Aerosol Impacts on Convective Cold Pools in a Tropical Continental Environment

Convective cold pools and atmospheric aerosols both play important roles in convective organization and development. However, the ways in which atmospheric aerosols influence convective cold pools are not fully understood. This study addresses the question, how do atmospheric aerosols affect cold pool development in tropical continental convection? In particular, how do atmospheric aerosols affect cold pool size, strength, and thermodynamic structure? These questions are addressed by applying a cold pool identification and tracking algorithm to simulations performed using the open-source Regional Atmospheric Modeling System (RAMS).

RAMS was used to perform three high-resolution, day-long simulations of tropical sea-breeze convection. The domain size was 550 km × 200 km × 26 km, and the horizontal grid spacing was 1 km, with 57 vertical levels. In these simulations, two types of convection were observed: continental convection associated with diurnal heating, and convection generated by the sea breeze. The former type of convection is analyzed here. Each of the three simulations was performed with a different initial aerosol number concentration profile, and the aerosols were radiatively active. The clean, intermediate, and most polluted simulations were performed with surface (maximum) aerosol concentrations of 200 cm⁻³, 500 cm⁻³, and 2000 cm⁻³, respectively.

An ensemble of convective cold pools develops within each of the simulations. A new, unique cold pool identification algorithm is used to identify and analyze the convective cold pools. Each cold pool is treated as a separate cold pool “object”, and for each of the three simulations, the cold pools are averaged together to form a composite cold pool whose properties reflect the ensemble of convective cold pools.

It is found that the cold pools in the most polluted simulation are significantly weaker than those in the cleanest simulation, with smaller buoyancy depressions and less vigorous radial outflows. The cold pools in the most polluted simulation are correspondingly smaller than those in the cleanest simulation. The processes behind these results will be explored, and the implications for convective organization will be discussed.