CESM

Overview

This is the start of an interface for assimilating observations into the fully-coupled CESM whole-system model. It makes use of the existing POP (ocean), CLM (land), and CAM (atmosphere) model_mod codes.

Note

See ./doc/setup_guidelines.html for much more information.

We have adopted some terminology to help us keep things straight.

  1. CESM already uses the term ‘fully-coupled’, so we use that in reference to CESM components only. It means that CESM has an active atmosphere and ocean, ignoring other components. In CESM an active atmosphere almost always implies an active land, but that is not necessary for it to be called ‘fully coupled’, and, by itself, is not ‘fully coupled’.

  2. We use the term ‘single-component’ to denote the situation in which the assimilations are performed for ONE active model component. Atmospheric obs directly impact the atmosphere, OR land obs directly impact the land, etc.. Any impact from the atmosphere to the land happens through interaction with the CESM coupler.

  3. We use the term ‘multi-component’ to denote the situation in which the assimilations are performed separately for more than one active model component. Atmospheric obs directly impact the atmosphere AND ocean obs directly impact the ocean, etc.. Any impact from the atmosphere to the ocean happens through interaction with the CESM coupler.

  4. ‘cross-component’ is used to specify the case when observations of one component can directly impact any/all of the other active components without going through the coupler.

Prior to 9 Nov 2015, models/CESM had programs that were an attempt to achieve the cross-component, fully-coupled data assimilation. Since this is being implemented with the Remote Memory Access (RMA) strategy that is not consistent with the current SVN trunk, the files that allow that usage pattern are being removed from the SVN trunk. However, there are scripts in ./shell_scripts which enable the ‘multi-component’ assimilation mode, which does not require a models/CESM/model_mod.f90, since it uses a separate filter for each component (cam-fv, pop, …).

The models/CESM/work directory has nothing of use in it, since there are no programs to interact with a cross-component DART state vector (a DART state that consists of atmosphere and/or ocean and/or land).