Cyclonic activity in the Mediterranean region from a high-resolution perspective using ECMWF ERA5 dataset

Abstract

This study focuses on developing a new Cyclone Detection and Tracking Method (CDTM) to take advantage of the recent availability of a high-resolution reanalysis dataset of ECMWF ERA5. The proposed algorithm is used to perform a climatological analysis of the cyclonic activity in the Mediterranean Region (MR) into a 40-year window (1979–2018). The tuning of the new CDTM was based on the comparison with currently available CDTMs and verified through careful subjective analysis to fully exploit the finer details of MR cyclones features. The application of the new CDTM to the ERA5 high-resolution dataset resulted in an increase of 40% in the annual number of cyclones, mainly associated with subsynoptic and baroclinic driven lows. The main cyclogenetic areas and seasonal cycle were properly identified into the MR context, including areas often underestimated, such as the Aegean Sea, and emerging new ones with cyclogenetic potential such as the coast of Tunisia and Libya. The better cyclone features description defined three distinct periods of cyclonic activity in the MR with peculiar and persistent characteristics. In the first period (Apr–Jun), cyclones develop more frequently and present higher velocities and deepening rates. In the second (Jul–Sep), the cyclonic activity is governed by thermal lows spreading slowly over short tracks without reaching significant depths. In the last and longest season (Oct–Mar), cyclones become less frequent, but with the highest deepening rates and the lowest MSLP values, ranking this period as the most favourable to intense storms.

Climatology of cyclones in western and northwestern Iran using reanalysis and remote sensing data

“…Cyclones mostly formed at 0000 UTC (45%) followed by a secondary peak at 1200 UTC (32.5%). These characteristics are in agreement with previous studies on western Iran's cyclones (Bayat et al ., 2017) and Mediterranean cyclones (Trigo et al ., 1999; Trigo et al ., 2002; Lionello et al ., 2006; 2016; Campins et al ., 2010; Flaounas et al ., 2016; 2018b; 2019; 2021a; Aragão and Porcù, 2021). These studies showed that overall, the average lifetime of these cyclones is 1 day and that they mostly formed in the eastern Mediterranean region.…”

“…First according to the study of Sainsbury et al . (2020), we averaged the 850 hPa relative vorticity and mean sea level pressure 1‐hourly ERA5 data into 6‐hourly intervals and resampled their spatial resolution from 0.25° to 0.75° because 6‐hourly data can better describe cyclone identification and deepening over the Mediterranean region (Aragão and Porcù, 2021). We identified the cyclones in the domain of 12°–42°N and 15°–60°E as follows: The relative vorticity at the cyclone centre and its eight surrounding neighbour grid points must be greater than 3 × 10 −5 s −1 . The local maximum of the relative vorticity at the cyclone centre must be greater than its eight surrounding neighbour grid points. The cyclone centre location must have lower mean sea level pressure than that of the eight neighbouring grid points. The cyclones must have a lifetime of at least 1 day. The tracking of the cyclones was performed over a domain with a range of 10° longitude and 5° latitude. If there are multiple cyclones in the domain, we choose the cyclone centre with the maximum relative vorticity and lowest mean sea level pressure. …”

Analysis of the Most Intense Explosive Cyclone that Occurred Between 2010 and 2020 in the South Atlantic

“…ERA5's reanalysis benefits from ten years of improvements over the previous one; ERA-Interim (Dee et al, 2011), mainly in the physics model, dynamics, and data assimilation, in addition to the more refined spatial resolution (Hersbach et al, 2020). Recent studies with different objectives and applied to different regions have utilized this newer reanalysis, for example, Gramcianinov et al (2020), Aragão andPorcù (2022), andPezzi et al (2022). Satellite data from the Geostationary Environmental Satellite (GOES-16) were also used in the infrared (channel 13 -10.36 μm) and water vapor (channels 7, 8, and 9 -6.2 μm; 6.9 μm; 7.3 μm for high, medium and low levels, respectively).…”

“…Cyclones are a crucial component in the dynamics of the atmosphere. They develop where the flow favors their growth and play a fundamental role in the hydrological cycle since they carry heat, humidity, and momentum (Peixoto and Oort, 1992;Wallace and Hobbs, 2006;Reboita et al, 2010;Gertler and O'Gorman, 2019;Gramcianinov et al, 2019;Reale et al, 2019;Aragão and Porcù, 2022).…”

Origin of low-tropospheric potential vorticity in Mediterranean cyclones

“…We compute backward trajectories using LAGRANTO (Wernli and Davies, 1997;Sprenger and Wernli, 2015) until 48 h prior to the mature stage of the cyclone (−48 h), which is an adequate time period considering the short life span of Mediterranean cyclones (Trigo et al, 1999;Aragão and Porcù, 2022). Along these, we trace surface pressure, PV, and in the IFS simulations the available PV rates due to different diabatic processes.…”