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The marine-cloud brightening geoengineering technique has been suggested as a possible means of counteracting the positive radiative forcing associated with anthropogenic atmospheric CO₂ increases. The focus of this study is to quantify the albedo response to aerosols injected into marine stratocumulus cloud from a point source at different times of day. We use a cloud-resolving model to investigate both weakly precipitating and non-precipitating regimes. Injection into both regimes induces a first indirect aerosol effect. Additionally, the weakly precipitating regime shows evidence of liquid water path gain associated with a second indirect aerosol effect that contributes to a more negative radiative forcing, and cloud changes indicative of a regime change to more persistent cloud. This results in a cloud albedo increase up to six times larger than in the non-precipitating case. These indirect effects show considerable variation with injection at different times in the diurnal cycle. For the weakly precipitating case, aerosol injection results in domain average increases in cloud albedo of 0.28 and 0.17 in the early and mid morning (03:00:00 local time (LT) and 08:00:00 LT respectively) and 0.01 in the evening (18:00:00 LT). No cloud develops when injecting into the cloud-free early afternoon (13:00:00 LT). However, the all-sky albedo increases (which include both the indirect and direct aerosol effects) are highest for early morning injection (0.11). Mid-morning and daytime injections produce increases of 0.06, with the direct aerosol effect compensating for the lack of cloud albedo perturbation during the cloud-free early afternoon. Evening injection …