Framework for an Earth System Reanalysis – EARTH^(RA)

EARTH^（RA）项目将开发和应用第一个动态一致气候再分析框架，其中数学上严格的、基于伴随的气候数据同化和参数优化将成为耦合地球系统模式（ESM）的一个组成部分。新的EARTH^（RA）框架将克服长期存在的问题，即迄今为止通过参数估计产生的模型偏差阻碍了气候预测的进展，从而推动气候建模，从而通过改进气候预测来开发新的气候变化信息，以支持决策。（1）建立一个新的完全耦合ESM伴随建模和参数估计框架，需要将非线性ESM与海洋、大气和冰冻圈的现场和卫星数据相结合，开创完全耦合地球系统再分析的先河，推进同化技术，以处理耦合气候系统的非线性和混沌性质，并通过推进现代自动微分工具，使严格的数据同化方法得以使用;（2）在一年到十年的时间内，通过将控制理论应用于完全耦合的ESM，进行第一次飞行员观测约束地球系统再分析。该框架将用于该项目，以（1）客观和透明地使完整的地球系统模型（ESM）通过动态一致的数据同化和参数优化（地球系统再分析）与气候观测保持一致，（2）研究伴随的气候敏感性和反馈，从而提高我们对气候系统及其调整过程的理解。该框架将牢固地建立在一个新的伴随地球系统模型的基础上，该模型的原理可以随后被任何建模中心采用。通过这种新的框架，观测信息模型改进将成为模型改进的一个重要组成部分，与经典的前向模型发展是双重/互补的。

The EARTH^(RA) project will develop and apply the first framework for a dynamically consistent climate reanalysis in which mathematically rigorous, adjoint-based climate data assimilation and parameter optimization will become an integral part of coupled Earth System Models (ESM). The new EARTH^(RA) framework will advance climate modeling by overcoming the long-standing problems of model biases through parameter estimation hitherto hampering progress in climate predictions, thereby enabling the development of new climate change information through improved climate predictions needed to support decision-making.The EARTH^(RA) work program will have two major elements: (1) establishment of a novel adjoint modeling and parameter estimation framework for fully coupled ESM, required to combine non-linear ESMs with in situ and satellite data of the ocean, atmosphere and cryosphere, pioneering a fully coupled Earth system reanalysis, advancing assimilation techniques to deal with non-linearities and the chaotic nature of the coupled climate system, and enabling the use of mathematically-rigorous data assimilation approaches by advancing modern automatic differentiation tools; (2) performance of a first pilot observations-constrained Earth system reanalysis through the application of control theory to fully-coupled ESMs over a year to a decade. The framework will be used in this project to (1) objectively and transparently bring full Earth System Models (ESM) into consistency with climate observations through dynamically consistent data assimilation and parameter optimization (Earth system reanalysis), (2) study adjoint climate sensitivities and feedbacks thereby improving our understanding of the climate system and its adjustment processes. The framework will firmly be based on a new adjoint earth system model whose principle can be adopted subsequently by any modeling center. Through this novel framework, observations-informed model improvement will become a firm part of model improvement in a way that is dual/complementary to classical forward model developments.