Vertical motions of the tropical convective cloud spectrum over Darwin, Australia
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2015 Royal Meteorological Society. Three months of profiler observations from Darwin, Australia are separated into seven cloud types (shallow, mid-level, and deep convective; weak and robust stratiform rain; and transitional and ice-only anvil) to provide vertical velocity statistics on the full spectrum of tropical convective clouds over the course of a monsoon season. Consistent with past studies, convective updraughts increase in height and magnitude as the convective cloud height increases. Shallow/mid-level/deep convection has a mean maximum value of 0.3 m s-1 at 3 km/0.6 m s-1 at 5 km/2.5 m s-1 at 8 km. Deep convective extremes approach 18 m s-1 above 8 km while downdraughts in all convective cloud types are maximum below 4 km. Stratiform vertical velocities are weaker and less varied than in active convection, with maximum mean values <0.25 m s-1. However, stratiform rain regions associated with larger near-surface reflectivities (and thus rain rates) have stronger mesoscale up- and downdraughts than weaker stratiform rain regions. Anvil cloud with little or no rain near the surface also exhibits mesoscale up- and downdraughts, but the vertical velocity profile is shifted up in height by at least 2 km. In addition, anvil updraughts were only 20-50% of the magnitudes in the stratiform rain region. Overall, the vertical motion statistics were similar across the pre-, active and suppressed monsoon periods. The vertical velocity distributions for each cloud type were also generally consistent with the reflectivity distributions (i.e. the strongest updraughts were often linked to the largest reflectivities), allowing for some linkages between the dynamical and microphysical cloud properties. For example, strong updraughts above the 0 C level in deep convection are associated with strongly sloping reflectivity profiles supporting the importance of cold rain growth processes, and stronger vertical motions are associated with stratiform rain that has a robust bright band.
