Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: Ronald Biondini x
  • All content x
Clear All Modify Search
Ronald Biondini


This paper presents some of the results obtained from a new analysis of the data collected during 1968 and 1970 by EML in the Florida cumulus modification experiment (the “single cloud” experiment).

The most important new element in this analysis is the stratification of the data into categories based on cloud motion. Category 1 days are those displaying significant, relatively uniform cloud motion throughout the day. Category 2 days are those displaying no such motion.

First the rainfall data are analyzed without regard to motion categories, the log-normal model is introduced, and evidence for multiplicative seeding factor is adduced and its value estimated. The data are also analyzed on a pairwise basis.

Next the data are stratified by motion categories and the analysis repeated with categories. It is shown that although a log-normal model can still be applied within categories, there is no basis for assuming a multiplicative seeding factor within categories. It is shown that category 1 clouds respond to seeding in a significantly different manner than do category 2 clouds.

Evidence indicating that seeding tends to promote the merger of clouds is presented.

The lifetimes of those clouds which did not merge are analyzed. Seeding apparently increased the lifetime of these clouds by about 40%. This holds both across and within motion categories. With the exception of a single outlier, the lifetime data can be taken as log-normal.

It is shown that the effects of seeding on rainfall, both within and across motion categories, of non-merging clouds are mainly effects on intensity (average rainfall per unit time) rather than on lifetimes.

The implications of these results to cloud modelers, cloud modification operations, and further statistical analyses are briefly discussed.

An effort is made to identify a cloud-by-cloud seeding effect. A quantity called the “rank indicated seeding effect” is introduced and compared to a quantity called “pair wise seeding effect.” It seems that these quantities behave much more regularly for category 1 clouds than for category 2 clouds.

In an appendix, some properties of the log-normal distribution are presented along with some discussion as to the relevance of these properties to these analyses and those anticipated in the future.

Full access
Ronald Biondini, Joanne Simpson, and William Woodley


The data obtained from the Florida Area Cumulus Experiment in the years 1970–75 are analyzed statistically. Specifically a set of empirically derived predictors for both seeded and unseeded rainfall is identified. First the experiment is briefly described and the data given. The concept of echo motion categories is presented. The responses to be predicted and the variables used as predictors are listed and described and the methods for obtaining the prediction models are given. Next comes a listing of the model equations obtained by those methods, along with some commentary on their possible physical meaning. Examples illustrate the use of some of these prediction models for estimating seeding effects and possible bias in selection of experimental days. A discussion of the echo motion covariate and the basic predictor variables, their histories, rationales and some theoretical indications of their importance completes the main body of the paper.

Full access
William L. Woodley, John A. Flueck, Ronald Biondini, Robert I. Sax, Joanne Simpson, and Abe Gagin

The Florida Area Cumulus Experiment (FACE) is a long-term program to determine the potential of dynamic seeding for increasing convective rainfall over a fixed target area. The first phase of FACE (FACE-1) provided strong indications for increased, seeding induced rainfall. The second phase, FACE-2 (beginning in June 1978 and ending in August 1980), was conducted in an attempt to confirm these indications of a positive seeding effect. The criteria for confirmation in FACE-2 were published in a NOAA Technical Report prior to program commencement. A clarification and sharpening of these confirmatory criteria are discussed in this paper. In addition, a minority position of what is to constitute confirmation in FACE-2 involving the use of linear predictor models also is discussed. This paper was written and accepted for publication before the treatment decisions of FACE-2 were known.

Full access