According to the concept of soil-moisture-balance in Palmer-drought-model,daily drought index(DDI) is defined by available water content(AWC) below level soil. AWC was simulated day by day using daily data of temperature and rainfall.

• 参考帕默尔(Palm er)旱度模式中土壤水分平衡概念；提出以逐日气温和降水资料；逐日滚动模拟土壤有效水分；并以下层土壤有效含水量构建干旱强度动态指数(DD I).