عنوان مقاله [English]
Hail is a natural disaster for all people, especially farmers. Usually in the insurance industry to calculate the risk of hail damage in each area, the frequency of rainfall (in terms of days) and the average damage are used, which is statistically significant. Hail is one of the phenomena connected with thunderstorms that occur in unstable atmospheres with high humidity and in the presence of strong winds and with mechanisms that increase instability, and these conditions are affected by Local topography and climatology of air masses. Therefore, in order to obtain an overview of the spatial and temporal distribution of hail damage on agricultural products in East Azerbaijan province and to investigate the differences between different parts of the region in terms of this type of rainfall It is better to identify and introduce the cause of possible differences between different areas and the conditions under which this rainfall occurred by achieving zoning of vulnerable areas in terms of hail damage. Thus, by considering and emphasizing the strategy of natural risk management program, which is considered as a potential and a very serious role in aggravating and increasing the damage caused by natural disasters in the region, it is possible to predict and deal with hail and lead To control the injuries caused by this phenomenon.
materials and methods
East Azerbaijan is located in northwestern Iran between 36˚47' N and 39˚ 40' N latitudes and between 45˚ 3' E and 48˚ 50' E longitudes. East Azerbaijan with an area of 45261.4 square kilometers is located in the northwestern corner of the Iranian plateau, which has agricultural lands of about 1320 thousand hectares, which includes 7.47 percent of the country's agricultural lands. In this study, to investigate and analyze the losses of the agricultural sector due to hail, the statistics of losses of the Agricultural Insurance Fund for the statistical period (2010-2019) were used. Due to the fact that in many cases when the hail phenomenon occurs, its very small area and the limited number of synoptic stations, the occurrence of this phenomenon can not be seen and recorded. So the area to be recorded includes only a small number of these events. Therefore, in order to assess the damage caused by hail in the study area, the days when hail caused damage were extracted and examined from the statistics of damage caused by the Agricultural Products Insurance Fund. Then, spatial statistics, hot spot index and ARC GIS software were used to identify areas vulnerable to hail.
discussion and Results
According to Table (3), we see that the damage caused by this phenomenon on horticultural products in East Azerbaijan province is an average of 123.5 hectares per year, with Bonab city having an average annual level of 568.1 hectares and Ahar with 491.2 hectares and Tark with 476.2 hectares are in the next ranks. But in terms of damage to crops, it was determined that Qara Aghaj with an annual average of 1143.9 hectares has the highest level of damage and Hashtrood with 826.6 hectares and Ahar with 369.1 hectares are in the next ranks.
In terms of the level of damage to the total crop and horticultural products during the study period, it was found that in the province, on average, about 262 hectares of the province's area under cultivation are damaged annually due to this phenomenon. The highest level of damage is related to Qara Aghaj section with an annual average of 1159.7 hectares, which includes 14.7% of the total hail damage in the study area, and Hashtrood and Ahar with 1057.9 (13.4%) and 860.3 hectares (10.9%, respectively). ) Are in the next ranks. In order to identify areas vulnerable to hail, spatial statistics and spatial autocorrelation techniques were used, and in order to ensure areas with high and low value clusters, the * Gi index (Getis - Ard GE) was used. The results showed that in agriculture, the values of positive spatial correlation are concentrated in parts of the south of the province, which is the most vulnerable area in the study area, the central parts of Charavimaq and Shadian, and in the garden sector, the values of positive spatial correlation in Parts of the northwest and southwest of the province are concentrated, and among these, the most vulnerable area in the study area is the central and Yamchi Marand districts.
The results of this study showed that the highest frequency of damaging hail occurred in May and the lowest frequency occurred in August. The results also showed that about 71% of the harmful hail in the study area occurred in the warm seasons, which coincides with the plant growing season in this area. In the period under review, the rainfall of harmful hail in East Azerbaijan province was on average between 09:00 and 15:00 (G.M.T) more than other hours, and in this 10-year period, the maximum rainfall occurred at 12:00.
In the study of hot spots based on Gi* index, it was found that in agriculture and horticulture, high value amounts (positive spatial autocorrelation) are concentrated in parts of the south and northwest of the province, respectively. Examination of the total damage of agriculture and horticulture showed that high values (positive spatial correlation) are concentrated in parts of the south of the province, and the most vulnerable areas in the study are the central parts of Charavimaq, Shadian and Nazar Kahrizi. On the other hand, a region with less vulnerability in parts of the west of the province, especially the central parts of Osku, Khosrowshahr, Mamqan, Gogan and the suburbs of Azarshahr, corresponds to areas with a spatial distribution pattern with the highest significant negative spatial self-correlation and 99 Percentages (strong-cold-cold cluster) are concentrated. By examining vulnerable areas, we can point to the high area under cultivation in these areas, as well as the impact of local factors such as topography and altitude and external factors, including the entry of hail systems from the west and southwest of the province in its occurrence and intensification.