Deciphering the mysteries of hailstone formation: Linking satellite and physicochemical studies of hail in Argentina

Abstract

This dissertation advances our understanding of hail formation processes and environments in Argentina, a global hail hotspot, through a multi-scale analysis spanning from individual particles to storm-scale characteristics. First, we introduce an innovative microscopy analysis methodology that preserves in-situ non-soluble particles within hailstones using a protective porous plastic coating. This method combines confocal laser scanning microscopy and scanning electron microscopy with energy-dispersive spectroscopy to analyze particle characteristics while maintaining their spatial distribution within the hailstone structure. Applying this methodology to hailstones collected in central Argentina reveals how different storm modes access distinct particle populations. In supercell environments with strong upslope flow, particles originate primarily from local sources, while organized systems associated with the South American Low-Level Jet incorporate particles from more distant regions. Particle sizes reach 256 microns, with agglomerated mineral/organic particles dominating the composition, demonstrating how regional land use patterns influence potential ice nuclei availability. We then examine environmental conditions supporting hail production by combining GOES-East Overshooting Top detections with Global Precipitation Measurement Dual-frequency Precipitation Radar (GPM-DPR) hail detection data (2014-2022). Larger and deeper OTs occur in environments characterized by higher moisture content and elevated wet bulb zero heights, particularly when combined with steeper mid-level lapse rates. The strong negative correlation between OT area and IR-tropopause temperature difference (r = -0.72) indicates that larger OTs consistently achieve deeper penetration. Environmental conditions show distinct diurnal patterns, supporting both afternoon discrete storms with peak MUCAPE (~3000 J/kg) and nocturnal organized systems with enhanced wind shear (median ~16 m/s in hail-matched cases). These patterns reveal how Argentina's hail-producing environments support a broader range of storm modes compared to U.S. storms. The diversity in storm modes and environmental conditions helps explain why Argentina experiences significant hail production across a wider variety of atmospheric conditions, particularly through the interaction between the South American Low-Level Jet and local terrain features.This research provides new insights into how particle characteristics and environmental conditions interact to support hail formation in Argentina while developing methodological approaches that can be applied to study severe storms in other traditionally under-observed regions globally.