Aerosol and cloud particles in tropical cirrus Anvil: Importance to radiation balance

With a multi-instrument approach, we determined the particle size spectrum between 20 nm and 1.6 mm diameter in the outflow portions of a convective tropical cloud. The measured particle size spectrum covered ≈ 12 orders of magnitude particle concentration over ≈ orders of magnitude particle size. Within this size interval, the particle spectrum revealed three modes: A cirrus haze nucleus mode, a cirrus haze particle mode, and a cirrus ice particle mode. In the optically active size range D > 0.4 μm, the particle population inside the cirrus cloud was enhanced above “background” concentrations by almost 4 orders of magnitude The prevalence of submicron particles led to the definition of cirrus haze nuclei which can grow along Köhler curves to radiatively important sizes. While cirrus ice particles carried most of the condensate mass, the cirrus haze particles dominated the surface area. Consequently, the presence of cirrus haze particles tripled extinction across the whole (visible and infrared) spectrum, and enhanced the IR single-scatter albedo of the cloud.