Dr. Shian-Jiann Lin

Physical Scientist, Chief of “Weather and Climate Dynamics Division”, NOAA/Geophysical Fluid Dynamics Laboratory

15:30, April 12, 2018

Room 101, Keyan Building, IAP

Abstract:

We are developing a new type of Unified Weather-Climate model with computationally efficient local cloud-resolving capability. This modeling system is based on an integrated dynamics-physics concept, in which several fast-acting physics (e.g., cloud microphysics and blocking by sub-grid orography) are directly incorporated into a new FV3 (nu-FV3, “new” Finite-Volume Dynamical Core on the Cubed-sphere) framework. This new modeling system improves the dynamics-physics interaction and increases the overall computational efficiency due to the separation of the fast-acting physics from the slow-physics, allowing a near tenfold increase in overall time step. We have built some of the SubGrid Orographically (SGO) forced processes into the new FV3 dynamics, which unavoidably breaks the traditional boundary between "dynamics" and "physics". We believe the boundary between the "dynamics" and "physics" set by the traditional modeling framework is one reason that limits modeling advancements in the past few decades. 

A preliminary version of this new type of GCRM is used for the DYAMOND project, an international comparison of global cloud resolving models.  We have carried out several 40-day "convective-parameterization-free" experiments across the gray-zone at three different horizontal resolutions: 13, 6.5, and 3.25 km. As a potential tool for sub-seasonal predictions, we shall analyze the forecast skill (first 10 days) as well as the systematic "climate basis" for the last 30 days.