基于聚类分析的快速辐射传输计算方法研究

In this proposal, a new approach of fast and high-precision vector radiative transfer method that applicable in the short-wave infrared will be developed to provide support for the retrieval of atmospheric greenhouse gas satellite measurement that already in orbit and planned in the near future. The super high precision requirement is the key to the success of greenhouse gas satellite measurement to further data application, and radiative transfer method is one of the importance of high precision retrieval. The line-by-line calculation to meet the accuracy requirement consume a lot of time and computing resources, and it is difficult to meet the requirement of the retrieval of massive satellite data. Based on the analysis of the sensitivity of atmospheric vertical optical properties to the calculation of radiative transfer, this study will develop a clustering method marked by the profile of atmospheric molecular absorption coefficient to fully consider the impact of atmospheric vertical optical properties on the calculation precision, break through the limitation of traditional correlation k-distribution method that only considers the total column optical depth, to ensuring the calculation accuracy. The fast radiative transfer method will be evaluated by direct comparison with line-by-line calculation and retrieval test of satellite measurement.

项目计划发展一套在短波红外波段适用的快速、高精度矢量辐射传输计算方法，为已在轨运行和未来计划的高精度大气温室气体探测卫星数据反演提供支撑。苛刻的精度需求是温室气体卫星遥感观测成败的关键，辐射传输计算是高精度反演的重要核心之一。满足精度要求的逐线计算需要耗费大量的时间和资源，很难应对当今和未来海量卫星数据反演计算的需求。本研究将在分析大气垂直光学性质对辐射传输计算敏感性的基础上，发展以大气分子吸收系数垂直廓线为标识的聚类分析方法，以充分考虑大气垂直光学性质在辐射传输计算中的影响，突破传统相关k-分布方法仅考虑柱总光学厚度的限制，实现在快速辐射传输计算的同时，保证计算精度。并通过与逐线计算的直接对比和卫星实测数据的反演应用对计算方法进行评估。

本项目研究，揭示了在O2A吸收带，CO2短波红外吸收波段，大气光学性质垂直分布、分子吸收线重叠等对计算精度的定量影响，分析了不同聚类方法对光学厚度廓线聚类的应用效果，通过调研和对比已有的快速辐射传输计算方案，总结了其中的优缺点，并研发了新的计算方案，实现了快速计算，并成功应用于中国碳卫星观测数据的实测反演。研究结果经过测试，计算效率比逐线积分计算平均提升约80倍，快速辐射传输计算方法与逐线积分计算方法进行了对比，总体来讲，光谱采样像元的差异均小于0.1%，满足温室气体遥感观测的精度需求。该算法已经应用于中国碳卫星的反演和科学产品的生产，反演精度达到了1.47ppm的国际先进水平，进一步证实了辐射传输计算方法的准确和可靠性；此外，该计算方法已成功应用于美国OCO-2卫星观测实测数据的反演。基于本项目的研究和支持，共发表论文9篇，其中SCI论文8篇，获批软件著作权1项、实用新型专利1项，申请发明专利1项，研究结果获得2021年度中国环境十大科技进展。