沙尘气溶胶三维特征分析及辐射模型改进

Different theories for sand and dust storm characteristic retrieval have been developed, but the precision is limited by aerosol model estimate, cloud identification and other factors. The profile of aerosol and water vapor required by traditional algorithm contains uncertainties, which resulted in low accuracy of dust remote sensing over arid and semi-arid areas. Meanwhile, the mixture of sand and anthropogenic aerosols, the interaction with clouds, will influence the accurate evaluation of radiation and climate effects. ..In this proposal, firstly by combining the CALIPSO lidar data and MODIS aerosol products of optical depth, particle size distribution and vertical column dust amount, the three-dimensional distribution of aerosols is presented. In addition with the cloud layer profile and cloud top/base height, the troposphere elevation is distinguished and the dust transport vertical distribution is resolved. Secondly, based on the AIRS infrared and microwave observations, Atmospheric temperature and humidity profiles is studied as well as the thermal structure, with dust, dusty cloud, clean cloud identified. Simultaneously, effective radius of particles on cloud horizon is retrieved by means of the Rosenfeld & Lensky microphysical schemes, with a temperature versus effective radius (T-re) relationship provided. Possible diminish of cloud cooling effect and decrease of precipitation caused by dust aerosol is studied, which aim to the quantitative study of dust indirect radiative effect. After all, an improved radiation model is established for dust aerosol over arid and semi-arid regions in China, in order to advance the accuracy of dust storm quantitative remote sensing and its climate effect prediction.

沙尘气溶胶的卫星遥感精度依然受到气溶胶模型、云识别不确定性的制约，影响其辐射和气候效应的准确评估。本项目拟基于MODIS得到的气溶胶光学厚度、粒子有效半径、垂直气柱内沙尘总量等物理参数，点-面结合CALIPSO激光雷达提供的气溶胶廓线、各层云顶/云底高度，构建沙尘气溶胶光学特性的三维分布、判别对流层高度、解析沙尘输送高度和层次结构特征；联合AIRS资料获得大气温湿度廓线及热力结构，提取沙尘、沙-云混合、冰/水云的光谱特性；进一步利用Rosenfeld & Lensky 云物理反演方法，分析云滴粒子T-re分布关系，研究沙尘气溶胶对云冷却效应和降水可能产生的抑制作用，定量分析其间接辐射强迫，从而提出适用于中国干旱半干旱区的沙尘气溶胶辐射模型改进和完善方案，为进一步提高沙尘气溶胶定量遥感和气候效应预测精度提供依据。

本项目基于多源遥感资料，研究沙尘气溶胶的三维分布特征及其辐射效应。塔克拉玛干/戈壁沙漠地区地表反射率较大，粒子遥感存在多次散射现象，该地区沙尘气溶胶的物理特性研究成为模型优化中的难点问题。本项目1）通过采用MODIS第1、2通道反射率和第32通道亮温度，将沙尘与云像素点从地表像素点中提取出来；进而采用NDDI指数，将沙尘气溶胶与冰/水云迅速区分开来。实现对亮地表上空沙尘气溶胶的高分辨率遥感(1km*1km)。2）进一步结合AIRS、MODIS大气温湿廓线数据，对沙尘天气大气热力和动力结构进行分析，判别对流层高度、解析沙尘输送高度和层次结构特征。结果表明沙尘气溶胶层出现等温层，高度在600-700hpa，温湿三维图中温度露点差较高、温度较低的窄带，对应沙尘天气发生的冷锋峰面。这一层结结构的提取，为沙尘输送机制的进一步分析提供了有效观测依据。3）基于MODIS气溶胶光学厚度、粒子有效半径等参数，点-面结合CALIPSO激光雷达提供的气溶胶廓线、各层云顶/云底高度，提取沙尘、沙-云混合、冰/水云的垂直分布特征；构建沙尘气溶胶物理特性的三维分布结构；4）联合星载AIRS廓线和地基探空数据，获得整层大气温湿廓线及热力结构，对比Rosenfeld & Lensky 云物理法反演的云滴粒子T-re分布关系，探讨了沙尘气溶胶对云冷却效应和降水可能产生的抑制作用。5）采用气溶胶观测网的CIMEL太阳光度计，分析半干旱区站点的气溶胶光学特征，揭示无云大气条件下气溶胶光学厚度年变化及其随波长变化的特点。分采暖非沙尘期、采暖沙尘期、沙尘非采暖期、非采暖非沙尘期四种类型研究沙尘与人为气溶胶物理特性差异，指出在采暖期，细粒子体积浓度以0.08-0.6μm粒子为主，峰值达到0.03μm3•μm-2，沙尘造成0.05-0.08μm，0.6-4μm粒子浓度显著增加，0.15-0.4μm粒子体积浓度数值偏低。本项目通过提出适用于中国干旱半干旱区的沙尘气溶胶辐射模型改进方案，为进一步提高沙尘气溶胶定量遥感和气候效应预测精度提供依据。