Sebastianelli et al. (2025) Near-surface wind field characterization of medicanes using satellite observations

Identification

• Journal: Atmospheric Research
• Year: 2025
• Date: 2025-12-29
• Authors: Stefano Sebastianelli, Leo Pio D’Adderio, Paolo Sanò, Daniele Casella, Giulia Panegrossi
• DOI: 10.1016/j.atmosres.2025.108734

Research Groups

• Institute of Atmospheric Sciences and Climate, National Research Council of Italy (CNR-ISAC), Rome, Italy

Short Summary

This study characterizes the near-surface wind field of medicanes using satellite scatterometer data and a new algorithm (MeRCAD) to detect the rotational center and radius of maximum wind (RMW). It finds that a significant decrease in RMW (to a few tens of kilometers) and a nearly symmetric wind circulation indicate a medicane's mature phase, often associated with deep convection near the rotational center, distinguishing them from typical extratropical cyclones.

Objective

• To characterize the ocean near-surface wind field of medicanes using satellite scatterometer data to detect their rotational center and radius of maximum wind (RMW) via the newly developed Medicane Rotational Center Automated Detection (MeRCAD) algorithm.
• To demonstrate that ASCAT winds can effectively identify the transition from the development to the mature phase of medicanes.
• To examine the relationship between RMW, PMW-derived warm core (WC) diagnostics, and the occurrence of deep convection (DC) near the cyclone center to better identify medicanes reaching a mature phase and undergoing tropical transition.

Study Configuration

• Spatial Scale: Mediterranean Sea; mesoscale cyclones with typical diameters ranging from 100 kilometers to 300 kilometers (seldom exceeding 400 kilometers). Area of interest (AOI) defined as a 3-degree domain around the minimum mean sea level pressure (MSLP). RMW calculated within a 250-kilometer radius from the rotational center.
• Temporal Scale: Analysis of 10 medicanes that occurred in the Mediterranean basin from 2011 to 2023. Medicane tropical-like characteristics typically last from a few hours to a couple of days.

Methodology and Data

• Models used:
  • Medicane Rotational Center Automated Detection (MeRCAD) algorithm (newly developed for rotational center identification and RMW computation).
• Data sources:
  • Satellite scatterometer: Advanced Scatterometer (ASCAT) on board European MetOp-A, B, C satellites (C-band, 5.255 GHz) for sea surface wind speed and direction (ASCAT Coastal Winds at 12.5 km Swath Grid from EUMETSAT Data Store).
  • Reanalysis data: ECMWF Reanalysis v5 (ERA5) for hourly Mean Sea Level Pressure (MSLP) estimates at 0.25-degree spatial grid (used as a first guess for the rotational center and to delineate the AOI).
  • Satellite passive microwave radiometer: MetOp Microwave Humidity Sounding (MHS) radiometer (89–190 GHz spectral range, specifically 183.3 GHz channels) for deep convection (DC) detection.
  • Satellite passive microwave radiometer: Advanced Microwave Sounding Unit-A (AMSU-A) and Advanced Technology Microwave Sounder (ATMS) (54–55 GHz oxygen absorption band channels) for warm core (WC) detection and characterization.
  • Satellite passive microwave radiometer: MWTS-3 sensor on board Feng-Yun 3F satellites (used for one specific case for WC detection).

Main Results

• The newly developed MeRCAD algorithm successfully identifies the rotational center (RC) and radius of maximum wind (RMW) of medicanes using ASCAT data.
• During the mature phase, when the wind field exhibits a nearly symmetric circulation, the RMW significantly decreases, often to a few tens of kilometers (typically 40-80 kilometers), compared to the development phase where RMW can exceed 100 kilometers.
• The maximum sustained wind (Vmax) in the mature phase is mostly beyond the 95th percentile of values observed for all Mediterranean cyclones, although medicanes remain substantially weaker than tropical cyclones.
• During the tropical transition (TLC) phase, a warm core (WC) is fueled by an area of deep convection (DC) located near the rotational center, at distances shorter than the RMW, showing parallels with tropical cyclone intensification.
• A nearly symmetric wind circulation alone is not sufficient to confirm the mature phase due to the possible absence of a warm core, and conversely, a warm core can exist without a symmetric wind circulation.
• A positive correlation is observed between Vmax and the average variation of MSLP per unit distance (ΔP/ΔR).

Contributions

• First extensive analysis of medicane near-surface wind fields and their evolution using satellite scatterometer data (ASCAT).
• Introduction and validation of the novel Medicane Rotational Center Automated Detection (MeRCAD) algorithm for objective identification of medicane rotational centers and RMW.
• Establishes RMW and the presence of a nearly symmetric wind circulation as key indicators for identifying the transition to the mature phase of medicanes.
• Provides observational evidence linking surface wind characteristics (RMW, symmetry) with thermodynamic (warm core) and microphysical (deep convection) properties, enhancing the understanding of medicane tropical transition.
• Highlights similarities in deep convection location relative to RMW between medicanes in TLC phase and intensifying tropical cyclones.
• Contributes to the refinement of medicane definition by providing detailed observational characteristics of their surface wind structure.

Funding

• European Space Agency’s (ESA) Medicanes project (ESA Contract No. 4000144111/23/I-KE).

Citation

@article{Sebastianelli2025Nearsurface,
  author = {Sebastianelli, Stefano and D’Adderio, Leo Pio and Sanò, Paolo and Casella, Daniele and Panegrossi, Giulia},
  title = {Near-surface wind field characterization of medicanes using satellite observations},
  journal = {Atmospheric Research},
  year = {2025},
  doi = {10.1016/j.atmosres.2025.108734},
  url = {https://doi.org/10.1016/j.atmosres.2025.108734}
}