Thermal Shock as an Ice Multiplication Mechanism. Part I. Theory

Abstract

Thermoelastic theory is used to calculate thermal stresses in ice crystals of idealized shapes when a small area on one surface is warmed to 0°C, in simulation of riming of the crystal by a cloud droplet. It is shown that a typical riming event involving a 20 μm diameter droplet impinging on a 500 μm plate or column would need to occur at a temperature colder than −35°C before fracture could be expected. For a given ice crystal size, the thermal stresses increase with droplet diameter, and thin plates rimed by large droplets are the most sensitive to thermal shock, but still need to be colder than −10°C before fracture would occur. It is consequently concluded that the thermal shock mechanism is unlikely to be responsible for the proliferation of ice crystals in clouds at temperatures as warm as −4°C.