Black carbon solar absorption suppresses turbulence in the atmospheric boundary layer
Black carbon solar absorption suppresses turbulence in the atmospheric boundary layer
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DOI：
10.1073/pnas.1525746113
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发表时间：
2016-10
期刊：
影响因子：
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通讯作者：
E. Wilcox;Rick M. Thomas;P. S. Praveen;K. Pistone;F. Bender;V. Ramanathan
中科院分区：
文献类型：
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作者：
E. Wilcox;Rick M. Thomas;P. S. Praveen;K. Pistone;F. Bender;V. Ramanathan
气溶胶对气候的冷却作用和气溶胶对云的改变一直受到广泛的争论，因为量化它们的影响对限制当前的气候变化很重要。在这里，我们提出的测量湍流从无人驾驶航空器。我们发现，黑碳（BC）气溶胶对阳光的吸收抑制了低层大气中的湍流，对人类化石燃料和生物质燃烧产生的BC排放对环境的影响产生了重要影响。提出了一种机制，链接到更高的云抑制湍流。这些结果突出了理解和观察湍流在研究气溶胶对云的影响中的作用的重要性。抑制湍流也加剧了能见度和污染对人类健康的影响。吸收太阳光的气溶胶引入云凝结核和辐射加热可以改变低云的厚度和覆盖范围，产生显著的气候辐射强迫。云覆盖率和深度的变化，以响应不断变化的气溶胶的大小和迹象的影响，由多云的大气湍流动力学，但气溶胶太阳能吸收和湍流通量的综合测量迄今尚未报告。在这里，我们报告这样的综合测量从无人机（UAV）在CARDEX（云气溶胶辐射强迫和动力学实验）调查进行了北方印度洋。无人机和地面数据显示，大气底部的表面混合层中湍流动能减少，同时吸收的黑碳气溶胶增加。由于气溶胶辐射加热和湍流减少，污染条件与较暖和较浅的表面混合层相吻合。污染的地面混合层也观察到更潮湿的相对湿度较高。更大的湿度会促进云的发展，污染云穿透到表面混合层顶部以上的更高位置就是证明。由于湍流较弱，从覆盖表面混合层的逆温上方进入表面层的干燥空气夹带减少，可能有助于在污染条件下表面层中的相对湿度较高。湍流的测量对于研究气溶胶对云的影响是很重要的。此外，减少湍流会加剧高浓度细颗粒物对人类健康的影响，以及有利于低能见度雾事件的条件。
Significance The cooling effect of aerosols on climate and the modification of clouds by aerosols have been widely debated, because quantifying their effects is important for constraining current climate change. Here we present measurements of turbulence from unmanned aerial vehicles. We find that absorption of sunlight by black carbon (BC) aerosols suppresses turbulence in the lower atmosphere, with important consequences for the environmental impacts of BC emissions from anthropogenic fossil fuel and biomass burning. A mechanism is proposed that links the suppressed turbulence to taller clouds. These results highlight the importance of understanding and observing the role of turbulence in studies of aerosol impacts on clouds. Suppressed turbulence also exacerbates the visibility and human health impacts of pollution. The introduction of cloud condensation nuclei and radiative heating by sunlight-absorbing aerosols can modify the thickness and coverage of low clouds, yielding significant radiative forcing of climate. The magnitude and sign of changes in cloud coverage and depth in response to changing aerosols are impacted by turbulent dynamics of the cloudy atmosphere, but integrated measurements of aerosol solar absorption and turbulent fluxes have not been reported thus far. Here we report such integrated measurements made from unmanned aerial vehicles (UAVs) during the CARDEX (Cloud Aerosol Radiative Forcing and Dynamics Experiment) investigation conducted over the northern Indian Ocean. The UAV and surface data reveal a reduction in turbulent kinetic energy in the surface mixed layer at the base of the atmosphere concurrent with an increase in absorbing black carbon aerosols. Polluted conditions coincide with a warmer and shallower surface mixed layer because of aerosol radiative heating and reduced turbulence. The polluted surface mixed layer was also observed to be more humid with higher relative humidity. Greater humidity enhances cloud development, as evidenced by polluted clouds that penetrate higher above the top of the surface mixed layer. Reduced entrainment of dry air into the surface layer from above the inversion capping the surface mixed layer, due to weaker turbulence, may contribute to higher relative humidity in the surface layer during polluted conditions. Measurements of turbulence are important for studies of aerosol effects on clouds. Moreover, reduced turbulence can exacerbate both the human health impacts of high concentrations of fine particles and conditions favorable for low-visibility fog events.