engleski

Preliminary statistical analysis of hail characteristics parameters measured with hailpads in the hail-protected western part of Croatia

In the continental part of Croatia operational hail suppression has been conducted for more than 30 years. The current protected area is 24, 100 km2 in size and has 528 hail suppression stations that are managed with 8 weather radar centres. During 2001, hailpads were installed on all hail suppression stations, and a hailpad polygon was established in 2002. The polygon measuring 30 x 20 km (with 150 hailpads) was located in the middle of the western part of the hail-protected area, where the hail suppression system could work without limitations. The larger part of this western area is located close to the state border (with Slovenia, Hungary and Bosnia and Herzegovina), and also near the hail-unprotected part of Croatia. Because of the ban on launching rockets across the state borders, hailbearing Cb clouds that are spreading from the west towards Croatia, enter the hail protected border area not seeded. After crossing the borders, hail suppression stations begin with seeding, but because of a short time interval, the seeding nuclei are not completely effective in clouds in the border area. In this paper data collected from hailpad polygon are statistically compared with the data collected from hailpads in this border area in the period 2001 to 2003. Four parameters are used in the analysis – the average diameter of hailstone, the number of classes, hailstone mass and kinetic energy. The results of the linear discriminant analysis show that there is a significant difference between the data from the border area and the data from the polygon area. The t-test shows a significant decrease of average values of all parameters regarding the border area.

hail; hailpad polygon; kinetic energy; discriminant analysis

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