Aerosols in London Experiment on Radiative Transfer (ALERT)

据报告，由于城市气溶胶的存在，到达地球表面的太阳辐射量大幅度减少。在长波中，气溶胶的影响更不确定，然而，一些模拟和测量研究表明，城市气溶胶的存在可以起到增强下沉流到地面显着。更有趣的是，最近的工作表明，包含在表面的下行长波辐射光谱的信息可以用来诊断气溶胶对云微物理学的影响：一种间接的影响，预计将大大改变短波和长波云天空表面通量。在这里，我们建议通过ALERT首次同时测量短波和长波城市气溶胶辐射对城市环境的影响。通过一个独特的组合观测和建模工具，集中在伦敦中心，我们将研究两个主要假设：假设1：有一个可测量的城市晴空长波和短波直接辐射效应在表面由于气溶胶。假设二：由于云有效半径的可测量的变化，对城市短波和长波地面通量有间接的气溶胶辐射效应

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