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K. A. Browning
,
J. Hallett
,
T. W. Harrold
, and
D. Johnson

Abstract

Attempts have been made to obtain samples of freshly fallen hailstones from severe storms in Oklahoma with the purpose of studying the nature and extent of spongy ice within natural hail. Interception by automobile of radar echoes with Ze > 105 mm6 m−3 has been found to provide a workable technique for collecting large hailstones as they fall to the ground. Observations suggest that the regions of highest reflectivity were associated more closely with the falls of large hail than with the accompanying heavy rain.

Immediate sectioning of the freshly fallen hailstones revealed the presence of thin shells of spongy ice in many of the larger stones. Calorimetric analyses gave liquid water contents of up to 12 ± 4% of the mass of the stones. Some of the hailstones were aspherical owing to preferential melting of the regions of spongy ice during fall. In the case of hailstones that were stored at sub-freezing temperatures, spongy ice shells could often still be identified from the presence of millimeter size cavities embedded within ice composed of large crystals.

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C. P. R. Saunders
,
R. L. Pitter
,
B. A. Gardiner
, and
J. Hallett

Abstract

A system is described for measurement and analysis of precipitation particle charge from an aircraft in the highly variable and harsh environment of a convective cloud. A compromise, practical instrument design enables particle charge and sign to be measured with concentrations up to 5 L−1. The system employs two induction rings in series; it is de-iced both on the electrostatic shield and internally. New techniques are described which enable rapid analysis of sequential charge data over a penetration period of 55 s, with rejection of spurious data pulses resulting from particle impaction.

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