FlexGrid

NOTE: This page is being actively edited right now and the information might be incomplete.

FlexGrid documentation by Jiawei Zhuang (jiaweizhuang@g.harvard.edu)

Overview

FlexGrid is a new functionality in GEOS-Chem v11-02 to unify all metfield I/O routines by HEMCO.

HEMCO's I/O interface and regridding&cropping capability allow users to

• Set up a nested simulation over any custom domains without changing model's source code.
• Explicitly control each meteorological variable in run-time configuration files to perform metfield experiments (an interface resembling GCHP).

FlexGrid idea

In theory, setting up a new nested domain simply requires

• New metfields over that domain
• New regional emission data sets if necessary
• Tunning several domain-dependent or resolution-dependent parameters.

There's no reason that one has to touch the model source code. However, in previous versions, all nested domains were hard-coded so users need to do a lot of tedious coding in order to set up a new domain. The major trouble was metfield I/O, as we assumed that the model grid should exactly match the metfield grid. The solution to this is HEMCO, which has been used to regrid emission data sets at different grids to the same model grid. Now let's just do the reverse: regrid the same metfield data set to different user-specified domains.

FlexGrid implementation plan

The table below shows the implementation plan for FlexGrid:

Stage	Detail	Status
Stage 1: Read metfields by HEMCO	Enable the compile option "MET=flexgrid" to read any NetCDF-format metfields through HEMCO. This unifies "MET=geosfp" and "MET=merra2"	Will be included in v11-02
Stage 2: Implement custom nested simulations	Enable the compile option "NEST=cu" (custom) to allow custom nested simulations.	Will be included in v11-02
Stage 3: Grid-independent GEOS-Chem classic	Unify compile options "GRID=xxx" by moving all grid size parameters and resolution-dependent parameters to run-time configuration files.	No specific plan right now. Need to be traded off against the nested-GCHP development.

FlexGrid for different types of users

Users with different research focuses and different computational resource available can get different benefits from FlexGrid: