短波红外CO2反演过程约束研究及初步反演结果

短波红外通道卫星CO2遥感是近年国际研究热点。首先,开展了卫星观测对气溶胶及大气温度的敏感性研究;其次,针对基于最优化理论的非线性迭代反演方法反演过程中的不收敛问题,提出了修正的阻尼牛顿方法(MDNM),并利用模拟数据评估了MDNM方法的有效性;最后,利用GOSAT卫星数据反演CO2的垂直混合比浓度,并与地基TCCON站点数进行比对。研究结果表明:短波近红外CO2卫星遥感受气溶胶散射及温度影响明显;通过地基比对初步验证了MDNM具有良好的精度,两者的相关性R2达到了0.729。

CO2 retrieval and preliminary retrieval results from space-based observations in shortwave infrared band

CO₂ is a primary greenhouse gas in the atmosphere and many scientific missions from all over the world are focused on space-based remote sensing of CO₂ using shortwave infrared technique. We present an improved method to retrieve CO₂ column abundance from space-based observations in a shortwave infrared band.We analyze the sensitivities of CO₂ observations to aerosol scattering and atmospheric temperature profiling using the forward model. We also evaluate the reduced accuracy of CO₂ retrieval caused by aerosol scattering and 1K random error of temperature profiles. We propose a Modified Damped Newton Method (MDNM) for CO₂ retrieval and present the retrieval samples to evaluate the performance of the proposed algorithm.Sensitivity studies show that the influence of aerosol scattering and temperature on CO₂ remote sensing and scattering can cause a misestimate of up to 13.2 ppm of CO₂ concentration. We retrieve the CO₂ column abundance from GOSAT L1B data using MDNM method, and the results are compared with ground-based measurements from Total Carbon Column Observing Network (TCCON). The correlation coefficient R-square between the retrieved results and TCCON measurements is 0.729. Sensitivity studies show that aerosol scattering can cause a significant error in CO₂ retrieval. A comparison between satellite retrievals and ground-based measurements shows good agreement. The proposed MDNM method is preliminarily proven to accurate.