Knowledge Resource Center for Ecological Environment in Arid Area
| 机载L波段微波辐射计数据反演干旱区土壤水分的 不确定性研究 | |
| 其他题名 | Uncertainty Study of Soil Moisture Retrieval from Airborne L-Band Microwave Radiometer in Arid Region |
| 王定文 | |
| 出版年 | 2016 |
| 学位类型 | 硕士 |
| 导师 | 黄春林 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 土壤水分是水文、气候及农业学等模型应用中的一个关键变量；其时空分布对全球及区域尺度的水文循环、陆气交互等过程起到一定的作用。土壤水分是影响干旱区生态环境的重要因素，也是干旱区植物生存的必需条件。L波段微波因其波长较长、穿透能力强，对土壤水分敏感而成为被动微波遥感反演土壤水分的最佳波段。微波穿透深度因地表覆盖、土壤质地、土壤水分等条件的不同而存在差异性。然而，大多数研究在L波段微波反演土壤水分的过程中，并没有考虑微波穿透深度的影响。本文基于干旱区气象站的观测数据，分析L波段微波穿透深度对不同土壤层的水分、温度、发射率及亮度温度的影响；并结合双极化（H/V）的L波段微波辐射计PLMR（the Polarimetric L-band Multi-beam Radiometer）数据，通过反演气象站点的土壤水分，以分析L波段在干旱区的穿透特性及其对土壤水分反演精度的影响。具体包括以下内容：（1）通过黑河中游三个干旱站点2012年6月8日~28日的土壤水分和土壤温度观测数据，利用L波段微波辐射辐射模型L-MEB（the L-band Microwave Emission of the Biosphere）进行不同土壤层的发射率及亮度温度的模拟，并利用微波穿透深度公式计算出对应时刻的穿透深度；利用土壤水分、土壤温度和亮温等参数，分析L波段的穿透特性。（2）由于机载辐射计PLMR数据受到射频干扰RFI（Radio Frequency Interference）和飞行状态的影响，使得某些时段数据存在较大的误差，无法准确反映地表信息。因此，采用了两种方法对原始亮度温度数据进行处理，并利用洗牌复形演化算法SCE-UA（Shuffled Complex Evolution Algorithm-Univerisity of Arizona）进行土壤水分的反演，分析观测数据的不确定性对土壤水分反演结果的影响，选择适合的观测数据处理方法，减少观测误差。（3）采用筛选出的PLMR数据，并结合穿透深度处土壤层的水分、土壤有效温度，利用优化算法进行粗糙度及其他半经验型参数的标定，以减少模型误差。再将三种双层土壤有效温度模型，用于土壤水分的反演中，以分析土壤有效温度对微波辐射的影响。（4）在L-MEB、土壤有效温度模型和反演分析的基础上，结合气象站土壤水分和土壤温度、机载PLMR数据，采用SCE-UA优化算法，进行土壤水分等参数的反演，并利用气象站观测数据验证反演结果。通过验证数据，分析L波段在干旱区的穿透深度及其对土壤水分反演精度的影响。通过研究发现，L波段在干旱区的穿透深度范围在8~24cm之间；机载PLMR亮温数据和土壤有效温度对土壤水分反演的影响较大；不同地区的穿透深度处土壤水分的反演结果不同；土壤水分反演的结果与表层土壤水分最接近，其次是穿透深度层的土壤水分；利用L波段微波可进行穿透深度层土壤水分的反演。 |
| 英文摘要 | Soil moisture is a key variable of hydrology, climate and agriculture. Acquiring the spatial and temporal distribution of soil moisture accurately is critical to the studies of hydrological cycle and land-atmosphere interaction not only in global scale but regional scale. Nevertheless, soil moisture is an important factor which affects ecological environment, i.e. vegetation growing in arid region. Due to its penetrating capacity and sensitivity, L-band is the most promising wavelength in the study of passive microwave remote sensing of soil moisture. However, since the penetration depth is depending on land cover, soil texture, soil moisture/soil temperature profiles which finally conserved in the dielectric profile, the quantity research of the penetration depth has not been fully considered in the current L-band soil moisture retrieval algorisms.In this thesis, we evaluate the impact of the penetration depth based on the field observations collected in several weather stations located arid region as well as the Polarimetric L-band Multi-beam Radiometer-PLMR’s data. We analyzes the penetration characteristics at L-band under arid conditions and estimate its possible influence on soil moisture retrieval accuracy. The main steps are:1) A emissivity and brightness temperature simulation with the L-MEB model( the L-band Microwave Emission of the Biosphere) using the soil moisture and temperature observation data of three weather stations at Heihe middle rivers from the June 8 to 28, 2012. Then, the penetration depth time-series is calculated with the simulation outputs.2) A quality control of the airborne radiometer PLMR’s data which is partly polluted by RFI( Radio Frequency Interference) and flight status. To avoid this problem, we processes the original brightness temperature data in two methods. Meanwhile, we estimate the effect of observation’s uncertainty on soil moisture retrieval by inversing the soil moisture with SCE-UA(Shuffled Complex Evolution Algorithm-Univerisity of Arizona).3) To reduce the model error, an optimization algorithm is involved for calibrating the roughness and other semi-empirical parameters with the conception of the penetration depth and PLMR’s data. Besides, three two-layer soil effective temperature(Teff) models are adopted to compare the relationship between the penetration depth and Teff models in the SCE-UA inversion analysis.4) An analysis the impact of L-band microwave on the penetration depth in arid region on soil moisture retrieval accuracy is achieved by synthesizing the L-MEB model, Teff models and inversion analysis combining with the observations.The main conclusions are: the penetration depth at L-band is in the range of 8cm to 24cm. The airborne radiometer PLMR’s data quality and soil effective temperature models are vital to the soil moisture retrieval. The inversion results are varying with the penetration depth in arid region. Basically, they are closest to the surface soil moisture, but closer to the penetration depth layer’s soil moisture. L-band microwave is capable of detecting the soil moisture at the penetration depth. However, these results are restricted by the single site field observation and lacks of qualified PLMR’s data. Key words: Soil moisture; Penetration depth; Arid regions; L-MEB; Soil effective temperature |
| 中文关键词 | 土壤水分 ; 穿透深度 ; 干旱区 ; L-MEB ; 土壤有效温度 |
| 英文关键词 | Soil moisture Penetration depth Arid regions L-MEB Soil effective temperature |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 地图学与地理信息系统 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287702 |
| 推荐引用方式 GB/T 7714 | 王定文. 机载L波段微波辐射计数据反演干旱区土壤水分的 不确定性研究[D]. 中国科学院大学,2016. |
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