Aerosol–Ice Crystal–Radiation Interactions in Deep Convection: Insights from High-Resolution Meso-NH Simulations and HAIC Observations

Mesoscale convective systems (MCSs) are vital to Earth's climate system, fundamentally influencing water and energy cycles and by driving a large fraction of extreme weather events, including intense precipitation, flooding, and severe winds. A defining characteristic of these systems is their extensive ice anvils, whose shortwave and longwave radiative interactions generate cloud-radiative heating that strongly controls anvil lifetime, organization, and storm evolution. Despite their importance, the representation of deep convective systems remains a major source of uncertainty in weather and climate models, largely due to the complex and tightly coupled interactions between aerosols, cloud microphysics, and radiation. In particular, the role of ice crystal number, size, and habit in modulating radiative heating profiles and feedbacks on convective dynamics is still poorly constrained.

The High Altitude Ice Crystals (HAIC) field campaign provides a unique observational framework to investigate these processes. HAIC combined in situ airborne microphysical measurements with satellite observations to document the properties of ice crystals in deep convective structure, with a specific focus on high ice water content conditions relevant for both climate processes and aviation safety. During the campaign, detailed observations of ice crystal concentrations, size distributions, and thermodynamic conditions were collected in tropical deep convective systems, offering an exceptional opportunity to evaluate and constrain model representations of ice microphysics and their radiative impacts.

In this study, we focus on a well-documented deep convective system that formed over the Atlantic Ocean and was advected toward French Guiana on 16 May 2015. We combine HAIC airborne and satellite observations with high-resolution numerical simulations performed with the Meso-NH model. The simulations employ the two-moment LIMA microphysical scheme, explicitly coupled to the ecRad radiative transfer code. The radiative properties of ice crystals are prescribed using habit-dependent optical parameterizations derived from the Yang et al. (2013) ice optics lookup tables. Aerosol sources, transport, activation, and scavenging are explicitly represented, allowing an assessment of how aerosol variability propagates through cloud microphysical processes and radiative feedbacks. This configuration allows a physically consistent representation of aerosol–microphysics–radiation interactions. Sensitivity experiments are performed to investigate both aerosol life-cycle effects and ice crystal habit variability, while keeping the large-scale dynamical forcing unchanged. Dedicated sensitivity simulations are conducted by systematically testing distinct ice crystal habits in order to isolate their respective impacts on cloud-radiative heating profiles, anvil structure, precipitation efficiency, and convective lifecycle. This combined observational–modeling framework provides quantitative insight into how aerosol processes and ice microphysical properties jointly modulate radiative feedbacks in deep convection.