Crop Damage: The Hail Size Factor

Abstract

Between 1986 and 1992 a research project was developed and carried out on hail climatology and the economic repercussions of hail on agriculture in León (northwestern Spain). A target area with an extent of 6825 km2 was defined, within which a network of meteorological observers was established at an average density of 1 per 17 km2. A network of 250 hailpads installed in a grid formation was also laid out over an area of 1000 km2 inside the target area. The frequent occurrence of hailfalls?122 hail days over seven consecutive summers?provided a detailed database and allowed several climatological studies to be made. Crop damage was also closely monitored and quantified. Barley and wheat were selected as crops on which to base an analysis of the relationship between hailfall characteristics and crop damage. As the resistance of plants to hailstones is held to vary according to their physiological state, four different stages of plant growth were defined, beginning with the formation of grain heads. An important conclusion was drawn: the dispersion of percentages of damage always covers the possible variations in resistance caused by the physiological state of the plants. As a result, using only minimal information about hailfall characteristics?namely, the initial reports of observers regarding hailstone size?a working statistical model has successfully been constructed to predict losses to barley and wheat, using data provided by the León hail project.