (14–17th January, 1995; Pytharoulis et al ., 2006) and ‘Zorbas’ (27 September–1st October 2018; Stathopoulos et al ., 2020). These medicanes present, according to previous data and also in our analysis, a deep warm core over more than 24 hr (as seen in Figure 11).…”