Authors: Noah Tewksbury, Edward Strobach, Bin Liu, JiLi Dong
The National Centers for Environmental Prediction (NCEP) is transitioning it’s modeling suite to the Finite-Volume Cubed Sphere (FV3) dynamical core, which will help reach the future goal of a unified operational production suite. This transition to a unified operational production suite has allowed the NCEP Environmental Modeling Center (EMC) to develop a 3-km horizontal resolution model with convection-allowing capabilities. Due to these recent upgrades that were implemented in June 2019, a performance evaluation of the FV3 Stand-Alone Regional (SAR) is required.
Comparisons of six different FV3-SAR model runs that include two different microphysics schemes and three planetary boundary layer (PBL) schemes are examined with the recent upgrade to the FV3GFS. All model runs examined in this study were initialized on 10/09/2018 06UTC to investigate the intensification of Hurricane Michael as it made landfall. The two microphysics schemes that were used for this case are the GFDL and Thompson schemes. The PBL schemes include the operational PBL (HYB-EDMF), which is an Eddy Diffusivity Mass Flux Scheme that uses Prandtl number relations and stability functions dependent upon PBL regime to calculate eddy diffusivities, while the other two are separate versions of the scale aware TKE-EDMF (sa-TKE-EDMF) that use an asymptotic mixing length and TKE to calculate eddy diffusivities. The newer version of sa-TKE-EDMF includes an improvement to inversions to alleviate the recent cold bias issue.
Preliminary results show that the Thompson microphysics scheme is more sensitive to the choice of PBL compared to the GFDL microphysics scheme, which furthermore was shown to improve the intensification of Hurricane Michael. A detailed analysis of the 3D structure for Hurricane Michael is included to examine the contributing factors that led to enhanced intensification when pairing Thompson with sa-TKE-EDMF over the HYB-EDMF PBL scheme. Comparisons with the maximum reflectivity field from observed radar are also analyzed with the model simulated reflectivity prior to landfall to get a sense of structural differences as well as similarities between schemes. This will also be followed up with how the same model, microphysics, and PBL schemes handled another storm, Hurricane Florence, but with more of a focus on mean sea level pressure and maximum wind speed.
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