The use of 2-D imagery to classify the precipitation mechanism in West Texas convective clouds

The availability of water is a necessary ingredient to maintain a high level of agricultural production on the Texas South Plains. Since 1975 efforts have been directed at determining the feasibility of altering the natural precipitation process to increase areal rainfall. A prerequisite of the desired goal is knowledge of the precipitation-forming mechanisms that operate in West Texas convective clouds.

Four clouds sampled during a 1980 field project have been selected for detailed analyses. Emphasis has been placed on data from a Particle Measuring Systems 2-D-C optical array spectrometer probe used to monitor the development of cloud particles. Hydrometeor size, shape, and habit (if frozen) serve to describe cloud microstructure and to define the stage of the precipitation process.

The results indicate that the first precipitation-sized particles are formed by the warm rain process. As the turret matures the development of an ice phase leads to cold rain precipitation. Also, three critical elements of successful cloud modification have been defined: the environmental conditions favorable for effective cloud seeding, an estimate of the minimum time liquid water was available at the sampling level, and the method of cloud treatment.