Cloud fraction mediates the aerosol optical depth‐cloud top height relationship

Abstract

Abstract 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.