最新科研进展
Dominant roles of subgrid-scale cloud structures in model diversity of cloud radiative effects
Authors：
Feng Zhang,1 Xin-Zhong Liang,2 Jiangnan Li,3 and Qingcun Zeng4
1 Earth System Science Interdisciplinary Center, University ofMaryland,College Park, Maryland, USA.
2 Earth System Science Interdisciplinary CenterDepartment of Atmospheric & Oceanic Science, University of Maryland, College Park,Maryland, USA.
3 Canadian Centre for Climate Modelling and Analysis, Environment Canada, Victoria, British Columbia, Canada.
4 International Center for Climate and Environment SciencesInstitute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China.
Abstract：
Aerosol-Radiation (CAR) ensemble modeling system was employed, offline driven by the ERA-Interim global data for July 2004 with no feedback considered. For evaluating each individual contribution from the existing scheme diversity of cloud horizontal inhomogeneity, cloud optical properties, cloud vertical overlap, and gas absorptions, several sets of numerical experiments were conducted. It is the first time to explicitly demonstrate that after removing most of the disagreement in cloud fields, model spreads of CREs among the CAR’s seven major radiation schemes, as well as those of radiative fluxes, dramatically diminish. Taking global mean CREs for example, their current model ranges can decrease to <4Wm-2 from about 10Wm-2 for shortwave and also to <4Wm-2 from 5–8Wm-2 for longwave. Dominant roles of subgrid-scale cloud structures (including vertical overlap and horizontal variability) were proven in general, explaining about 40–75% of the total model spreads. We have also found that model spreads of CREs are very sensitive to cloud cover fractions. Such nonlinear sensitivity can be largely reduced after removing the model difference in the treatments of cloud vertical overlap.
Keywords：
cloud subgrid-scale struction, model diversity, CAR
Citation:
Zhang, F., X.-Z. Liang, J. Li, and Q. Zeng (2013), Dominant roles of subgrid-scale cloud structures in model diversity of cloud radiative effects, J. Geophys. Res. Atmos., 118, 7733–7749, doi:10.1002/jgrd.50604.
