Estimating the CMIP6 Anthropogenic Aerosol Radiative Effects with the Advantage of Prescribed Aerosol Forcing

Xiangjun Shi,Wentao Zhang,Chunhan Li,Lijuan Li,Jiaojiao Liu

doi:10.3390/atmos12030406

Abstract

The prescribed anthropogenic aerosol forcing recommended by Coupled Model Intercomparison Project Phase 6 (CMIP6) was implemented in an atmospheric model. With the reduced complexity of anthropogenic aerosol forcing, each component of anthropogenic aerosol effective radiative forcing (ERF) can be estimated by one or more calculation methods, especially for instantaneous radiative forcing (RF) from aerosol–radiation interactions (RFari) and aerosol–cloud interactions (RFaci). Simulation results show that the choice of calculation method might impact the magnitude and reliability of RFari. The RFaci—calculated by double radiation calls—is the definition-based Twomey effect, which previously was impossible to diagnose using the default model with physically based aerosol–cloud interactions. The RFari and RFaci determined from present-day simulations are very robust and can be used as offline simulation results. The robust RFari, RFaci, and corresponding radiative forcing efficiencies (i.e., the impact of environmental properties) are very useful for analyzing anthropogenic aerosol radiative effects. For instance, from 1975 to 2000, both RFari and RFaci showed a clear response to the spatial change of anthropogenic aerosol. The global average RF (RFari + RFaci) has enhanced (more negative) by ~6%, even with a slight decrease in the global average anthropogenic aerosol, and this can be explained by the spatial pattern of radiative forcing efficiency.

Highlights

One of the guiding questions of the Coupled Model Intercomparison Project Phase 6(CMIP6) is “how does the earth system respond to forcing?” [1]
The comparison between AaFCc RAD−BASE (AaFRAD−BASE ) and aFACc RAD indicates that the RF from anthropogenic aerosol–radiation interactions (RFari) estimated by a model diagnostic radiative forcing variable from one simulation is more robust than that estimated by the difference between two simulations
The prescribed anthropogenic aerosol forcing recommended by CMIP6 was implemented in the Grid-point Atmospheric Model of IAP LASG (GAMIL) model

Summary

Introduction

One of the guiding questions of the Coupled Model Intercomparison Project Phase 6(CMIP6) is “how does the earth system respond to forcing?” [1]. Idealized experiments have been designed to highlight and understand the differences in climate model responses to specified common anthropogenic aerosol forcing [4,5]. Given these concepts, a simple plume implementation of the second version of the Max Planck. Anthropogenic aerosol (“a”) direct radiative forcing is named as aFXX. Background cloud (“C”, without the Twomey effect) forcing is named as CFXX. The instantaneous Twomey effect (“c”) is named cFxx. Here, the subscript “XX” refers to background radiative forcing factors

Methods

Results

Conclusion