Variation Characteristics And Risk Zoning Of Main Agro-Meteorological Disasters Of Winter Wheat In The He-Dong Region Of Gansu Province

Agricultural meteorological disasters are the most common agricultural natural disasters caused by adverse meteorological conditions in China.There are many kinds of agricultural meteorological disasters in the He-dong region,during the growth period of winter wheat,it is mainly threatened by natural disasters such as drought,late frost and continuous rain.The agro-meteorological disasters that occur during the winter wheat growth period will directly affect the harvest,which will negatively affect the sustainable development of society and the economy.Based on the meteorological data from 35 grids of the He-dong region of Gansu province from 1962 to 2019,production area data of winter wheat from 1990 to 2013,and social and economic statistics from1990 to 2013 were employed.And used standards for drought,late frost and continuous rain to identify drought events in growth period,late frost after jointing and continuous rain during heading to maturing period of winter wheat in recent 58 years.Analyze the spatial and temporal distribution characteristics of the frequency and intensity of disaster events,and used the natural disaster risk theory to divide the risk of disasters.The main results were listed as follows:(1)In recent 58 years,the drought frequency increased by 0.19,0.04,0.07 and0.11 times per decade,respectively of winter wheat during the complete growth period,early stage,middle stage and late stage in the He-dong region.The average frequency was 1.78 times,0.19 times,0.47 times and 1.14 times respectively.And drought intensity increased by 3.25,0.53,1.47 and 1.50 per decade,respectively of winter wheat during the complete growth period,early stage,middle stage and late stage in the Hedong region.The average intensity was 34.73,2,7.82,and 22.37,respectively.The frequency and intensity of drought increased the most and the frequency and intensity were the highest in the late stage of winter wheat,the frequency and intensity of drought increased the least and the frequency and intensity of were the lowest in the early stage of winter wheat;In terms of spatial variation,the frequency and intensity of drought in all growth period of winter wheat increased from south to north,the low value area of frequency and intensity were distributed in Longnan region,and the high value area were distributed in Longdong region and Zhangxian,Longxi and other places of Longzhong region.The frequency and intensity of drought increased uniformly throughout the region in the complete growth period and each growth period,and the amplitude of rise increased from south to north.The amplitude of rise of frequency and intensity were the highest in Longdong region,and the rising trend of frequency and intensity were the most significant in Longzhong region.(2)The frequency of the total,slight,moderate and severe frost events decreased by 0.24,0.07,0.08 and 0.09 times per decade,respectively after jointing in the He-dong region.The average frequency was 4.91 times,1.66 times,1.37 times and 1.19 times respectively.And the intensity of the total,slight,moderate and severe frost events decreased by 0.34,0.03,0.11 and 0.21 per decade,respectively after jointing in the Hedong region.The average intensity was 5.94,1.10,1.67 and 2.36.The amplitude of decrease of the frequency and intensity of severe frost events was the largest,followed by moderate and slight frost events,and the the frost damage in the He-dong region was dominated by the slight frost events;In terms of spatial variation,the frequency and intensity of frost increased from east to west in the whole region,and the frequency and intensity increased from south to nonth in the Longdong region,the high value area of frequency and intensity were distributed in the high altitude areas of Longnan region and Longzhong region.The frequency and intensity of frost decreased in most of the area in the He-dong region,the frost frequency and frost intensity decreased significantly in Longnan region and the northern areas of the Longdong region.(3)The frequency and the longest duration days of continous rain decreased by0.01 and 0.25 per decade,respectively during heading to maturing period of winter wheat in the He-dong region.The average frequency and the longest duration days were1.88 times and 18.79 d,respectively.The amplitude of decrease of the frequency of continous rain in Longzhong region was the largest,and the amplitude of decrease of the longest duration days of continous rain in Longnan region was the largest;In terms of spatial variation,the frequency and the longest duration days of continous rain during heading to maturing period of winter wheat decreased from southwest to northeast.Longnan region had the highest frequency and the longest duration days.(4)The comprehensive risk of drought in the complete growth period and each growth period increased from south to north in the He-dong region,the low-risk areas of drought were located in Longnan region,the high risk areas of drought mainly were located in Longdong and Longzhong region.The area of high risk of drought was the largest in Longdong region;The comprehensive risk of late frost decreased from southwest to northeast in the He-dong region,high-risk areas were mainly distributed in high-altitude areas in the western part of the Hedong region.The low-risk areas of late frost were located in the areas that altitude is shorter of shallow mountainous region in Longnan region,the most areas of Longdong region and the eastern and southern areas of Longzhong region;The comprehensive risk of continous rain during heading to maturing period of winter wheat decreased from southwest to northeast in the Hedong region,the low-risk areas of continous rain were located in the northern area of Longdong region.Most of the areas of Longnan region belonged to the high risk area;The comprehensive risk of agricultural meteorological disasters of winter wheat increased from south to north in the He-dong region,the low-risk areas of meteorological disasters were located in Longnan region and the southern area of Longzhong region,the high risk areas were located in the Longdong region,the most areas of Longzhong region and the northwest area of Zhouqu and Danchang.