基于RTTOV模式的大气二氧化碳反演参数敏感性分析

大气二氧化碳是开展全球气候变化和碳循环研究的关键数据。卫星遥感技术与模式模拟相结合的反演方法已成为获取该数据的重要手段,但模式输入参数本身的误差会对大气二氧化碳反演精度产生影响,须在反演算法设计中加以关注。本文利用RTTOV10快速辐射传输模式模拟Aqua/AIRS红外探测仪17个大气二氧化碳反演通道,计算了这些通道上大气顶出射辐射对温度廓线、臭氧廓线、水汽廓线、地表温度和地表发射率的参数误差的不确定性,并与二氧化碳增加0.5%时造成的不确定性进行对比,分析二氧化碳对上述参数误差的敏感性。结果表明,温度廓线误差是干扰AIRS大气二氧化碳反演的主要因素,其次是臭氧廓线误差,而水汽廓线、地表温度和地表发射率的误差对二氧化碳反演的影响在除去个别通道后可忽略不计。最后,本文以通道为单位,确定了各通道上的高敏感参数、敏感参数和不敏感参数,为二氧化碳反演通道的选择和反演算法的设计提供了参考。

Sensitivity Analysis of Atmospheric Carbon Dioxide Retrieval Parameters Based on RTTOV

As one of the main greenhouse gases, global atmospheric carbon dioxide has increased one third over the past one hundred years, becoming the focus of global warming research. Using satellite remote sensing tech- nology and radiative transfer model to retrieve atmospheric carbon dioxide has become the most important means to obtain the global carbon dioxide concentration data. However, the input parameters of radiative transfer model inevitably carry some errors, which will influence the retrieval accuracy more or less, so this influence must be quantified and considered in the retrieval algorithm. In this paper, the radiances of 17 infrared carbon di- oxide retrieval channels located in 15gm wave band of the Aqua/AIRS infrared detection instrument are simulat- ed by the fast radiative transfer model RTTOV10. The temperature profile, ozone profile, water vapor profile, surface temperature and emissivity are considered as the influence factors. And the sensitivities of the outgoing radiance to the errors of these input parameters are calculated. Then the comparison between these sensitivities and that to 0.5% change of atmospheric carbon dioxide concentration is made. Analysis shows that： temperature profile errors have the biggest influence on carbon dioxide retrieval, and these errors should be less than 0.5k. The total sensitivity of all channels to ozone profile errors are about one third of that to carbon dioxide, making ozone profile errors take the second place. The sensitivities to errors of water vapor profile and surface tempera- ture show the same trend which is only high at channel 738.1 cm and 738.4 cm i. Errors of surface emissivity are negligible at all channels, because the sensitivities due to them are far less than that to carbon dioxide. Final- ly, for each channel, these parameters are divided into three classes which are high sensitive parameters, low sen- sitive parameters and non-sensitive parameters, providing a reference for carbon dioxide retrieval channel selec- tion and algorithm design.