Comparison of Cloud Tower and Updraft Radii with their Internal Temperature Excesses Relative to their Environments

William L Woodley, Eyal Amitai, Daniel Rosenfeld


Measurements of in-cloud temperature using reverse-flow thermometry were made in and around vigorous Thai supercooled convective clouds on 10 days in April and May 1993. Cloud vs. environment temperature differences were derived from these data and the differences were correlated with cloud and updraft radii at the level (6.5 km) of cloud penetration. This was done as function of whether the clouds were isolated, growing in a group of comparably-sized clouds, or growing as "feeders" to cumulonimbus clouds. Positive correlations were noted in all instances, ranging from a minimum of 0.11 to a maximum of 0.48. The correlations were greatest for the comparisons of the temperature differences with updraft breadth. It was noted further that, for a given tower size or updraft width, the temperature differences were largest for clouds growing as feeders to cumulonimbus clouds. The implications of these findings to the design and evaluation of cloud seeding experiments are discussed. This work was conducted under a contract with the Bureau of Reclamation part of a program sponsored by the U.S. agency for International Development to upgrade Thailand’s weather modification capability.

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