基于CMIP6强迫模拟分析人为气溶胶的气候效应(一) ——介绍NUIST模式评估结果
投稿时间:2018-09-19  修订日期:2019-01-14  点此下载全文
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作者单位E-mail
史湘军 南京信息工程大学 shixj@nuist.edu.cn 
沈沛洁 南京信息工程大学  
智协飞 南京信息工程大学  
朱寿鹏 南京信息工程大学  
吉璐莹 南京信息工程大学  
张海鹏 南京信息工程大学  
刘娇娇 南京信息工程大学  
基金项目:国家重点研发计划(2017YFA0604000);国家自然科学基金资助项目(41775095);南京信息工程大学人才启动经费(2243141601067)
中文摘要:为减少不同气候模式评估气溶胶气候效应的差异,第六次耦合模式比较计划(Coupled Model Intercomparison Project Phase 6,CMIP6)直接给定了人为气溶胶强迫数据。因此,有必要基于此强迫数据重新评估气溶胶气候效应。本研究首先将CMIP6给出的描述人为气溶胶强迫的模块引入南京信息工程大学(Nanjing University of Information Science and Technology,NUIST)的地球系统模式(The NUIST Earth System Model,NESM)。之后,利用NESM模式评估地球辐射收支平衡对此人为气溶胶强迫的响应,并分析模式模拟结果的不确定性。评估给出的人为气溶胶有效辐射强迫为?0.45(±0.28)W?m?2。其中,气溶胶直接辐射效应为?0.34(±0.01)W?m?2,与第二次气溶胶比较计划(The second phase of Aerosol Comparisons between Observations and Models,AeroCom II)的评估结果基本一致;气溶胶对云辐射强迫的影响(包括半直接效应和间接效应)为?0.10(±0.30)W?m?2,明显受到模式内部变率的干扰,具有较大的不确定性。
中文关键词:CMIP6  NESM  人为气溶胶  有效辐射强迫  不确定性
 
A Modeling Study on Anthropogenic Aerosol Effects Based on CMIP6 Forcing. Part I: NUIST model results and corresponding Estimation
Abstract:The ultimate purpose of this study is to estimate anthropogenic aerosol effects on the planetary energy balance based on a hypothetical anthropogenic aerosol forcings given by Coupled Model Intercomparison Project Phase 6 (CMIP6). In order to get the confidence of these estimates, we also analyze how natural variability contributes to uncertainty in these estimates. The climate model used in this study is NESM, which is an earth system model developed by Nanjing University of Information Science and Technology (NUIST). The anthropogenic aerosol forcing officially recommended by CMIP6 is a hypothetical dataset derived from the second version of the Max Planck Institute Aerosol Climatology (MACv2-SP). MACv2-SP is implemented into NESM model to represent anthropogenic aerosol optical properties and an associated Twomey effect. NESM model results show that the global annual mean anthropogenic aerosol optical depth (AOD) in the visible band and the normalized change in cloud droplet number (dNovrN) calculated from MACv2-SP are 0.025, and 1.075, respectively. These anthropogenic aerosol forcings used in this study are similar to those in the paper, which introduce MACv2-SP. This indicates the MACv2-SP is used correctly in NESM model. In this study, the fixed-SST method is used to diagnose aerosol effective radiative forcing (ERF). We set up two experiments: Base and Both. The Base experiment turns MACv2-SP off. The anthropogenic aerosol optical properties and Twomey effect described by MACv2-SP are used in the Both experiment. The Base and Both experiments results show that anthropogenic aerosol ERF is estimated at ?0.45 W?m?2. The contribution to this ERF from direct radiative effect is ?0.34 W?m?2, which is significantly larger than its corresponding standard deviation (0.01 W?m?2). The contribution to this ERF from aerosol-induced changes in clouds (i.e., semi-direct effect and Twomey effect) is ?0.10 W?m?2, which is only one third of its corresponding standard deviation (0.30 W?m?2). These indicate that climate model could give high confidence in estimating direct radiative effect, whereas very low confidence in estimating aerosol effects on cloud radiative forcing. Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5) assess ERF using expert judgment to be –0.9 W?m?2 with a 5 to 95% uncertainty range of –1.9 to –0.1 W?m?2 (medium confidence). Compared with IPCC AR5, the ERF from this study is in the uncertainty range although it is weak (less negative). The second phase of Aerosol Comparisons between Observations and Models (AeroCom II) model results give direct radiative effect estimate of –0.35 W?m?2, with a model range of about –0.60 to –0.13 W?m?2. The direct radiative effect estimate from our model results is similar to AeroCom II. This also suggests that the aerosol effects on cloud radiative forcing are the main sources of the difference in ERF between this study and IPCC AR5. CMIP6 only considers Twomey effect; other aerosol indirect effects are not included. This might be the reason why aerosol effects on cloud radiative forcing this study is weaker than IPCC AR5.
keywords:CMIP6  NESM  Anthropogenic Aerosol  Effective Radiative Forcing  Cloud Radiative Forcing  Uncertainty
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