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A How-to on Modifying CESM Conditions to Implement Interesting Experiments

Most users of CESM apply it to the modern day for which it is configured right out of the box. This restriction to modern day is primarily enforced as “boundary condition data files” that the model reads at runtime to determine among many things - the land/sea distribution, topography, vegetation distribution, coupling between grids, river directions vectors and various initial data files. Those interested in studying paleo climate (such as me) need to modify these data files in order to get the model running correctly. Here I present an detailed report on the changes that are needed for each model component as well as the software that one needs to do this. I will show how I used these steps to configure the model for my Pliocene time-period experiments. I will also show preliminary reconstruction of boundary conditions for the PMIP4 transient climate simulations of the deglaciation (21-9 kya). I expect that this talk will be of interest to anyone who has wanted to modify either some or all of the various components of the CESM model, as well as to anyone who is interested in learning more about the workings of CESM.