Aerosol Specification in Single-Column CAM5

Wednesday, 17 December 2014
Bereket L Habtezion and Peter Caldwell, Lawrence Livermore National Laboratory, Livermore, CA, United States
The importance of aerosol specification in climate models for direct and indirect effects in climate had been widely documented in many research studies. The inclusion of the prognostic aerosol model in the Community Atmospheric Model (CAM) is a major breakthrough in the model development of CAM. The Single Column Model (SCM) version of CAM is very useful tool for an efficient development of model numeric and physics. However, SCM hasn’t been well maintained due to focus to the full 3D model. SCM hasn’t been updated appropriately to handle the prognostic aerosol model in CAM. In this study we identify the problems of using the default SCM version of CAM5 (SCAM5) and introduce fixes to the identified problems. We used four different aerosol specification methods in the SCM simulations. The aerosol specifications are default model (with prognostic aerosol, initialized to zero), prescribed aerosol (with monthly climatological aerosol values), observed aerosol (with aerosols from observations), and a case with fixed droplet concentration. We use SCM simulations with the different aerosol specification for a variety of cloud regimes. The sites used for these study include subtropical drizzling stratocumulus (DYCOMSRF02), multi-level Arctic clouds (MPACE-B), shallow convection (RICO), and summertime mid-latitude continental convection (ARM95). Simulations at the default time step and default model resolution were conducted and results are analyzed and compared to observations and previous Large Eddy Simulation (LES) studies.