亚像元尺度上的积雪粒径和污染物遥感反演研究

Changes of snow grain size and pollutants over snow cover may result in strong fluctuation of snow albedo, subsequently have feedback effects on the climate system and affect the hydrological processes. Focusing on snow grain size and pollutants, the following research would be carried out: 1) exploring the influence of snow grain size and pollutants (black carbon and dust) on bidirectional reflectance of snow, by analyzing measured snow data from the experiments which would be conducted on various snow cover types (snow grain size and pollutants) ; 2) developing a new snow radiative transfer model based on experimental measurements and Asymptotic RadiativeTransfer model (ART), which can simultaneously simulate snow grain, black carbon and dust; 3) on scale of subpixel, coupling the new snow radiative transfer model and Fully Constrained Least Squares-Linear Spectral Mixture Model (FCLS-LSMM, and subsequently developing an intergrated retrieval model including retrievals of snow area proportion, snow grain size , black carton as well as dust; 4) producing the retrieval products of snow area proportion, snow grain size, contents of black carton and dust over north Xinjiang province based on MODIS and MERSI, assessing the accuracy of these products. This project will enhance and improve the methods of quantitative remote sensing of snow, meanwhile provide richer and more reliable inputting data for hydrological and atmospheric models. Our research is also promising.

积雪粒径及积雪污染物的变化会引起积雪反照率的强烈波动，对气候系统产生反馈作用，进而影响到水文过程。专注于积雪粒径和积污染物，本项目拟开展以下方面的研究：1）通过分析不同积雪类型（积雪粒径，积雪污染物）的野外积雪观测资料，探索积雪粒径、积雪污染物（黑碳，尘埃）对积雪双向反射率的影响；2）基于野外观测数据和渐进辐射传输模型（ART）发展一个可同时模拟雪粒径、黑碳和尘埃含量的积雪辐射传输模型；3）在亚像元尺度上，耦合积雪辐射传输模型与全约束最小二乘混合像元分解模型（FCLS-LSMM），构建一个集积雪面积比例、雪粒径、黑碳和尘埃含量反演为一体的遥感积雪参数反演模型；4）基于多光谱影像MODIS和MERSI制备北疆地区一年的积雪面积比例、雪粒径、黑碳和尘埃含量产品，并检验产品精度。本研究将在提高和完善积雪定量遥感方法的同时，为水文和大气模型提供更丰富、更可靠的输入，具有很好的应用前景。

积雪粒径和黑碳的遥感反演是积雪遥感领域的难题。通过分析不同积雪类型（积雪粒径，积雪污染物）的野外积雪观测资料，探索积雪污染物（黑碳，尘埃）对积雪双向反射率的影响，结合渐进辐射传输的模拟的BRDF进行比较，发现了积雪随粒径以及污染物变化时的BRDF变化规律，同时利用结果与渐进辐射传输模型ARTM进行对比，发现了模型模拟方面的不足；在ARTM的基础上发展了针对MODIS影像的积雪粒径和黑碳反演算法-SGSP算法，该算法考虑了积雪粒径的差异，考虑了积雪亚像元造成的影响，可以同时反演积雪粒径和积雪中的黑碳浓度，利用该算法制备了北疆地区2000-2018年的积雪粒径和黑碳产品；利用在我国三大区采集的积雪样本，分析了三大积雪区中积雪中的不溶性光吸收物质（ILAPs- Insoluble light-absorbing particles）的主要成分，研究表明东北地区积雪污染物主要是黑碳，而在北疆和青藏高原积雪中不溶性微粒主要来源是粉尘。