Physical Interpretation of Results from the HIPLEX-1 Experiment

Abstract

The general characteristics of the clouds that were included in the HIPLEX-1 experiment are reviewed, and the results for the response variables are interpreted in light of other measurements from the instrumented aircraft. In most seeded clouds, the HIPLEX-1 experimental hypothesis corresponded with the observed precipitation development for only the first ?8 min after seeding. The failure to obtain a stronger statistical result is attributed to the inherent inefficiency of the small cumulus congestus selected as experimental units. This inefficiency was only partly due to low ice concentrations; a more significant cause of the low precipitation efficiency was the limited lifetime and low liquid water content of these clouds. Some calculations which indicate that these clouds could not support a rapid enough accretional growth process to lead to precipitation after seeding are discussed. Other reasons for the successes and failures of the experiment are discussed.