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Wayne R. Sand

Abstract

This study relates data gathered during the penetration of hailstorms between 4.9 and 6.7 km MSL by an armored T-28 aircraft to detailed radar data of the hailstorms penetrated. These data recorded by the T-28 data system are combined with observations made by the author while piloting the T-28 through hailstorms. The radar data from the National Hail Research Experiment CPR-2 are specially prepared as Constant Altitude Plan Position Indicator (CAPPI) displays and vertical sections along the aircraft track for comparison with the data gathered by the aircraft system and pilot's observations.

The results indicate that significant updrafts are frequently found well ahead of the high radar reflectivity zones. The updrafts are found to be relatively smooth while the high radar reflectivity zones are found to be very turbulent. Significant quantities of supercooled liquid water are found in the updraft regions. Significant airframe icing is found in the strong updrafts with the most severe icing along the edges of the updrafts. The high reflectivity zones are found to contain almost exclusively ice. Hail is more frequently found in the area of strong reflectivity but small hail is found outside the 40 dBZ contour.

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Thomas G. Kyle
,
Wayne R. Sand
, and
D. J. Musil

Abstract

Twelve thunderstorm updrafts were analyzed in detail and a composite average derived. The updrafts were normalized in width and maximum intensity so they could he compared on the same scale. The composite average was compared with the Gaussian and the polynomial curves frequently used by modelers to describe some updraft characteristics. The composite average was also compared with an axially symmetric jet model. Favorable results were found in all three cases with good results in the case of the axially symmetric jet model. The relationship between updraft width and maximum vertical velocity is almost linear for smaller updrafts, but deviates from linear for the wider updrafts. It was found that a sensible temperature excess exists in the updrafts at the altitude where measurements were taken (5.0 to 6.2 km).

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Wayne R. Sand
,
William A. Cooper
,
Marcia K. Politovich
, and
Donald L. Veal

Abstract

The characteristics of clouds which have led to airframe icing on an instrumented Beechcraft Super King Air are summarized. The icing encounters occurred at altitudes from 0–8000 m MSL, in summer and winter, in stratiform and cumuliform clouds, and at temperatures from 0 to −30°C. The characteristics of icing encounters in different areas and in different seasons are compared. The fraction of measurements exceeding various threshold values of liquid water content, average liquid water content over a given distance, volume-median droplet diameter, droplet concentration, ice crystal concentration, and potential ice accumulation are given. The effects of these cloud characteristics on aircraft performance were measured by comparing the rate of climb of the aircraft with ice to the rate of climb for the clean aircraft under the same conditions. Most icing encounters led to a reduction in the rate of climb that increased linearly with the path integral of the supercooled liquid water content. The volume-median diameter had little correlation with changes in performance. Some potentially hazardous conditions, which decreased the rate of climb capability of this aircraft by 7–9 m s−1, are also discussed.

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