Microphysical, macrophysical, and radiative responses of subtropical marine clouds to aerosol injections

Abstract. Ship tracks in subtropical marine low clouds are simulated and investigated using large-eddy simulations. Five variants of a shallow stratocumulus-topped boundary layer (MBL) chosen to span range background aerosol concentrations variations free-tropospheric moisture. Idealized time-invariant meteorological forcings approximately steady-state constitute the conditions. We investigate processes controlling cloud microphysical, macrophysical, radiative responses injections. For analysis, we use novel methods decompose liquid water path (LWP) adjustment into changes boundary-layer properties effect (CRE) contributions from macro- microphysics. The key results that (a) cloud-top entrainment rate increases all cases, with stronger for thicker than thinner clouds; (b) drying warming induced by increased is offset differing degrees corresponding surface fluxes, precipitation, radiation; (c) MBL turbulence responds caused perturbation, this significantly affects macrophysics; (d) across 2 d simulation, were brightened cases. In pristine MBL, significant drizzle suppression injections not only greater retention but also intensification, leading increase amount. case, Twomey brightening strongly augmented an thickness cover. addition, reduction loss through coalescence scavenging more offsets dilution. This interplay precludes estimation lifetime perturbation. combined microphysics lead 10–100 times effective these cases relative those non-precipitating moderate polluted MBLs, enhancement makes drier, warmer, stratified, decrease thickness. LWP response greatest fraction moderately moist free troposphere. finding differs previous studies found larger drier troposphere, it initially clouds, so offsetting effects weaker. injected MBLs estimated be 2–3 d, which much longer estimates typical ship track lifetimes satellite images.