A constellation of satellites is now in orbit providing information about terrestrial carbon and water storage and fluxes. These combined observations show that the tropical biosphere has changed significantly in the last 2 decades from the combined effects of climate variability and land use. Large areas of forest have been cleared in both wet and dry forests, increasing the source of carbon to the atmosphere. Concomitantly, tropical fire emissions have declined, at least until 2016, from changes in land‐use practices and rainfall, increasing the net carbon sink. Measurements of carbon stocks and fluxes from disturbance and recovery and of vegetation photosynthesis show significant regional variability of net biosphere exchange and gross primary productivity across the tropics and are tied to seasonal and interannual changes in water fluxes and storage. Comparison of satellite based estimates of evapotranspiration, photosynthesis, and the deuterium content of water vapor with patterns of total water storage and rainfall demonstrate the presence of vegetation‐atmosphere interactions and feedback mechanisms across tropical forests. However, these observations of stocks, fluxes and inferred interactions between them do not point unambiguously to either positive or negative feedbacks in carbon and water exchanges. These ambiguities highlight the need for assimilation of these new measurements with Earth System models for a consistent assessment of process interactions, along with focused field campaigns that integrate ground, aircraft and satellite measurements, to quantify the controlling carbon and water processes and their feedback mechanisms.

中文翻译：

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21世纪热带陆地碳平衡及其与水循环相互作用的卫星观测

现在有一个卫星星座正在运行，提供有关陆地碳，水的存储和通量的信息。这些综合的观察结果表明，在过去的20年中，由于气候变化和土地利用的综合影响，热带生物圈发生了显着变化。湿林和干林都砍伐了大片森林，增加了大气中的碳源。同时，由于土地使用方式和降雨的变化，净碳汇增加，热带火灾的排放量至少在2016年之前有所下降。对扰动和恢复以及植被光合作用的碳储量和通量的测量表明，热带地区净生物圈交换和总初级生产力的区域差异很大，并且与水通量和储量的季节性和年际变化有关。通过卫星估算的蒸散量，光合作用和水蒸气中的氘含量与总储水量和降雨量的模式进行比较，表明存在热带森林之间的植被-大气相互作用和反馈机制。然而，这些对存量，通量和它们之间的推断相互作用的观察并不能明确地指出碳和水交换中的正反馈或负反馈。