MINISTRY OF AGRICULTURE AND FORESTS
AGENCY HAIL SUPPRESSION

The Republic of Bulgaria has had thirty years of experience in actively combating unfavourable atmospheric conditions.
The Agency Hail Suppression at the Ministry of Agriculture and Forests (MAF) was established on 30 April 1968. Its purpose is to organize and execute active impacts on hailstorm clouds and other adverse meteorological conditions; artificial increase of rainfall amounts and redistribution of rainfalls; and radar measurement of rainfall amounts.
The agency comprises nine operative regional directorates in control of some 187 rocket-launching sites. These cover approximately one fourth of country's cultivated land.
The method currently implemented in Bulgaria is ground launched rockets carrying AgJ, whose structure is similar to that of the ice and the introduced particles serve as ice-forming nuclei. This makes it possible to directly inject ice-forming reagent at precisely the determined seeding place within the cloud. The method is appropriate for both anti-hail prevention, as well as for rainfall stimulation and modification
Our hail suppression agency has broad experience in collecting cloud resource data by region, as well as in carrying out experiments aimed at rainfall stimulation and modification.
Highly qualified meteorologists, engineers and technical staff with experience in impacting work at the Agency.

THE EXECUTIVE AGENCY FOR HAIL SUPPRESSION PROPOSES:

THE PLANNING AND EXECUTING OF A STIMULATED RAINFALL AND HAIL-PREVENTION EXPERIMENT

1. Preliminary research
To undertake active impact operations (stimulated rainfall and hail combating) some preliminary surveying is necessary to determine the cloud resources. It includes the defining of clouds by type and area of distribution, phase structure and aerological sounding data. This information is needed to estimate the cloud responsiveness to impact and the type of active reagent to be used and appropriate methodology to create the impact.

2. Setting up of a system for radar, precipitation observation (hail impact network).
For the purpose of planning and controlling the impact experiment, it is necessary to set up a special radar station to monitor the dynamics and the phase condition of the clouds. The rainfall measuring (hail impact) network is needed to juxtapose radar data with the actual rainfall amounts. The following stages should be considered:

A. Estimation of cloud resources over a given area with a view to stimulating rainfall or combating hail:

a. Synoptic and climatic analysis of the processes of cloud and rain formation over a fixed territory;
b. Studying the aerological and synoptic conditions;
c. Radar observation of clouds to determine their structure and the potential for stimulating rain and preventing hail;
d. Collecting data from the ground rainfall (hail impact) network;
e. Gathering information on the clouds' microphysics.

B. Planning the experiment:

a. Defining the type of experiment (randomized, control area, etc.) and its length to make its estimated effect reliable;
b. Choice of test-predictors to evaluate the experiment;
c. Determining the seeding criteria;
d. Determining the type and dosage of the reagent, the injection tools and the implanting scheme;
e. Choice of statistical testing method to assess experiment results.

3. Supplying and setting up the technical system and equipment for the stimulating rainfall and hail prevention.

4. Securing of specialized software products for the processing of radar data on active impacting adverse atmospheric processes, for fire control and meteorological data analyses.

5. Staff training and assistance in carrying out active impact operations.