Brief summary of bug

There is an implicit assumption in the urban building energy model that building width equals street width. However, this assumption can/should be relaxed and building width can be derived from the morphology dataset.

General bug information

CTSM version you are using: release-clm

Does this bug cause significantly incorrect results in the model's science? Yes for urban (greater than roundoff), No for general climate simulations (same gridcell/regional/global climate).

Configurations affected: All configurations with urban landunits

Details of bug

There is an implicit assumption in the urban building energy model that building width equals street width. However, this assumption can be relaxed and building width can be derived from the Jackson morphology dataset. Specifically, the equations which use H/Ws (building height over street width) should use H/Wb (building height over building width). Building width can be derived from (Ws*froof)/(1-froof), where froof is the roof (building) fraction.
A simulation with the new equations indicate that as expected, for froof=0.5, answers are identical (because H/Ws = H/Wb). Differences in other cases depend on the degree of departure from froof=0.5 and the presence and magnitude of space heating and air conditioning. A full assessment of differences by variable, season, density type, and region using ctsm1.0.dev098 can be found in the attached file. This uses the default CLM5 urban datasets.

CTSM98_BUILDENERGY_Analysis_Pub.xlsx

A similar assessment using release-cesm2.0.1 but with the optional new urban datasets (Oleson and Feddema 2019) can be found in this attached file:

CLM50_BUILDENERGY_Analysis_Pub.xlsx

I have SourceMods for this currently, but can put together a branch. It would be nice to get this into the release branch, in particular for the CESM2 large ensemble runs, since it's not going to affect climate and would make the urban output more useful. Along with the new urban properties data (see PR#591).