A reanalysis is a physically consistent set of optimally merged simulated model states and historical observational data, using data assimilation. High computational costs for modeled processes and assimilation algorithms has led to Earth system specific reanalysis products for the atmosphere, the ocean and the land separately. Recent developments include the advanced uncertainty quantification and the generation of biogeochemical reanalysis for land and ocean. Here, we review atmospheric and oceanic reanalyzes, and more in detail biogeochemical ocean and terrestrial reanalyzes. In particular, we identify land surface, hydrologic and carbon cycle reanalyzes which are nowadays produced in targeted projects for very specific purposes. Although a future joint reanalysis of land surface, hydrologic, and carbon processes represents an analysis of important ecosystem variables, biotic ecosystem variables are assimilated only to a very limited extent. Continuous data sets of ecosystem variables are needed to explore biotic-abiotic interactions and the response of ecosystems to global change. Based on the review of existing achievements, we identify five major steps required to develop terrestrial ecosystem reanalysis to deliver continuous data streams on ecosystem dynamics.

中文翻译：

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地球系统科学中的再分析：走向陆地生态系统再分析

再分析是一组物理上一致的最佳合并模拟模型状态和历史观测数据，使用数据同化。建模过程和同化算法的高计算成本导致了地球系统特定的大气、海洋和陆地再分析产品。最近的发展包括高级不确定性量化和陆地和海洋生物地球化学再分析的生成。在这里，我们回顾了大气和海洋再分析，以及更详细的生物地球化学海洋和陆地再分析。特别是，我们确定了现在在目标项目中出于非常特定目的而产生的地表、水文和碳循环重新分析。尽管未来对地表、水文、和碳过程代表对重要生态系统变量的分析，生物生态系统变量仅在非常有限的程度上被同化。需要生态系统变量的连续数据集来探索生物-非生物相互作用以及生态系统对全球变化的响应。基于对现有成就的审查，我们确定了开发陆地生态系统再分析以提供有关生态系统动态的连续数据流所需的五个主要步骤。