Cloud fractionmediates the aerosol optical depth-cloud top height relationship

摘要

The observed strong link between aerosol optical depth (τ) and cloud top pressure (p_(top)) has frequently been interpreted as the invigoration of convective clouds by aerosol, with increased τ being strongly correlated with decreases in p_(top) (increases in cloud top height). A strong correlation between τ and cloud fraction (f_c) has also been observed. Using satellite-retrieved data, here we show that p_(top) is also strongly correlated to f_c, and when combined with the strong sensitivity between f_c and τ, a large proportion of the relationship between p_(top) and τ can be reconstructed. Given the uncertainties about the influence of aerosol-cloud interactions on the τ-f_c relationship, this suggests that a large fraction of the τ-p_(top) correlation may not be due to aerosol effects. Influences such as aerosol humidification and meteorology play an important role and should therefore be considered in studies of aerosol-cloud interactions.