沙尘气溶胶影响下的地表长波辐射遥感估算

Accurate surface longwave radiation data is extremely important to researches about modeling of the energy exchange between atmosphere and the earth, also about forecasting of the global ecological environment and climate change. As an important radiation forcing factor, dust aerosol is about half of the total aerosol in the troposphere. For it has complex scattering and absorption mechanism, no operational longwave radiation inversion algorithm are developed by considering the effects of dust aerosol. Based on the radiative transfer theory, also the remote sensing physical mechanism and the mathematical law, we set up a database which including the representative surface longwave radiation and thermal infrared channel radiance and parameters depiction of the properties of dust aerosol，and these data are corresponding to worldwide atmosphere profiles and surface conditions under dust aerosol. By deducing the thermal infrared radiative mechanism of dust aerosol, also the sensitivity and correlation of the parameters are analyzed，and the influences of dust aerosol optical characteristics and atmosphere temperature and humidity on surface longwave radiation and sensor spectral radiance are discussed. On the basis of which the models which are suitable for estimation of surface longwave radiation under dust aerosol sky with remotely sensed data are developed. The final findings can provide accurate and reliable surface longwave radiation data for global meteorological numerical simulation and climate change research.

精准的地表长波辐射数据对模拟地气系统能量交换以及研究全球生态环境和气候变化极其重要。作为重要的辐射强迫因子，沙尘气溶胶几乎占了对流层中气溶胶总量的一半。由于其散射、吸收机制的复杂性，目前还没有考虑沙尘气溶胶影响的业务化运行的长波辐射反演算法。本研究以辐射传输理论为基础，采取遥感物理机理和数学方法相结合的思想，模拟沙尘气溶胶存在时全球范围内不同大气廓线和地表场景条件下的地表长波辐射和传感器热红外通道辐亮度，从气溶胶热红外遥感机理推导入手、开展敏感性和相关性分析，研究沙尘气溶胶的光学特征和温湿度廓线变化对地表长波辐射和传感器光谱辐亮度的影响，构建适用于沙尘气溶胶影响下的长波辐射遥感反演方法，为全球气象数值模拟和气候变化研究提供精确可靠的地表长波辐射数据产品。

精准的地表长波辐射数据对地表、大气层顶模型的建立以及全球生态环境和气象气候的研究极其重要。卫星遥感能够提供空间和时间连续性的地表信息，为分析和定量化地表长波辐射提供新途径。目前已有相关的利用卫星数据估算地表长波辐射的方法，并取得了一定的效果。但大多数关于长波辐射的研究集中于大气下行辐射估算，且多以晴空条件为前提，不同气溶胶类型和含量对大气长波辐射反演的影响鲜为人们所关注。由于气溶胶散射、吸收机制的复杂性和异质性，目前还没有考虑各种气溶胶影响的业务化运行的长波辐射辐射反演算法。课题组在分析了多种气溶胶类型和含量对大气下行辐射强迫和大气出射辐射影响的基础上，提出了量化气溶胶强迫的方法。由于沙尘气溶胶影响长波辐射机制的特殊性，在利用其光学性质和大气水汽含量量化沙尘气溶胶长波强迫作用的基础上，建立了适用于沙尘气溶胶条件下的大气下行辐射估算模型。根据不同性质的气溶胶对地表温度遥感反演的影响，改进了通用分裂窗算法，并借助窄波段与宽波段转换模型，发展了适用于沙尘气溶胶影响下的地表上行长波辐射估算方法。最后，对所构建的模型适用性进行了评价，检验结果表明，本研究可显著提高沙尘气溶胶影响下大气下行辐射和地表上行长波辐射反演精度，减少长波辐射应用中的不确定性。