Aerosols in London Experiment on Radiative Transfer (ALERT)

据报道，在全球许多地区，由于城市气溶胶的存在，到达地球表面的太阳辐射量大幅减少。在长波中，气溶胶的影响更加不确定，然而，一些模拟和测量研究表明，城市气溶胶的存在可以显著增强地表的下行通量。更有趣的是，最近的工作表明，地表下潜长波辐射光谱中包含的信息可用于诊断气溶胶对云微物理的影响：这种间接影响预计将大大改变云天表面短波和长波通量。在此，我们首次提出通过ALERT同时测量短波和长波城市气溶胶对城市环境的辐射效应。通过观测和建模工具的独特组合，以伦敦市中心为重点，我们将检验两个主要假设：假设1：由于气溶胶，在城市晴空表面存在可测量的长波和短波直接辐射效应。假设2：由于云有效半径可测量的变化，存在气溶胶对城市短波和长波表面通量的间接辐射效应

A substantial reduction in the amount of solar radiation reaching the Earth's surface, due to the presence of urban aerosol, has been reported for a variety of global locations. In the long-wave, the aerosol impact is more uncertain, however, a number of modeling and measurement studies suggest that the presence of urban aerosol can act to enhance downwelling fluxes to the surface significantly. Even more intriguingly, recent work has indicated that information contained in the spectrum of downwelling long-wave radiation at the surface can be employed to diagnose an aerosol effect on cloud microphysics: an indirect impact which would be expected to substantially modify both short-wave and long-wave cloudy-sky surface fluxes. Here, through ALERT, we propose to simultaneously measure, for the first time, the short-wave and long-wave urban aerosol radiative effect on the urban environment. Through a unique combination of observational and modeling tools, focused on central London, we will examine two principal hypotheses: Hypothesis 1: There is a measurable urban clear-sky long-wave and short-wave direct radiative effect at the surface due to aerosols. Hypothesis 2: There is an indirect aerosol radiative effect on urban short-wave and long-wave surface fluxes due to measurable shifts in cloud effective radius