Application and evaluation of a new radiation code under McICA scheme in BCC_AGCM2.0.1

Abstract

Abstract. This research incorporates the correlated k distribution BCC-RAD radiation model into the climate model BCC_AGCM2.0.1 and examines the change in climate simulation by implementation of the new radiation algorithm. It is shown that both clear-sky radiation fluxes and cloud radiative forcings (CRFs) are improved. The modeled atmospheric temperature and specific humidity are also improved due to changes in radiative heating rates, which most likely stem from the revised treatment of gaseous absorption.Subgrid cloud variability, including vertical overlap of fractional clouds and horizontal inhomogeneity in cloud condensate, is addressed by using the Monte Carlo Independent Column Approximation (McICA) method. In McICA, a cloud-type-dependent function for cloud fraction decorrelation length, which gives zonal mean results very close to the observations of CloudSat/CALIPSO, is developed. Compared to utilizing a globally constant decorrelation length, the maximum changes in seasonal CRFs by the new scheme can be as large as 10 and 20 W m −2 for longwave (LW) and shortwave (SW) CRFs, respectively, mostly located in the tropics. The inclusion of an observation-based horizontal inhomogeneity of cloud condensate has also a significant impact on CRFs, with global means of ∼ 1.5 W m −2 and ∼ 3.7 Wm −2 for LW and SW CRFs at the top of atmosphere (TOA), respectively. Generally, incorporating McICA and horizontal inhomogeneity of cloud condensate in the BCC-RAD model reduces global mean TOA and surface SW and LW flux biases in BCC_AGCM2.0.1.These results demonstrate the feasibility of the new model configuration to be used in BCC_AGCM2.0.1 for climate simulations, and also indicate that more detailed real-world information on cloud structures should be obtained to constrain cloud settings in McICA in the future.

Projected response of East Asian summer monsoon system to future reductions in emissions of anthropogenic aerosols and their precursors

“…The EAMR is designated as the region 0-50°N, 100°E-140°E. Zhang et al (2012Zhang et al ( , 2014, and Wang et al (2014). The performance of the model has been evaluated by Wang et al (2014), Zhang et al (2014), and Wang et al (2015) in detail.…”

Variation in entrainment rate and relationship with cloud microphysical properties on the scale of 5 m

“…Clouds play important roles in global radiation budget and climate change [1][2][3][4][5][6][7]. Cumulus parameterization in climate models affects the simulations of precipitation, intraseasonal oscillation, and climate [8][9][10][11][12].…”

Simultaneous reductions in emissions of black carbon and co-emitted species will weaken the aerosol net cooling effect

“…We use the aerosol-climate atmosphere-only model BCC_AGCM2.0.1_CUACE/Aero developed by Zhang et al (2012a), and improved by Jing and Zhang (2013), Zhang et al (2014), and Z. L. in this study. The aerosol direct, semi-direct, and indirect effects (albedo and lifetime indirect effects on stratiform clouds) have been included in BCC_AGCM2.0.1_CUACE/Aero.…”