Abstract

Abstract. Radiative kernels at the top of the atmosphere are useful for decomposing changes in atmospheric radiative fluxes due to feedbacks from atmosphere and surface temperature, water vapor, and surface albedo. Here we describe and validate radiative kernels calculated with the large-ensemble version of CAM5, CESM1.1.2, at the top of the atmosphere and the surface. Estimates of the radiative forcing from greenhouse gases and aerosols in RCP8.5 in the CESM large-ensemble simulations are also diagnosed. As an application, feedbacks are calculated for the CESM large ensemble. The kernels are freely available at https://doi.org/10.5065/D6F47MT6, and accompanying software can be downloaded from https://github.com/apendergrass/cam5-kernels.

Highlights

  • A radiative feedback kernel is the radiative response to a small perturbation in, for example, temperature or water vapor

  • The only publicly available model-based surface radiative kernels are from ECHAM5 (Previdi, 2010) and MPIESM-LR, which is a more recent version of the ECHAM model

  • In order to calculate the radiative feedback kernels, we make offline radiative transfer calculations following the methodology of Soden and Held (2006) with the Parallel Offline Radiative Transfer (PORT; Conley et al, 2013) code, updated for compatibility with CAM5 microphysics and RRTMG radiation (Iacono et al, 2008)

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Summary

Introduction

A radiative feedback kernel is the radiative response to a small perturbation in, for example, temperature or water vapor. Used TOA radiative kernels were calculated with the GFDL model (Soden and Held, 2006) Other kernels include those from CAM3 (Shell et al, 2008) and more recently from the MPI-ESM-LR model (Block and Mauritsen, 2013). We describe and validate radiative kernels calculated with CESM-CAM5 (Hurrell et al, 2013) for the top of the atmosphere and the surface. These radiative feedback kernels were calculated with CESM version 1.1.2, the same as that used for the 40-member CESM large ensemble (Kay et al, 2015). We include estimates of radiative forcing due to greenhouse gases and aerosols in RCP8.5 in the CESM large-ensemble simulations, which are necessary for calculating the cloud feedback using radiative kernels

Calculations
Radiative kernels
Atmospheric temperature kernel
Surface temperature kernel
Atmospheric moisture kernel
Surface albedo kernel
Forcing
Greenhouse gas forcing
Aerosol forcing
Validation
Application
Code and data availability
Path forward
Full Text
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