This research aims to test data obtained by level 2 retrieval algorithm of SMOS over land, in order to provide information regarding vegetation and soil moisture over forested areas. Results presented in this paperwere obtained using the last 620 version of the algorithm. The correlation between the new vegetation optical depth (VOD) product and the height of the forest estimated by ICES at GLAS lidar on a global scale is investigated. Over South American and African forests a good correspondence between the two variables is observed, with saturation occurring above about 30 m height. Moreover, the comparison between the VOD and the height of the forest shows good spatial and temporal stability, and the r2 correlation coefficient is within a 0.59–0.69 range. Conversely, discrepancies are observed in some Indonesian islands, particularly New Guinea. Over specific areas, the trends vs. forest height obtained with SMOS VOD are compared with the corresponding trends of AMSR-E VOD. Results are also validated at country-level scale. To this aim, accurate estimates of forest biomass derived from airborne lidar over selected forests of Peru, Columbia and Panama are used. Finally, the soil moisture retrieved over forests is investigated, reporting continental maps for Tropical areas and comparisons with ground measurements in selected forests of the US. Continental maps obtained with the new level 2 V620 algorithm cover almost all forest areas, and show seasonal variations which are dependent on climatic zones. Comparisons between soil moisture retrievals in forests and ground measurements of the US SCAN network produce worseRMSE valueswith respect to lowvegetation areas. Significant improvements however are achieved after averaging among close nodes of the ground network

The northern land biosphere is believed to be the main global sink of CO 2 , but the contribution of Europe is uncertain. While bottom-up estimates and inverse atmospheric transport studies based on atmospheric CO 2 observed in situ or from space by OCO-2 point to a moderate rate of uptake, some other inversions based on remotely sensed atmospheric CO 2 from GOSAT/SCIAMACHY and biomass estimates from passive microwave satellite data point to a large sink of around 1 Gt C/yr. We present results from combining both approaches in a data assimilation framework, inverting a biosphere model against in situ atmospheric CO 2 and passive microwave measurements. When assimilating all observations, we estimate a European carbon sink of 0.303 ± 0.083 Gt C/yr for 2010-2015. The result agrees with other bottom-up studies and atmospheric inversions using in situ CO 2 or OCO-2 observations pointing to potential data problems when using observations from GOSAT or SCIAMACHY to estimate the European CO 2 sink. Supporting Information:• Supporting Information S1Correspondence to: M. Scholze, marko.scholze@nateko.lu.se Citation:Scholze, M., Kaminski, T., Knorr, W., Voßbeck, M., Wu, M., Ferrazzoli, P., et al. (2019). Mean European carbon sink over 2010-2015 estimated by simultaneous assimilation of atmospheric CO 2 , soil moisture, and vegetation optical depth. Geophysical Research Letters, 46, 13,803.

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The synergistic exploitation of L-band active and passive measurements has received increasing interest. In this paper, both theoretical simulations and experimental data are employed to get a deeper insight into the relations between the backscattering coefficient and the emissivity. An active/passive discrete model is used to simulate the backscattering coefficient and the emissivity of bare soil, maize crop of various heights, and deciduous forests of various biomass values. Volumetric soil moisture is varied in a 5-40% range. Simulations confirm the already known effects of soil moisture (whose increase produces a decrease in emissivity e and an increase in backscattering coefficient σ 0 ) and the effects of vegetation growth that yields an increase in both σ 0 and e. Experimental data collected by four airborne campaigns and spaceborne active/passive instruments, together with ground measurements, are also reported. Simulated data are used to investigate the sensitivity of active and passive measurements to soil moisture variations under different vegetation covers, and to estimate the coefficient of a linear relation between backscattering coefficient and emissivity.