Title: Aerosol specification in single-column Community Atmosphere Model version 5

Abstract

Single-column model (SCM) capability is an important tool for general circulation model development. In this study, the SCM mode of version 5 of the Community Atmosphere Model (CAM5) is shown to handle aerosol initialization and advection improperly, resulting in aerosol, cloud-droplet, and ice crystal concentrations which are typically much lower than observed or simulated by CAM5 in global mode. This deficiency has a major impact on stratiform cloud simulations but has little impact on convective case studies because aerosol is currently not used by CAM5 convective schemes and convective cases are typically longer in duration (so initialization is less important). By imposing fixed aerosol or cloud-droplet and crystal number concentrations, the aerosol issues described above can be avoided. Sensitivity studies using these idealizations suggest that the Meyers et al. (1992) ice nucleation scheme prevents mixed-phase cloud from existing by producing too many ice crystals. Microphysics is shown to strongly deplete cloud water in stratiform cases, indicating problems with sequential splitting in CAM5 and the need for careful interpretation of output from sequentially split climate models. Droplet concentration in the general circulation model (GCM) version of CAM5 is also shown to be far too low (~ 25 cm⁻³) at the southernmore » Great Plains (SGP) Atmospheric Radiation Measurement (ARM) site.« less

Authors:

Lebassi-Habtezion, B.; Caldwell, P. M.

Publication Date:

Fri Mar 27 00:00:00 EDT 2015

Research Org.:

Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR). Scientific Discovery through Advanced Computing (SciDAC)

OSTI Identifier:

1197696

Alternate Identifier(s):

OSTI ID: 1879273

Report Number(s):

LLNL-JRNL-662549
Journal ID: ISSN 1991-9603

Grant/Contract Number:  

AC52-07NA27344

Resource Type:

Published Article

Journal Name:

Geoscientific Model Development (Online)

Additional Journal Information:

Journal Name: Geoscientific Model Development (Online) Journal Volume: 8 Journal Issue: 3; Journal ID: ISSN 1991-9603

Publisher:

Copernicus Publications, EGU

Country of Publication:

Germany

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES