基于修正NDVI时间序列的大区域冬小麦全生育期墒情监测

Soil Moisture Monitoring of Winter Wheat in Whole Growing Period Based on Modified NDVI Time Series

针对遥感墒情监测存在的时空分辨率矛盾,提出利用高时间分辨率的共享遥感数据,将修正归一化植被指数(NDVI)作为墒情指示因子,实现对大区域冬小麦全生育期墒情准实时、半定量化监测的思想。首先,对冬小麦种植区域进行地域划分,依据冬小麦的物候特征进行生育期阶段划分;其次,利用遥感数据计算各地域、各阶段的NDVI,针对各阶段冬小麦的生长情况,进行NDVI的自适应修正。经实测墒情数据和修正NDVI相关分析表明,修正NDVI可以作为农田墒情的指示因子;最后,将监测年的修正NDVI与前三年平均值做距平差值分析,得到与前三年平均值相比,冬小麦墒情的时空分布规律,结果与实际观测值相符。可以预见:如果有较长的时间序列积累,可以得到监测年与常年相比,麦田的墒情时空分布规律。研究结果表明:提出的方法,可以用于大区域冬小麦全生育期墒情的半定量化准实时监测,而且遥感数据容易获得,基本不需要实测数据,计算方便,成本低廉。对冬小麦农田管理与决策具有重要的参考价值。

Aiming at the contradiction between temporal and spatial resolution of soil moisture monitoring,using the modified normalized vegetation index(NDVI) as the indicator of soil moisture,this paper puts forward a new method of real-time and semi-quantitative monitoring of soil moisture during winter wheat growth period by using the shared meteorological remote sensing data with high temporal resolution.First of all,the winter wheat planting area was divided into regions,and the growth stages were also divided according to its phenological characteristics;Secondly,NDVI was calculated by using meteorological remote sensing data,and the NDVI was adjusted adaptively in each stage and region.The correlation analysis between measured soil moisture data and modified NDVI showed that NDVI could be used as an indicator of soil moisture.Finally,the temporal and spatial distribution of soil moisture of winter wheat,through compared with those of previous three year averages,was obtained by analyzing the difference between the modified NDVI and the annual mean value,and the result was in agreement with the actual observations.It is foreseeable that if there is a longer time series to accumulate,the temporal and spatial distribution of soil moisture in the wheat field can be obtained through compared with the perennial year.The results show that the method proposed in this paper can be used to semi-quantify and quasi-real-time monitoring of soil moisture in winter wheat in the whole growth period.Moreover,remote sensing data are easy to obtain,almost no need of measured data,convenient calculation and low cost.So,it has important reference value for winter wheat farmland management and decision-making.