土壤水分是作物生长、地一气水热交换及全球水循环过程中的关键变量,对于旱情监测、水文陆面过程及气候变化的研究具有重要的意义.被动微波遥感凭借对于土壤水分的敏感性已经成为监测土壤水分的主要手段.研究中针对吉林省农田下垫面,利用土壤水分传感器网络监测数据,开展了SMAP(Soil Moisture and Active and Passive)和SMOS(Soil Moisture and Ocean Salinity)被动微波土壤水分产品的真实性检验研究,得出了以下结论:①与实测数据相比较,SMOS L3(升降轨)和SMAP L 3被动微波土壤水分产品存在低估现象,伴随降雨事件会出现高于实测土壤水分的情况;两种被动微波土壤水分产品的无偏均方根误差(unRMSE)都大于0.07 m~3/m~3,但SMAP L3被动微波土壤水分产品数据的ubRMSE略低,为0.078 m~3/m~3;②由于L波段的感应深度要浅于传感器的探测深度5 cm,降雨后土壤表层的变干现象导致土壤水分的垂直不均匀性,这是SMOS和SMAP被动微波土壤水分产品低估土壤水分的原因之一;③SMOS与SMAP亮温分布范围对比结果表明:由于电磁射频干扰(RFI)的影响,RFI对于SMOS的影响更为严重,这或许是SMOS土壤水分产品的RMSE高于SMAP被动微波土壤水分产品的原因.
英文摘要:
Soil moisture is a key variable in the process of crop growth,ground-air water heat exchange and global water cycle, which plays an important role in drought monitoring, hydrological land surface processes and climate change. Passive microwave remote sensing has become the main means of monitoring soil moisture with the sensitivity to soil moisture.In this study, the authenticity test of SMAP(Soil Moisture and Active and Passive) and SMOS(Soil Moisture and Ocean Salinity) passive microwave soil moisture products using the soil moisture sensor network monitoring data carried out against the underlying surface of farmlands in Jilin Province was carried out.The following conclusions were obtained: (1 )Compared with the in situ measured data,SMOS L3(ascending and descending overpasses) and SMAP L3 passive microwave soil moisture products generally underestimated the ground data,but With the occurrence of rainfall events,there will be the phenomenon which is the value of soil moisture products is higher than the in situ data; although the unbiased root mean square error (unRMSE) of the two soil moisture products was greater than 0.07 m~3/m~3,the unRMSE of SMAP passive microwave soil moisture product data which was 0.078 m~3/m~3 was slightly lower; (2)Since the depth of induction of the L-band is lighter than the depth of detection of the sensor(5cm),and the dryness of the soil surface after rainfall causes the vertical inhomogeneity of soil moisture,which is one of the reasons why SMOS and SMAP passive microwave soil moisture products underestimate soil moisture; (3)SMOS has a higher value than the range of SMAP brightness temperature,which may be caused by radio frequency interference (RFI),which makes the error of soil moisture Retrieval and affects the validation accuracy.The comparison of bright temperature distribution of SMOS and SMAP shows that the effect of RFI on SMOS is more serious due to the influence of electromagnetic radio frequency interference (RFI), which may be the reason why the RMSE of soil moisture product of SMOS is higher than that of passive microwave soil moisture product of SMAP.