The Survival of Ice Particles Falling from Cirrus Clouds in Subsaturated Air

The influence of radiation on ice crystal spectrum in the upper troposphere

“…The heat balance of an ice crystal in a rarefied atmosphere is represented by the following form (Hall and Pruppacher, 1976;Roach, 1976;Stephens, 1983;Hallett, 1987;Hallett et al, 2002):…”

“…where T s and T e refer to the ice crystal surface and the environmental air temperature, respectively; ρ v and ρ si denote the density of the ambient water vapour and saturated water vapour near a crystal, respectively; S denotes crystal surface area; f m and f Q are the ventilation factors expressed in Hall and Pruppacher (1976). Other factors are:…”

“…For a spherical crystal of radius r, C = r. (2) D -the diffusivity of water vapour in air that is described by Hall and Pruppacher (1976):…”

“…Previous studies have proposed that radiation affects the diffusional growth of ice crystals (Hall and Pruppacher, 1976;Stephens, 1983;Hallett, 1987;Hallett et al, 2002). Stephens (1983) showed that radiation significantly increases the survival distance of falling ice crystals in an unsaturated environment.…”

Cloud parameterization for climate modeling: Status and prospects

“…The effective fall speed can be further reduced by mesoscale rising motion and/or convective lofting associated with the cirrus clouds themselves. Crystals are capable of surviving for extended periods as they fall through subsaturated air (e.g., Hall and Pruppacher, 1976).…”