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Date: 20190627 

Summary

The v1 version of CLUBB left pockets of supersaturation for the microphysics.   To mitigate this, the v2 version of CLUBB does CLUBB's saturation adjustment immediately before microphysics when ipdf_call_placement = ipdf_pre_advance_fields.

CLUBB_v2 includes performance optimizations that may lead to speedups, but also may be vitiated by a performance degradation in the CLUBB interface that was introduced in order to change the position of the saturation adjustment.

CLUBB_v2 also adds new options that may be interest when tuning E3SMv2:

 * CLUBB's gustiness can be enhanced if C_wp2_splat is set to non-zero values.  This may enhance the benefits found with Po-Lun Ma connection of CLUBB's gustiness and surface processes.

 * CLUBB_v2 can now prognose momentum fluxes if l_predict_upwp_vpwp = .true.  This is designed to reduce ocean surface stress in cumulus regions.

The purpose of this section is to summarize what capability is to be added to the E3SM  through this design process. It should be clear what new code will do that the current code does not. Summarizing the primary challenges with respect to software design and implementation is also appropriate for this section. Finally, this statement should contain general statement with regard to what is “success.”

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