全国及区域尺度上农业旱灾受灾率分级研究

摘要

旱灾是影响我国农业发展的重要自然灾害，如何定量评价旱灾的致灾程度，对旱灾等级进行科学界定，对于农业防灾减灾工作具有重要的意义。该文提出以农作物旱灾受灾率（Ia ）为分级指标，采用系统聚类法和逐步聚类法为分类方法，拟将农业旱灾划分为5级，分别为无旱（D0）、轻旱（D1）、中旱（D2）、重旱（D3）、特旱（D4），通过判别分析法对分类结果进行验证，以期对全国及区域尺度上的农业旱灾等级标准进行合理地划分。研究结果表明：全国农业旱灾等级划分采用类平均法和重心法划分结果一致，D0为0≤Ia ＜10％，D1为10％≤Ia ＜15％， D2为15％≤Ia ＜20％， D3为20％≤Ia ＜25％、D4时Ia≥25％；在区域尺度上， D0为0≤Ia ＜6％， D1为6％≤Ia ＜13％，D2为13％≤Ia ＜22％，D3为22％≤Ia ＜36％和D4为Ia≥36％。考虑到全国农业旱灾标准的推广性以及未来旱灾可能加重的变化趋势，将全国农作物旱灾受灾率在不同等级的范围提升2％～3％。从实际记录年度旱情来看，两个尺度上的分级结果均比较合理，能很好地解释现有农业旱灾的分级现象，可为今后的农业旱灾应急响应研究和实际工作提供参考。%Drought,affecting the agricultural development,is one of the important natural disasters in our country.How to quantitatively evaluate degree of agro-drought and define its grade scientifically is of great impor-tance for agricultural disaster prevention and mitigation.Based on crop drought disaster rate (Ia )as grading index, and by using clustering methods and stepwise clustering method for classification,agricultural drought is proposed to be divided into 5 levels,respectively,no drought (D0),light drought (D1),moderate drought (D2),severe drought (D3),and extreme drought (D4).By discriminate analysis methods the classification results are validated to get the standard classification of agro-drought disaster category.The results show that national agro-drought clas-sification results are consistent by using average linkage cluster analysis method and centroid cluster method,on the D0 level,the rate of agricultural drought disaster (Ia )ranges from 0 to 10%,D1 is 10% to 15%,D2 is from 15% to 20%,D3 is from 20%to 25%and D4 is more than 25%;On regional scale,D0 is less than 6%,D1 is from 6% to 13%,D2 is 13%to 22%,D3 is 22%to 36%and D4 is more than 36%.Considering promotion and use of the national agricultural drought disaster standard and the future trend of the drought may increase,the scope of the national agricultural drought disaster rate is improved 2%~3%.From the point of actual recorded drought, the classification results of two scales are reasonable,and can well explain the existing agricultural drought classifi-cation phenomenon,which is good for the future agricultural drought emergency response researches and can pro-vide the reference for practical work.