Water uptake¶
Hygroscopicity refers to the ability of a material to acquire water from the ambient air; the physical process by which aerosol particles obtain water is referred to as hygroscopic growth. The change of water content in a particle modifies its size, morphology, chemical composition and optical properties, thus impacting other physical processes including coagulation, condensation, deposition and the interaction with radiation. From a numerical modeling perspective, it is useful to consider two types of hygroscopic growth: (i) if the aerosol water content changes and the particle remains an interstitial particle, the water absorption/desorption process is referred to as water uptake; MAM's representation of water uptake is described in this document. (ii) in a very moist environment, a particle can grow substantially and become a cloud droplet. This latter scenario is known as aerosol activation or cloud nucleation, and is described in a separate document.