Ambient humidity has a significant effect on the scattering effects of hygroscopic particles.
Typically, the higher the humidity, the greater the scattering effect. Radiative forcing data needs to be compared at the ambient humidity levels, however in order to compare the scattering effect of aerosols globally, GAW recommends that the relative humidity is less than 40%.
Climate change modelling relies upon the aerosol asymmetry parameter, but most assume it to be 0.7. Aerosol source, seasonal variation and changes in relative humidity influence the number, size and shape of aerosols and therefore affect the aerosol asymmetry parameter (Ogren, 2006). For instance a change of RH between 40% to 85% will influence this parameter by up to 20%.
Combining both the polar nephelometer and the ability to compare ambient humidity with a stepping gradient is a powerful new tool to gain further of the aerosol coating and its properties.
new Ecotech sample conditioning system can also be used with any other
aerosol monitoring instrument to examine the effects of humidity.