Satellite passive microwave observations from 1.4 to 36 GHz already showed sensitivity to vegetation parameters, primarily through the calculations of the Vegetation Optical Depth (VOD) at individual window frequencies, separately. Here we evaluate the synergy of this frequency range for vegetation characterization, through the estimation of two vegetation parameters, its foliage and the photosynthesis activity as described by the Normalized Difference Vegetation Index (NDVI), and its woody components and carbon stock as described by the Above Ground Carbon (AGC), using different combinations of channels in the considered frequency range. Neural network retrievals are trained on these two vegetation parameters (NDVI and AGC), for several microwave channel combinations, including the future Copernicus Imaging Microwave Radiometer (CIMR) that will observe simultaneously in window channels from 1.4 to 36 GHz, for the first time. This methodology avoids the use of any assumptions in the complex interaction between the surface (vegetation and soil) and the radiation, as well as any ancillary observations, to propose a genuine and objective evaluation of the information content of the passive microwave frequencies for vegetation characterization. Our analysis quantifies the synergy of the microwave frequencies from 1.4 to 36 GHz, and shows the expected potential of the CIMR instrument for the monitoring of vegetation parameters in tropical environments, as compared to current instruments. It also confirms that the 1.4 GHz observations have a high sensitivity to AGC, as compared to the other single frequencies up to 36 GHz, at least under tropical environments.

1.4至36 GHz的卫星无源微波观测已经显示出对植被参数的敏感性，这主要是通过分别计算各个窗口频率下的植被光学深度（VOD）来实现的。在这里，我们通过估算两个植被参数（如归一化植被指数（NDVI）所述的其叶子和光合作用活性）以及如以下所述的其木质成分和碳储量，评估了该频率范围对植被特征的协同作用。高于地面碳（AGC），在考虑的频率范围内使用不同的通道组合。针对这两种微波参数组合，对这两个植被参数（NDVI和AGC）进行了神经网络检索训练，包括未来的哥白尼成像微波辐射计（CIMR），它将首次在1.4至36 GHz的窗口通道中同时进行观测。这种方法避免了在表面（植被和土壤）与辐射之间的复杂相互作用中使用任何假设，也避免了任何辅助观测，从而对植被特征进行了无源微波频率信息内容的真实客观评估。我们的分析量化了1.4至36 GHz微波频率的协同作用，并显示了与当前仪器相比，CIMR仪器在热带环境中监测植被参数的预期潜力。这也证实了1.4 GHz观测对AGC具有很高的灵敏度，