  Atmospheric water vapour is an essential ingredient of weather and climate.
Key features of its distribution can be represented by kinematic models which
treat it as a passive scalar advected by a prescribed flow and reacting through
condensation. Condensation acts as a sink that maintains specific humidity
below a prescribed, space-dependent saturation value. In order to investigate
how the interplay between large-scale advection, small-scale turbulence and
condensation controls the moisture distribution, we develop simple kinematic
models which combine a single circulating flow with a Brownian-motion
representation of turbulence. We first study the drying mechanism of a
water-vapour anomaly released inside a vortex at an initial time. Next, we
consider a cellular flow with a moisture source at a boundary. The
statistically steady state attained shows features reminiscent of the Hadley
cell such as boundary layers, a region of intense precipitation and a relative
humidity minimum. Explicit results provide a detailed characterisation of these
features in the limit of strong flow.
