The list of supported resolutions depends on the CESM release version. "f10_f10_musgs" is one of the coarsest resolutions with cells that are 10 degrees in latitude and 15 degrees in longitude. To get a list of resolutions you can use the "query_config" tool with "--grids" to list all the possible supported resolutions. Note, that CTSM datasets are not provided for every one of those resolutions however. And we don't have a 27 km resolution option available out of the box. As a matter of fact you are likely going to need to a create surface dataset if you need to run at something near that resolution. The CTSM User's Guide talks about how to create surface datasets. A resolution that would be close to what you want is the quarter degree resolution (for example f02_g17). But, most likely you will need to create surface datasets for it.
