Ground-Based Estimation of Low-Altitude Turbulence Over Milan for Safer Airship and UAV Operations

Reliable characterization of atmospheric turbulence in the urban boundary layer is critical for the flight safety and structural integrity of light aerial platforms operating below 300 m. For unmanned airships, in particular, turbulence represents a well-known complication factor due to their large aerodynamic surfaces and low-speed flight regimes. An accurate understanding of near-ground conditions is essential for these vehicles, especially in Milan, where experimental activities are scheduled as part of the IPROP project. However, conventional high-resolution sensing infrastructure is often too costly or spatially sparse for real-time deployment. This study proposes a low-cost turbulence-intensity proxy, TI_b, derived from standard 10-minute ground-based meteorological data. The metric is defined as TI_b(t) = α|dU/dt|+βσ_U, capturing both impulsive shear transients and stochastic fluctuations.

The methodology was evaluated using data from two Milanese stations during April–May 2025: Lambrate (suburban) and P.zza Zavattari (dense urban core). The results show that the suburban site exhibits higher dynamic activity, with a mean TI_b of 0.142 and peak excursions exceeding 0.36, indicating frequent shear-driven bursts. Conversely, the urbancore shows a smoother environment with a mean TI_b of 0.097. This work maps these proxies to three operational risk categories—Nominal, Elevated Workload, and Caution—providing a practical heuristic for mission planning. The findings underscore the necessity of localized hazard mapping for Urban Air Mobility (UAM) and experimental airship operations in complex metropolitan airspaces.