INVESTIGADORES
AVILA Eldo Edgardo
artículos
Título:
A laboratory study of the effects of rime ice accretion and heating on charge transfer during ice crystalrgraupel collisions
Autor/es:
C. P. R. SAUNDERS; E. E. AVILA; S.L. PECK; N.E. CASTELLANO; G. G. AGUIRRE VARELA
Revista:
ATMOSPHERIC RESEARCH
Editorial:
ELSEVIER
Referencias:
Año: 1999 vol. 51 p. 99 - 117
ISSN:
0169-8095
Resumen:
In a laboratory study of thunderstorm electrification involving charge transfer between ice
crystals and a riming graupel pellet, the effect on charge transfer of rimer heating by droplet
accretion has been separated from the associated influence of the vapour flux to the rimer surface.
This was accomplished by heating internally a riming target rod whose surface conditions
represent those of a falling graupel pellet in thunderstorms while keeping the rate of rime
accretion constant. The results show that the positive charging of a rimer may be reversed to
negative by artificial heating, with increased heat required at higher rates of rime accretion. It is
hypothesised that ice crystals rebounding from riming graupel pellets charge the graupel positively
or negatively depending on the cloud and rimer conditions, which influence the relative thicknesses
of charge carrying layers on the surfaces of the particles. In the natural case, negative
charging of graupel is associated with rime surface heating, which reduces the vapour diffusional
growth rate below that of the ice crystals, while positive charging of graupel is associated with
vapour provision to the rimer surface from the freezing droplets, which overcomes the rime
heating effect. This work compares the results of charge transfer to a riming target obtained in
UMIST Manchester, involving multi-crystal interactions, with data from Cordoba Argentina
involving single ice sphere interactions. The fact that broadly similar charging behaviour was seen
in both studies suggests that it is the rate of growth of the ice surfaces, rather than their particular