  We present a novel laboratory experiment, boiling stratified flow, as an
analogy for atmospheric moist convection. A layer of diluted syrup is placed
below freshwater in a beaker and heated from below. The vertical temperature
profile in the experiment is analogous to the vapor mixing ratio in the
atmosphere while the vertical profile of freshwater concentration in the
experiment is analogous to the potential temperature profile in the atmosphere.
Boiling starts when the bottom of the syrup layer reaches the boiling point,
producing bubbles and vortex rings that stir the two-layer density interface
and bring colder fresh water into the syrup layer. When the syrup layer at the
beginning of the experiment is sufficiently thin and diluted, the vortex rings
entrain more cold water than needed to remove superheating in the syrup layer,
ending the boiling. When the syrup layer is deep and concentrated, the boiling
is steady since the entrained colder water instantaneously removes the
superheating in the bottom syrup layer. A theory is derived to predict the
entrainment rate and the transition between the intermittent and steady boiling
regimes, validated by experimental data. We suggest that these dynamics may
share similarities with the mixing and lifecycle of cumulus convection.
