Innovative Lagrangian Radiosonde Clusters for ABL Observations

We present a novel method to track fluctuations in the atmospheric boundary layer (ABL) using a cluster of mini-radiosondes. Each radiosonde is lightweight, expendable and carried by biodegradable balloons. This system collects statistics of turbulence fluctuations in the ABL and warm clouds within it. The first operational prototype of the radiosonde cluster developed at POLITO was tested in several field campaigns from November 2022 to September 2024. These campaigns, which included six cluster launch experiments, were conducted in collaboration with CNR-INRIM, MET-OFFICE, NCAS, ARPA Piemonte, ARPA-FVG, and OAvdA (see Fig. 1). The system provides critical insights for modeling ABL dynamics and dispersion, a major source of uncertainty in climate and meteorological simulations [1].Figure 1: In-field experiments with the radiosonde cluster network. LoRa P2P radio transmission, 12 km range, 868 MHz, 0.2 Hz data acquisition frequency. Left: radiosonde trajectories. Middle: vertical profiles of temperature and mean Brunt-Vaisala frequency from 3 radiosondes. The purple color indicates positive temperature gradients, while green indicates negative ones. Right: wind speed, magnetic field, and acceleration fluctuation spectra. A) Alpine environment, St. Barthelemy, Aosta, Italy, November 2023. B) Rural near-maritime Atlantic coast, Chilbolton, UK, July 2023, WESCON campaign. C) Subalpine region, Udine, Italy, June 2024. D) Rural near-maritime Atlantic coast, Chilbolton, UK, September 2024. Ground-level wind speeds: A: 1 m/s, B: 17 m/s, C: 0.5 m/s, D: 10 m/s.Each radiosonde is a radioprobe board [1, 2] mounted on a biodegradable balloon [3] filled with a helium-air mixture, allowing a float time of several hours. It measures air temperature, pressure, humidity, and four vector quantities (position, velocity, acceleration, and Earth's magnetic field) along each trajectory (Fig. 1). Passive tracking of multiphase cloud parcels provides a multi-point view of flow structures. Recent experiments have explored turbulent dispersion analysis using a distance neighbor graph algorithm [4], addressing aspects of atmospheric turbulence not previously measured in field observations. The system can advance models for cloud microphysics and turbulence schemes for atmospheric tracer dispersion [5]. Our methodology uses high-frequency atmospheric data and improves understanding of turbulence. This enables advances in cloud modeling, weather prediction, and climate simulation. The biodegradable balloon has a volume of ~40 liters and weighs ~18 grams. Optimizing the size and weight of the circuit board (halving both dimensions) will reduce the balloon volume by 30%, allowing for simultaneous deployment of swarms of ~100 mini-radiosondes. The future radioprobe will have sensors for VOCs, greenhouse gases, and UV radiation integrated into the PCB to expand its use cases. An energy harvesting module will extend the lifetime of the probe.1. Abdunabiev S. et al., Measurement 224, 113879 (2024)2. Paredes et al., Sensors 21, 1351 (2021)3. Basso et al., Mat. Chem. Phys. 253, 123411 (2020)4. Richardson, Proc. R. Soc. Lond. A 110, 709 (1926)5. Mirza et al., Q. J. R. Meteorol. Soc. 150, 761 (2024)