Evaluation of the Sensitivity of Medicane Ianos to Model Microphysics and Initial Conditions Using Satellite Measurements

Albert Comellas Prat,Stefano Dietrich,Rosa Claudia Torcasio,Giulia Panegrossi,Leo Pio D’Adderio,Stefano Federico

doi:10.3390/rs13244984

Albert Comellas Prat, Stefano Dietrich + Show 4 more

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https://doi.org/10.3390/rs13244984

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Abstract

Tropical-like cyclone (TLC or medicane) Ianos formed during mid-September 2020 over the Southern Mediterranean Sea, and, during its mature stage on days 17–18, it affected southern Italy and especially Greece and its Ionian islands, where it brought widespread disruption due to torrential rainfall, severe wind gusts, and landslides, causing casualties. This study performs a sensitivity analysis of the mature phase of TLC Ianos with the WRF model to different microphysics parameterization schemes and initial and boundary condition (IBC) datasets. Satellite measurements from the Global Precipitation Measurement Mission-Core Observatory (GPM-CO) dual-frequency precipitation radar (DPR) and the Advanced Scatterometer (ASCAT) sea-surface wind field were used to verify the WRF model forecast quality. Results show that the model is most sensitive to the nature of the IBC dataset (spatial resolution and other dynamical and physical differences), which better defines the primary mesoscale features of Ianos (low-level vortex, eyewall, and main rainband structure) when using those at higher resolution (~25 km versus ~50 km) independently of the microphysics scheme, but with the downside of producing too much convection and excessively low minimum surface pressures. On the other hand, no significant differences emerged among their respective trajectories. All experiments overestimated the vertical extension of the main rainbands and display a tendency to shift the system to the west/northwest of the actual position. Especially among the experiments with the higher-resolution IBCs, the more complex WRF microphysics schemes (Thompson and Morrison) tended to outperform the others in terms of rain rate forecast and most of the other variables examined. Furthermore, WSM6 showed a good performance while WDM6 was generally the least accurate. Lastly, the calculation of the cyclone phase space diagram confirmed that all simulations triggered a warm-core storm, and all but one also exhibited axisymmetry at some point of the studied lifecycle.

Highlights

All simulations initialized with Global Forecast System (GFS) showed a significant downward trend in rainwater content, with lower values at the end of the simulations than at 6 h after the start; on the other hand, those initialized with ECMWF data showed a generally steady evolution (Figure 3a)
If we look at the integrated frozen hydrometeor content, we can appreciate again a decreasing trend in the GFS simulations and overall stable evolutions for the ECMWF simulations
UTC 17 September, we can find that (i) the observed mean integrated rainwater content for the area of 100 km radius from the cloud-free eye was 1.24 mm, falling within the range of values of the ECMWF-based experiments (~0.9–1.3 mm), whereas those with GFS data varied between roughly 0.4 and 0.65 mm, and (ii) the observed integrated frozen hydrometeor areal mean was 0.29 mm, only very slightly overestimated by WSM6 and WDM6 GFS at 0.30–0.40 mm, while all other simulations largely overestimated it with values between ~1.2 mm (Morrison GFS) and ~2.45 mm (Thompson ECMWF)

Summary

Introduction

Some densely populated areas in the Mediterranean basin are prone to suffering the impacts of the infrequent but highly destructive tropical-like cyclones (TLCs), known as Mediterranean hurricanes (medicanes), a local type of storm system that shares some characteristics with tropical cyclones (TCs) [1,2,3]. Like TCs, medicanes are intense lowpressure systems with strong surface winds, a calm cloud-free eye, spiraling cloud bands expanding from the center, weak vertical wind shear, and an axisymmetric structure with a warm-core anomaly. 2021, 13, 4984 latent heat release play important roles in their intensification and maintenance phases. They show important differences from TCs such as (1) their reduced size between Remote Sens. 2021, 13, 4984 latent heat release play important roles in their intensification and maintenance phases.

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