Vertical motion structure in tropical mesoscale convective systems

VHF wind profiler data were used to study the vertical draft structure within 13 tropical Mesoscale Convective Systems (MCSs) near Darwin, Australia during two consecutive wet seasons. Single-Doppler radar and surface rainfall data were also utilized in order to correlate the reflectivity and surface rainfall patterns with the structure of the vertical air motion measured by the wind profiler. Because of Darwin's unique location at the southern tip of the Maritime Continent, the wind profiler was able to observe vertical drafts in both the monsoon (maritime) and monsoon break (continental) convective regimes.; The break regime MCSs (6 total) were all squall lines, characterized by a leading line of convection with intense precipitation and sharp horizontal reflectivity gradients, as well as a trailing stratiform region with relatively small horizontal reflectivity gradients and light rainfall. In contrast, the monsoon systems (7 total) were characterized as relatively unorganized regions of stratiform cloud with embedded convective bands which moved on-shore in the monsoon flow. Results from the Darwin rain gauge network indicated that the vast majority of the total rainfall in each monsoon and break MCS was associated with the convective portion of the system, in contrast to previous studies of MCSs in other tropical locations.; The break regime MCSs were all characterized by a consistent low-level updraft peak associated with convective cells on the leading edge of each squall line, trailed by deeper convective updrafts in the upper troposphere. A significant fraction of the convective rainfall was associated with the low-level updraft indicating that warm rain collision-coalescence processes were important to precipitation production. In the monsoon regime, the convective region vertical air motions were typically less than the squall lines in the lower troposphere but larger in the upper troposphere. The low-level differences are consistent with the smaller virtual temperature excess in the monsoon soundings, as well as the larger vertical radar reflectivity gradients observed in monsoon convection.; Consistent with the differences in vertical air motion patterns, diabatic heating and moistening profiles showed that the monsoon MCSs were characterized by a higher level peak heating and drying compared to the break MCSs.