Shallow Convective Cloud Field Lifetime as a Key Factor for Evaluating Aerosol Effects

Clouds control much of the Earth's energy and water budgets. Aerosols, suspended in the atmosphere, interact with clouds and affect their properties. Recent studies have suggested that the aerosol effect on warm convective cloud systems evolve in time and eventually approach a steady state for which the overall effects of aerosols can be considered negligible. Using numerical simulations, it was estimated that the time needed for such cloud fields to approach this state is >24 hr. These results suggest that the typical cloud field lifetime is an important parameter in determining the total aerosol effect. Here, analyzing satellite observations and reanalysis data (with the aid of numerical simulations), we show that the characteristic timescale of warm convective cloud fields is less than 12 hr. Such a timescale implies that these clouds should be regarded as transient-state phenomena and therefore can be highly susceptible to changes in aerosol properties.