Uncertainties in aerosol direct and indirect effects attributed to uncertainties in convective transport parameterizations
Uncertainties in aerosol direct and indirect effects attributed to uncertainties in convective transport parameterizations
复制标题
对流传输参数化的不确定性导致气溶胶直接和间接影响的不确定性
DOI：
10.1016/j.atmosres.2012.06.022
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发表时间：
2012
影响因子：
5.5
通讯作者：
T. Storelvmo
中科院分区：
文献类型：
--
作者：
T. Storelvmo
深层对流是气溶胶颗粒的重要输送机制，使气溶胶颗粒能够被提升到可以从源区远距离输送到偏远地区的水平。区域气溶胶效应对深层湿对流夹带速率的敏感性已在全球模型框架中进行了探索，并发现这对于大气表面和顶部的辐射平衡至关重要。事实上，深对流频繁的区域通常与黑碳排放特别高的区域重合，这一事实被发现是理解这种夹带敏感性的一个重要因素。更多的夹带导致对流羽流变浅，并且从边界层到源区对流层上层的气溶胶传输减少。结果，源区边界层气溶胶浓度增加，而全球对流层上层气溶胶浓度减少。这通常会导致污染地区气溶胶效应较强，而偏远地区气溶胶效应较弱。由于黑碳颗粒具有吸收太阳辐射的能力，因此降低其浓度会导致更多的太阳辐射反射回太空，尤其是在明亮的表面上。相反，在地表，更多的夹带意味着除源区以外的所有地方都有更多的下涌短波辐射。由于夹带增加而导致边界层气溶胶浓度增加的区域观察到更强的气溶胶间接效应，而其他地方的情况则相反。这项研究强调，清洁地区与污染地区的气溶胶直接和间接影响的相对强度主要取决于深对流云的夹带率，这一过程目前尚未得到很好的理解和量化。
Deep convection is an important transport mechanism for aerosol particles, allowing them to be lifted to levels where they are subject to long-range transport from source regions to remote regions. The sensitivity of regional aerosol effects to the rate of entrainment in deep moist convection has been explored in a global modeling framework, and found to be crucial for the radiative balance both at the surface and at the top of the atmosphere. The fact that regions where deep convection is frequent often coincide with regions of particularly high black carbon emissions is found to be an important factor in understanding this sensitivity to entrainment. More entrainment leads to shallower convective plumes and less aerosol transport from the boundary layer to the upper troposphere in source regions. As a result, boundary layer aerosol concentrations are increased in source regions, while upper tropospheric aerosol concentrations are reduced globally. This generally leads to stronger aerosol effects in polluted regions and weaker aerosol effects in remote regions. Because black carbon particles have the ability to absorb solar radiation, reducing their concentration leads to more solar radiation reflected back to space, especially over bright surfaces. Conversely, at the surface more entrainment means more downwelling shortwave radiation everywhere but in source regions. Regions that experience increased aerosol concentrations in the boundary layer in response to increased entrainment observed a stronger aerosol indirect effect, while the opposite was true everywhere else. This study highlights that the relative strengths of the aerosol direct and indirect effects in clean versus polluted regions depend crucially on the rate of entrainment in deep convective clouds, a process that is presently not well understood and quantified.