基于遥感与VIC模型的干旱区土壤水分时空变化特征
Spatiotemporal Variation of Soil Moisture in Arid Area Based on VIC Land Surface Model and Remote Sensing

大规模、高精度、长时间序列的土壤水分研究对提高干旱区的旱情预警能力、生态环境恢复能力与精准农业发展具有重要的科学指导意义。遥感技术的迅速发展为实现土壤水分动态监测提供了新的手段,但是地表下垫面异质性与天气影响仍是监测中的一大难题,而结合陆面过程模型对土壤水分进行连续性和真实性模拟,能够更精确的研究土壤水分的变化规律。本文以Landsat TM与VIC陆面过程模型为依托,以渭-库绿洲为典型干旱样区,采用地统计、3S技术、数值模拟、土地利用分类相结合的方法,从VIC模式模拟和TVDI遥感监测角度出发,探讨2008~2016年研究区年际与年内土壤水分时空变化规律,分析灌溉面积、农作物需水量及土地利用变化对模型模拟结果的影响,并结合实测数据进行精度验证与对比,主要研究结果如下:(1)渭-库绿洲近10年耕地、盐渍地面积大幅度增加。耕地与盐渍地面积增幅达35%以上,荒地面积相较2009年减少约46%,灌丛面积增幅约15%,研究区土地荒漠化趋势得到逆转,整体生态环境得到改善。(2)利用TVDI土壤水分遥感监测模型较好地揭示了研究区土壤含水量时空变化情况。春季,湿润区靠近绿洲北方区域;夏季TVDI值达到0.5以上;秋季,绿洲内部TVDI值大于绿洲外围TVDI值22.12%,外部含水量具有减少的趋势。(3)内陆干旱区VIC分布式水文模型模拟结果表明,空间上,西南地区土壤含水量低于东北区域;雨季,东北区域含水量高于西南地区,干旱区域集中在西南、西北和南部区域。时间上,盐渍土壤表层含水量高于耕地,每年雨季,灌丛土壤含水量高于其它3种地类,荒地与耕地土壤含水量波动范围较相似。耕地VIC土壤水分模拟值较好地响应了农作物需水量月变化。(4)结合两种模型的时间耦合程度来看,灌丛与盐渍地土壤含水量要比耕地和荒地耦合程度高,干湿变化规律明显,异常年份较少;耕地与荒地土壤含水量耦合程度较低,曲线变化幅度较大,异常年份较多。不同年份野外实测土壤水分与其VIC模拟值的R~2在0.34以上,模拟精度较可靠。本次研究以陆面过程模型精细化模拟的优势为干旱区水盐情景模拟与盐渍化动态预报提供坚实的数据支撑。

Large-scale,long-term sequence and high-precision research on soil moisture has important scientific guiding significance for improving drought early warning ability,ecological environment restoration ability and precision agricultural development.With the development of remote sensing technology and land surface process model,people realize that remote sensing monitoring soil moisture has the advantages of large range and high time efficiency,but the underlying surface heterogeneity and weather impact are the biggest problems in monitoring,combined with land surface processes.For the simulation of soil moisture continuity and authenticity,the combination of remote sensing technology and land surface process model simulation can more accurately study the change pattern of soil moisture in spatiotemporal variation.Based on Landsat TM data and VIC land surface process model,this paper uses Wei-Ku Oasis as a typical drought-like area,using geostatistics,3S technology,numerical simulation,land use classification method,From the perspective of VIC model simulation and TVDI remote sensing monitoring,the spatiotemporal variation of soil moisture in different seasons in the study area from 2008 to 2016 was discussed.Analysis of irrigated area and crop water demand,land use area change impact on simulation results.The accuracy and verification were compared with the measured data.The following were the main research results:(1)In the past ten years,the area of cultivated land and saline land had increased significantly,and rainfall and temperature changes have been flat.Using the land use transfer matrix to analyze the changes in the four land types in the oasis,from 2007 to 2017,the area of cultivated land and saline land had increased by more than 35%,the area of wasteland had decreased by 46% compared with 2009,and the area of shrub land had increased by about 15%.The trend of land desertification in the study area had been reversed and the overall ecological environment had been improved.(2)The TVDI model better reveals the temporal and spatial changes of soil moisture content in the study area.From 2008 to 2016,in spring,the overall TVDI value was below 0.37,the wet area was close to the northern part of the oasis;the summer TVDI value was above 0.5;in autumn,the TVDI value in the oasis was greater than the outer moisture content of the oasis by 22.12%,and the external moisture content had a decreasing trend.(3)From the perspective of space,From January to June,the soil moisture content in the southwestern region was about 11% lower than that in the northeast region;From July to September,the soil moisture content in the northeastern region of the study area was generally higher than 35.21 mm,and the arid region was concentrated in the southwest,northwest and south regions;from October to December,The southwestern region was generally 13% lower than the soil moisture in the northeastern region.From the perspective of space,The surface soil moisture content of saline soil was about 0.06% higher than that of cultivated land.In the rainy season,the soil moisture content of shrub soil was about 0.02% higher than that of the other three types of land.During the dry season,the soil moisture content of wasteland was at a low value of 28.41 mm.In the rainy season,the soil moisture content increased to a high value of about 56.78mm;due to the conversion of a large amount of wasteland into cultivated land,the soil moisture content of the oasis wasteland and the cultivated soil were close to each other,between 28.784 and 53.741 mm.The simulated soil moisture value of cultivated land VIC responds well to the monthly change of crop water requirement(4)Combining the temporal coupling degree of the two models,the soil moisture content of shrubs and saline soils was higher than that of cultivated land and wasteland,and the dry and wet changes were obvious,and the abnormal years were less;the VIC simulation curve of soil moisture content of cultivated land and wasteland had a large variation range and more abnormal years.In the field of soil moisture measured in different years and its VIC simulation value R2 was above 0.34,the simulation accuracy was reliable.In this study,the advantages of refinement simulation of land surface process model provide solid data support for water and salt scenario simulation and salinization dynamic prediction in arid areas.

土壤水分; TVDI模型; VIC陆面过程模型; 土地利用类型;

Soil Moisture; TVDI; VIC-3L model; Land use type;

丁建丽;

S152.7;TP79

224988435K