Observations of the shelf environment rarely associate internal solitary waves (ISWs) with the impact of their passage. An experiment observed during the Coastal Mixing and Optics 1996( CMO ’96), a sequence of long internal waves on a coastal shelf is reported, including both mode-1 and mode-2 waves, together with evidence related to the interaction of propagating ISWs and the benthic boundary layer. The observed ISW dynamics is shown to present a repetitive pattern or ‘climate cycle’. The ISW-associated benthic signature described here occurs frequently (at least once a day) in the CMO ’96coastal area and suggests that ISWs under calm, summer-like conditions may have a decisive influence on the fate of near-bottom pollutants or biological processes in shelf regions.
The physical and optical properties of an atmospheric aerosol mixture depend on a number of factors. The relative humidity influences the size of hydroscopic particles and the effective radius of an aerosol mixture. In consequence, values of the aerosol extinction, the aerosol optical thickness and the Ångström coefficient are modified. A similar effect is observed when the aerosol composition changes. A higher content of small aerosol particles causes the effective radius of an aerosol mixture to decrease and the Ångström coefficient to increase. Both effects are analysed in this paper. The parameters of the size distribution and the type of components used to represent natural atmospheric aerosol mixtures are based on experimental data. The main components are sea-salts (SSA), anthropogenic salts (WS, e.g. NH4HSO4, NH4NO3, (NH4)2SO4), organic carbon (OC) and black carbon (BC). The aerosol optical thickness is modelled using the external mixing approach. The influence of relative humidity on the optical and physical properties of the following aerosol mixtures is investigated: (SSA&WS), (SSA&OC), (SSA&BC), (SSA, WS&OC) and (WS, OC&BC). It is demonstrated that the Ångström coefficient can be used as a rough indicator of the aerosol type.