气象干旱指数在东北春玉米干旱监测中的改进

利用土壤相对湿度数据和县级春玉米单产数据，在气象干旱指数SWAP（standardized weighted average of precipitation）的基础上，研究我国东北地区春玉米受干旱影响的界限指标，结果表明:SWAP在春玉米播种-出苗期低于-0.9，出苗-拔节期低于-1.0，拔节-抽穗期低于-1.2，抽穗-乳熟期低于-0.7时，土壤相对湿度偏低，即气象干旱一般为中旱时，不利于春玉米生长。以此构建春玉米干旱指数，对比我国东北地区春玉米干旱指数与省级农作物干旱受灾面积的关系，发现两者相关关系显著，尤其在典型干旱年份，两者对应关系更好，说明构建的东北地区春玉米干旱指数能够较好地反映干旱对春玉米的实际影响。利用东北地区县级春玉米单产数据对春玉米干旱指数进行等级划分，划分结果可为东北地区春玉米防旱减灾和安全生产提供参考。

The Spring Maize Drought Index in Northeast China Based on Meteorological Drought Index

Drought is the main disaster which influences spring maize over Northeast China, and spring maize yields are often affected by large regional and sustainable drought seriously. The decreasing effects can be described with meteorological drought index or agriculture drought index. Using the soil relative moisture data and county spring maize yield, as well as meteorological drought index SWAP (standardized weighted average of precipitation), a new spring maize drought index (I_MD) is proposed, which can reflect the decreasing maize yield induced by drought. Using soil moisture data, the spring maize drought limit is firstly researched based on SWAP. Results show in different stages of spring maze growth, SWAP thresholds are different, which are -0.9 for sowing and seeding stage, -1.0 for seeding and elongating stage, -1.2 for elongating and flowering stage, and -0.7 for flowering and maturity of spring maize. In other words, the growth of spring maize can be influenced when SWAP is moderate drought. A new spring maize drought index is researched based SWAP and SWAP limits. And results also show there is a good relationship between spring maize drought index and the provincial crop area affected by drought, especially in drought years. The coefficient between spring maize drought index and the provincial crop area affected by drought is 0.69 in Liaoning, and 0.73 in Jilin, as well as 0.64 in Heilongjiang, which indicates the new spring maize drought index can indicate actual maize drought. Finally, the classification of drought is divided using the county spring maize yields. The drought grades are defined according to the corresponding decrease of spring maize yield, light drought for (3%,5%] decrease, moderate drought for (5%,10%] decrease, severe drought for (10%,20%] decrease, and extreme drought when the spring maize yield decrease is more than 20%. As a result, when light drought, moderate drought, severe drought and extreme drought happens, the spring maize drought index range is (3.2,4.2], (4.2,6.7], (6.7,11.7], and above 11.7. The research could provide effective method for drought prevention and disaster reduction.