遥感颗粒物质浓度反演中的湿度影响和参数化订正研究

Compared with a decade of scientific focus on global climate change using satellite data, remote sensing is still one of the useful methods to develop in local air quality monitoring.Aerosol optical depth (AOD) derived from satellite observation and ground-level particle matters（PM）are reflecting different physical properties of aerosol.The relation between them was intrinsic but varies with weather conditions and pollution transport patterns.Increasing relative humidity(RH) may lead to dramatic changes in aerosol's mass concentration and optical properties. An empirical hygroscopic growing factor, as the ratio of the wet and dry aerosol extinction coefficient, was adopted usually in China.Considered about studies on uncertainties of humidity between aerosol optical properties and PM are limited in China, the project proposes to build parameterized model to decrease uncertainty of relative humidity and increase the PM retrieve precision using AOD processed by remotely sensed data. On the basis of evaluation and comparison of empirical RH correction methods, Field Measurements with spaceborne sensor and ground instruments will be setup. By collecting and analyzing test data, the project will illustrate the mechanism between PM and AOD under air pollution complex situation over eastern China, and further to develop a parameterized correction model using remotely sensed data and online PM data. By fulfilling the objects of study, a parameterized model for relative humidity(RH) correction can be used effectively for retrieving PM from remotely satellite data in eastern China.

湿度因子是导致大气颗粒物消光特性和质量浓度关联机制不确定性的重要环境变量之一，现有湿度订正通常采用经验公式或拟合公式来实现。针对我国此方面研究的不足，考查现有湿度订正方法的适用性和不足，通过颗粒物组分分析和混合状态模拟，分析复合大气污染条件下特征化合物在不同混合状态下的水溶性质及光学性质的变化，设计并实施晴空下气溶胶吸湿性场外立体观测实验，收集典型季节和污染输送背景下的近地颗粒物物理、光学特性的实验数据和高分遥感AOD产品，采用多元回归和最大熵等方法，实现影响因子的优化组合，构建具备物理和实验观测支持的晴空下遥感颗粒物吸湿增长参数化校正模型。课题将从理论和场外观测两个层面分析不同组分条件下光学性质与颗粒物质浓度的变化规律，明确不同季节和污染来源条件下，湿度因子对于遥感颗粒物质浓度的定量化影响，课题的实施有助于建立我国典型地区本地化的湿度订正方法，有助于提高遥感近地颗粒物质浓度反演的精度。

颗粒物的吸湿性是联系颗粒物物理、化学和光学参数的桥梁纽带，也是气溶胶基本光学性质的决定性参数之一。湿度因子是导致大气颗粒物消光特性和质量浓度关联机制不确定性的重要环境变量。本项目针对现有颗粒物质浓度遥感反演湿度订正本地化工作的不足，设计并实施了光学、颗粒物质浓度等指标在内的多种地基设备同步观测试验，收集典型季节和污染输送背景下的近地颗粒物物理、光学特性的实验数据和高分遥感AOD产品。项目完成了不同尺度地基空基观测数据源的交叉比对和气溶胶吸湿增长特性分析。项目评价了新版MODIS C006 3km和10km气溶胶产品的精度，并选择中国东部和西部代表性地区开展遥感颗粒物反演的湿度影响订正，评估了湿度因子对于遥感颗粒物质浓度的不确定性影响。综合外场观测和在线观测资料，基于Mie散射理论和吸湿增长模型，定量化给出了研究区平均质量消光效率的吸湿增长因子，分别按照海岛型、沿海型、内陆城市型、内陆公园型四类给出了研究区平均质量消光效率，为我国东部长三角地区遥感颗粒物质浓度反演过程中湿度影响因子的订正提供定量化参考。本项目研究工作全部按照原有计划完成，项目支持发表相关论文5篇(4篇已发表，1篇审稿中)，培养研究生2名。课题的完成为我国长三角典型地区遥感颗粒物质浓度反演提供了本地化的湿度订正方法。相关研究成果并已应用于2016年二十国集团领导人峰会（G20）环境空气质量保障工作。