基于AMSR-E的黄河源区表层土壤水分时空变化

黄河源区生态环境和水文过程对气候变化的响应是该区域研究的热点问题,但相对于其他环境和水文要素而言,大尺度长序列的土壤水分时空分布特征研究不足.本文基于AMSR-E被动微波遥感数据和地面实测数据,首先采用引入Qp模型的双通道反演算法校正AMSR-E土壤水分数据,获得的土壤水分产品(SMD)精度高于官方提供的土壤水分产品(SMo),但其波动范围与实测数据有差异.之后采用逐月回归分析法对SM0进行二次校正,其土壤水分产品(SML)具有更高的精度且变化趋势与实测数据一致.基于SML土壤水分产品,对黄河源区及其5个自然分区表层土壤水分的时空变化特征及其影响因素进行分析.黄河源区年平均表层土壤水分为0.140～0.380 cm3/cm3,在2003-2010年间呈下降趋势,在东南部土壤水分较高的若尔盖丘状高原区、黄南山地区和果洛玉树高原宽谷区土壤水分呈下降趋势,其中若尔盖丘状高原区的下降速率最快,而在西北部土壤水分较低的黄河源宽谷湖盆区和柴达木东缘山区呈增加趋势;春季土壤水分呈下降趋势,夏季呈增加趋势,秋季的波动较大,冬季的变化的不大,其中9月土壤水分增加率和5月减少率最大.土壤水分受降水和植被指数的影响最大,气温表现为在年高温月份与土壤水分呈负相关,在年低温月份呈正相关.研究结果为AMSR-E土壤水分数据的研究与应用提供了依据,有助于深化对区域尺度土壤水分格局及其对气候变化响应的研究,对高原生态环境建设有重大意义.

Spatial and temporal variations of the surface soil moisture in the source region of the Yellow River from 2003 to 2010 based on AMSR-E

[Background] Hydrological processes in the source region of the Yellow River (SRYR) are increasingly attracting local concern,particularly when coupled with a changing climate.Nonetheless,large-scale spatial and temporal variations in soil moisture have received minimal research attention compared to other hydrological variables in the area.[Methods] Based on a two-channel retrieval method with a Qp model through monthly regression analysis and Advanced Microwave Scanning Radiometer-EOS (AMSR-E) soil moisture data,we investigate the spatial and temporal variations of the surface soil moisture and its influencing factors in the SRYR and through five natural zonings in the SRYR during 2003-2010.[Results] Through successive corrections with the dual-channel retrieval algorithm with the Qp model and the monthly regression analysis,the AMSR-E soil moisture shows strong agreement with in situ data in the SRYR.The average annual surface soil moisture in the SRYR is 0.140-0.380 cm3/cm3.There is a decreasing trend in the moisture content in the entire SRYR over the study period (2003-2010).Generally,a decreasing trend occures in the areas with higher initial soil moisture values from 2003 to 2010,while increasing trend in the areas with lower initial soil moisture concentrations over the same period.The soil moisture is highly positively correlated with precipitation (r =0.80,P ＜ 0.01) and the NDVI (r =0.79,P ＜ 0.01) over the entire year.The soil moisture is also negatively correlated with air temperature in months with high temperatures (from April to September) and positively correlated with air temperature in months with low temperatures (from January to March and from October to December).[Conclusions] This paper illustrates that the surface soil moisture of the SRYR has the tendency of drying,and precipitation and vegetation account for the decrease of soil moisture.Results of this paper provide an effective way for AMSR-E official soil moisture products application,would help to understand the hydrological process and its response to climate change,and have a scientific significance for ecological environment construction in Plateau.