Abstract

This study explores primarily the coupling of dynamical and microphysical processes involving both natural and anthropogenic particles over the Bay of Bengal. The vertical transport of sea spray to cloud bases is first quantified from measurements. Sea salt aerosol distributions are then incorporated into a detailed chemical parcel model accounting for strong non-linear effects in concentrated droplets which subsequently grow to form much larger raindrops through a process of stochastic coalescence.

The second part of the study focuses on the effect of millimeter-scale vortices obtained during both stormy as well non-stormy days on the quantification of rain rates. In essence, rescaled settling of the small inertial particles (mainly the film mode drops) is obtained as they are centrifuged out of vortices and eddies in turbulence. This process enhances the average sedimentation rate of particles lying below a critical radius (~ 20 microns) by about 80% strongly impacting rain rates. Whilst earlier studies have shown that multicomponent mixtures perturb the AerosolŠ\Cloud Droplet relationships over certain regimes; this first study shows that when multiple aerosol modes are present within convective clouds, another added perturbing effect ¨the enhanced settling rates from the centrifuging action of the microscale eddies increases precipitation rates over the Bay of Bengal.

Wider implications are also discussed including recent new calculations on the mass accommodation of condensable vapours on an assortment of particle size distributions.