Understanding the influence of water uptake on absorption by aerosols

Abstract:

Absorption by atmospheric aerosols has large impacts on the global radiation budget. Mixing of absorbing (e.g., black carbon) and non-absorbing aerosol components can enhance absorption. While this has been established for many aerosol components, clear understanding of the specific influence of the arguably most ubiquitous and dynamic aerosol component—liquid water—remains elusive. Commonly used models indicate a large influence of aerosol liquid water on light absorption. Yet, there are few observations, either lab or field, that provide foundational support for these model results. Here, we discuss results of absorption measurements made at dry and elevated relative humidities (>80%) using newly developed instrumentation, focusing on the response of a variety of different absorbing and non-absorbing aerosol types, and their mixtures, to water uptake. Effects of mixing of non- or weakly hygroscopic absorbing materials with highly hygroscopic non-absorbing materials will be explicitly considered, and used to develop fuller understanding of how aerosol liquid water affects light absorption.