The TKE-EDMF PBL scheme and saSAS cumulus scheme updates for P8C plus a bug fix for the Thompson scheme

[ChunxiZhang-NOAA]

Description

This is the updates for P8C. Overall features for the TKE-EDMF and the saSAS updates are:

The first updates:

• From the 3-km RRFS experiments, the current TKE-EDMF PBL scheme tends to overgrow PBL especially during late afternoon, producing unrealistic widespread popcorn-like precipitation. To reduce the PBL overgrowth, the virtual potential temperature at top of the surface layer rather than that at the model first layer is used as near surface virtual potential temperature in the bulk-Richardson number computation.
• The current TKE-EDMF PBL scheme tends to overmix moisture and hydrometeors. To reduce the overmixing, the entrainment rates for moisture and hydrometeors as well as tracers are increased by about 30%.
• The 3-km RRFS experiments showed that the GFS shallow cumulus convection scheme produced unrealistic light rain. To suppress the unrealistic light rain, the rain conversion rate in the shallow cumulus convection decreases with decreasing grid size for grid sizes less than 9-km.
• In the scale-aware mass flux formulation, the constant value of 0.03 for the updraft fraction was replaced with the parameterized updraft fraction.
• The updated PBL and convection schemes yield slightly improved 500mb height AC.
• Compared to GFSv16 convection schemes, the updated cumulus convection schemes tended to reduce the TC intensity in

The second updates:

• HAFS as well as in GFS, increasing the negative TC intensity biases. In the second update, this underestimated TC intensity issue was addressed.

Bug fix in sL sedimentation of graupel related to updating the graupel terminal velocity in the Thompson scheme

Solution

Please see attached file for details about the first updates. Update_PBL_Conv_p8c.pdf Please see attached file for details about the second updates Fupdate_Conv_p8c_TC.pptx