基于土壤水分模拟的干旱动态监测指标及其适用性

Dynamic drought-monitoring index based on soil moisture simulation model and its applicability

根据土壤水分平衡原理,采用Penman-Monteith公式计算可能蒸散,逐日滚动模拟土壤有效水分,提出基于土壤水分(SM)的逐日干旱动态监测指标。通过与《气象干旱等级》国家标准中标准化降水指数(SPI)、相对湿润度指数(MI)和综合气象干旱指数(CI)相比较,分析了SM干旱动态监测指标在广东的适用性特征。结果表明:(1)基于SM统计的干旱频发时段(11月—翌年4月)比少雨时段(10月—翌年3月)滞后1个月,SM指标能够刻画干旱相对于降水年变化的滞后效应和逐渐发展的特征,客观反映广东干旱频率季节变化特征;(2)SM干旱指标自动隐含了降水-蒸发过程的时间累积效应,物理意义清晰,能够刻画干旱发生、发展和结束过程的丰富细节,在对干旱过程发展渐进性、降水敏感性和过程完整性方面,具有较好的应用价值。

According to the principles of soil water balance,Penman-Monteith function was adopted to calculate potential evapotranspiration. The daily soil available moisture was simulated,and the daily dynamic drought-monitoring index was put forward based on soil moisture （SM）. With the comparison of the standardized precipitation index （SPI）,relative moisture index （MI）,and combined meteorological drought index （CI） recommended by the ＇meteorological drought levels of National Standards＇ （GB/T 20481-2006）,the applicability of the daily dynamic drought-monitoring index based on SM in Guangdong was evaluated,and the results showed that the drought season （from November to next April） based on SM lagged one month,compared to rain-less period （from October to next March）. The SM index could describe the lag effect and gradual change characteristics of drought relative to the annual change of precipitation,and objectively reflect the seasonal distribution of drought frequency in Guangdong. The drought index based on SM automatically implied the time cumulative effect of precipitation-evaporation process,and thereby,could describe the start,development,and end of drought process in detail. In terms of progressive development,precipitation sensitivity,and integrity of drought course,the drought index based on SM was of good application value.