Traditionally, CLM has only output history fields on the model lat-lon grid. CLM3.0, however, has the new capability to output RTM river routing related fields directly on the RTM grid, rather than interpolating them back to the model grid as was the case in CLM2.1 and CLM2.0.
All aspects of history file output are controlled by the files histFldsMod.F90 (Section A.58) and histFileMod.F90 (Section A.57). The histFileMod.F90 contains routines for creating, updating and outputting the history buffer during the course of a model simulation whereas histFldsMod.F90 contains the user interface for defining all the output history fields (on both the model grid and the RTM grid).
In what follows, we provide a discussion of the CLM3.0 history field interface as well as a summary of the user modifications needed to add new history fields to the model output. We discuss the history field interface for both the model grid as well as RTM grid history output. By default, model grid output is always assumed in the history field interface. It is assumed that the user is completely familiar with Fortran 90 pointer concepts and syntax.