Moisture Nudging

[AMLattanzi]

Summary

The nudging of only qv in the bdy region can lead to excessive moisture in the boundary region. This is most prevalent when significant condensation qv --> qc occurs in the bdy region (depletion of qv then leads to more nudging of qv).

Proposed solution

Multiple approaches may be taken to alleviate the aforementioned issue. For example, one could nudge qc --> 0 and qv to the BDY target while introducing a theta source for the removal of qc. However, this approach may lead to super saturated conditions in the BDY region. For such cases, when the super saturated fluid exits the BDY region, significant condensation will occur which introduce large theta and corresponding lateral w gradients.

To avoid a super saturated condition in the BDY region, this PR allows condensation within the boundary region. However, nudging to the target bdy moisture content is done with qv + qc. This approach relies on the theta nudging to effectively undo to the condensation source term in the BDY region and only adds qv when the sum of vapor and cloud water exceeds the BDY target value.

Tests

• BNF + Shoc + WSM6 is stable