Comparison of Simulated Aerosols and Aerosol Effects in CAM5 Hindcasts and Climate Integrations

 

Authors

Catherine Chuang — Lawrence Livermore National Laboratory
Hsi-Yen Ma — Lawrence Livermore National Laboratory
Stephen Klein — Lawrence Livermore National Laboratory

Category

General Topics – Aerosol

Description

Aerosol plays a critical role in the Earth climate system by changing the planetary energy balance. The studies on estimates of aerosol effects are comprised of different approaches to identify radiative forcing from scattering and absorption of sunlight by aerosols as well as from aerosol-induced changes in clouds. In this work, two types of calculations, CAM5 hindcasts and climate integrations, are carried out to examine the similarities and differences in aerosol distributions and aerosol effects (direct and indirect) between short-term hindcasts and long-term simulations using the same physical model (i.e., CAM5/MAM3). Additional diagnostic calculations of radiation routine are performed to decompose the anthropogenic aerosol forcing. For hindcast runs in the Cloud-Associated Parameterizations Testbed (CAPT), we analyze the differences in clouds and radiative fluxes associated with aerosols under the similar large scale conditions close to observations. The magnitude of simulated aerosols effects is evaluated by differencing sets of CAM5 hindcasts in which the aerosol emissions are varied between those of pre-industrial and present day. For climate integrations in which the atmosphere can freely evolve, CAM5 is performed under different meteorology and aerosol emissions. Comparison of aerosol effects between short-term hindcasts and long-term simulations is scientifically interesting since one could separate aerosol effects from those that involve changes to atmospheric circulation and further explore the part of aerosol effects attributed to large scale circulation. More importantly, comparison of aerosol distributions between those two types of calculations will aid our future work using CAPT hindcasts to evaluate the simulated aerosol-cloud relationship with ARM data. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Lead PI

Catherine Chuang — Lawrence Livermore National Laboratory