由于云的时空尺度非常宽广,云微物理参数化方案一直是气候模式中的薄弱环节.本文借鉴中尺度模式云微物理方案从双参数向三参数扩展的思路方法,发展了联合地球系统模式(Community Integrated Earth System Model,CIESM)三参数冰相云微物...由于云的时空尺度非常宽广,云微物理参数化方案一直是气候模式中的薄弱环节.本文借鉴中尺度模式云微物理方案从双参数向三参数扩展的思路方法,发展了联合地球系统模式(Community Integrated Earth System Model,CIESM)三参数冰相云微物理方案,弥补了默认双参数方案不能预报冰晶粒径分布谱形参数(μ)的不足,进而分析了双、三参数方案对气候模拟的影响.模拟结果表明,相较于双参数方案(μ为0),三参数方案预报得出的μ更为合理,其在垂直分布上整体呈现出“高层小低层大”的特点,高层的低值主要是由于冰晶核化以及较大的冰晶粒子沉降后粒子之间相互混合导致的,而低层的高值主要是由于冰晶粒子在沉降过程中的粒子分选机制导致的.与双、三参数方案中μ的差异相呼应,模式模拟的气候平均态出现明显差异,其中三参数方案模拟的总云云量、低云云量、中云云量和总降水相较于双参数方案更接近观测结果,高云云量的误差增大.其中总降水的改进主要是由于高云云量的增加,大气稳定度增加,对流性降水减少.此外,还调整了相关参数,以改善模式对辐射的模拟能力.总之,本文在全球气候模式中评估了双、三参数方案对于模拟气候平均态的不同影响,为气候模式中云微物理方案的发展改进提供了一定的参考意义.展开更多
Quantifying the radiative forcing due to aerosol-cloud interactions especially through cirrus clouds remains chal- lenging because of our limited understanding of aerosol and cloud processes. In this study, we investi...Quantifying the radiative forcing due to aerosol-cloud interactions especially through cirrus clouds remains chal- lenging because of our limited understanding of aerosol and cloud processes. In this study, we investigate the anthro-pogenic aerosol indirect forcing （AIF） through cirrus clouds using the Community Atmosphere Model version 5 （CAM5） with a state-of-the-art treatment of ice nucleation. We adopt a new approach to isolate anthropogenic AIF through cirrus clouds in which ice nucleation parameterization is driven by prescribed pre-industrial （PI） and present- day （PD） aerosols, respectively. Sensitivities of anthropogenic ice AIF （i.e., anthropogenic AIF through cirrus clouds） to different ice nucleation parameterizations, homogeneous freezing occurrence, and uncertainties in the cloud micro- physics scheme are investigated. Results of sensitivity experiments show that the change （PD minus PI） in global an-nual mean longwave cloud forcing （i.e., longwave anthropogenic ice AIF） ranges from 0.14 to 0.35 W m^-2, the change in global annual mean shortwave cloud forcing （i.e., shortwave anthropogenic ice AIF） from -0.47 to -0.20 W m^-2, and the change in net cloud forcing from -0.12 to 0.05 W m^-2. Our results suggest that different ice nucle-ation parameterizations are an important factor for the large uncertainty of anthropogenic ice AIF. Furthermore, im-proved understanding of the spatial and temporal occurrence characteristics of homogeneous freezing events and the mean states of cirrus cloud properties are also important for constraining anthropogenic ice AIF.展开更多
文摘由于云的时空尺度非常宽广,云微物理参数化方案一直是气候模式中的薄弱环节.本文借鉴中尺度模式云微物理方案从双参数向三参数扩展的思路方法,发展了联合地球系统模式(Community Integrated Earth System Model,CIESM)三参数冰相云微物理方案,弥补了默认双参数方案不能预报冰晶粒径分布谱形参数(μ)的不足,进而分析了双、三参数方案对气候模拟的影响.模拟结果表明,相较于双参数方案(μ为0),三参数方案预报得出的μ更为合理,其在垂直分布上整体呈现出“高层小低层大”的特点,高层的低值主要是由于冰晶核化以及较大的冰晶粒子沉降后粒子之间相互混合导致的,而低层的高值主要是由于冰晶粒子在沉降过程中的粒子分选机制导致的.与双、三参数方案中μ的差异相呼应,模式模拟的气候平均态出现明显差异,其中三参数方案模拟的总云云量、低云云量、中云云量和总降水相较于双参数方案更接近观测结果,高云云量的误差增大.其中总降水的改进主要是由于高云云量的增加,大气稳定度增加,对流性降水减少.此外,还调整了相关参数,以改善模式对辐射的模拟能力.总之,本文在全球气候模式中评估了双、三参数方案对于模拟气候平均态的不同影响,为气候模式中云微物理方案的发展改进提供了一定的参考意义.
基金Supported by the National Science Foundation of US(ATM-1642289)National Natural Science Foundation of China(41775095)
文摘Quantifying the radiative forcing due to aerosol-cloud interactions especially through cirrus clouds remains chal- lenging because of our limited understanding of aerosol and cloud processes. In this study, we investigate the anthro-pogenic aerosol indirect forcing （AIF） through cirrus clouds using the Community Atmosphere Model version 5 （CAM5） with a state-of-the-art treatment of ice nucleation. We adopt a new approach to isolate anthropogenic AIF through cirrus clouds in which ice nucleation parameterization is driven by prescribed pre-industrial （PI） and present- day （PD） aerosols, respectively. Sensitivities of anthropogenic ice AIF （i.e., anthropogenic AIF through cirrus clouds） to different ice nucleation parameterizations, homogeneous freezing occurrence, and uncertainties in the cloud micro- physics scheme are investigated. Results of sensitivity experiments show that the change （PD minus PI） in global an-nual mean longwave cloud forcing （i.e., longwave anthropogenic ice AIF） ranges from 0.14 to 0.35 W m^-2, the change in global annual mean shortwave cloud forcing （i.e., shortwave anthropogenic ice AIF） from -0.47 to -0.20 W m^-2, and the change in net cloud forcing from -0.12 to 0.05 W m^-2. Our results suggest that different ice nucle-ation parameterizations are an important factor for the large uncertainty of anthropogenic ice AIF. Furthermore, im-proved understanding of the spatial and temporal occurrence characteristics of homogeneous freezing events and the mean states of cirrus cloud properties are also important for constraining anthropogenic ice AIF.
