Publication

Investigating Secondary Ice Production effects on wintertime orographic clouds using the Regional Atmospheric Modelling System (RAMS)

2025

Abstract

In recent years, there has been a breakthrough in the identification and description of various secondary ice production (SIP) mechanisms that affect mixed-phase clouds. However, SIP is in general not described well in climate and mesoscale models, which leads to notable biases in the representation of warm mixed-phase clouds in terms of ice content, ice number concentration and cloud structure. In this study, the Integrated Community Limited Area Modelling System (ICLAMS) has been utilized to examine the formation and evolution of wintertime orographic clouds over Mt. Helmos, Greece. ICLAMS is a special version of the Regional Atmospheric Modelling System (RAMS). In addition to the Hallett-Mossop process, already included in the model, two additional SIP mechanisms are implemented, a) collisional break-up of ice particles and b) droplet shattering. Model results are evaluated against in-situ and remote sensing observations collected during the CleanCloud CHOPIN campaign (https://go.epfl.ch/chopin-campaign) at Mt. Helmos in the Peloponnese, Greece during Fall 2024 to Spring 2025. Remote sensing (wind lidar and cloud radar) data are used to evaluate model performance, through the application of forward operators (cloud radar simulator) and comparison with radar reflectivity and turbulence parameters. The mesoscale model simulations indicate that SIP enhances aggregation and results in clouds with increased ice crystal number concentrations, aligning more closely with observed distributions. Among the SIP mechanisms, collisional break-up is identified as the dominant contributor to simulated SIP rates, underscoring its critical role in accurately representing orographic mixed-phase clouds.

Official source

https://infoscience.epfl.ch/entities/publication/5e7e653f-dbd4-4db9-b8c1-cbfb8a87d6cb

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2025

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/5e7e653f-dbd4-4db9-b8c1-cbfb8a87d6cb

About this result

Related concepts (32)

Atmospheric model

In atmospheric science, an atmospheric model is a mathematical model constructed around the full set of primitive, dynamical equations which govern atmospheric motions. It can supplement these equations with parameterizations for turbulent diffusion, radiation, moist processes (clouds and precipitation), heat exchange, soil, vegetation, surface water, the kinematic effects of terrain, and convection. Most atmospheric models are numerical, i.e. they discretize equations of motion.

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Ice is water frozen into a solid state, typically forming at or below temperatures of 32 °F, 0 °C, or 273.15 K. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color. In the Solar System, ice is abundant and occurs naturally from as close to the Sun as Mercury to as far away as the Oort cloud objects. Beyond the Solar System, it occurs as interstellar ice.

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Investigating Secondary Ice Production effects on wintertime orographic clouds using the Regional Atmospheric Modelling System (RAMS)

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