Vertical Motion Structure in Maritime continent mesoscale Convective Systems: Results from a 50-MHz Profiler

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  • 1 Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado
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Abstract

Wind profiler data wore used to determine the vertical motion structure in four tropical mcsoscale convective systems (MCSs), which occurred during the Down Under Doppler and Electricity Experiment (DUNDEE) near Darwin. Northern Territory, Australia. Three of the MCSs occurred during the monsoon-break convective regime and one occurred during the monsoon regime. In the break regime cases (each with a leading convective and trailing stratiform region structure), the wind profiler sampled low-level convective cells on the leading edge of the convective region, trailed by deeper updrafts of comparable magnitude. Surface rainfall measurements from a network of raingauges showed two comparable peaks in rainfall intensity that roughly corresponded to the passage of low-level and deep convective updraft (71%–80% of the system total rainfall was associated with the passage of the convective line). In the stratiform region, the profiler data showed generally weak vertical drafts (<1 m s−1) and the presence of both mesoscale upward and downward motion (17%–28% of the system total rainfall was associated with the passage of the stratiform region). Deep subsidence in the transition zone located between the convective and stratiform regions was also documented in each of the break regime cases. Composite vertical motion profiles in different regions of the break MCSs were constructed and the salient features of the profiles are described. The composite vertical motion profiles are compared to similar profiles from different graphical regions.

The evolution of the monsoon MCS was different from the break regime cases. This system was characterized by a series of convective updrafts embedded in stratiform cloud.

Abstract

Wind profiler data wore used to determine the vertical motion structure in four tropical mcsoscale convective systems (MCSs), which occurred during the Down Under Doppler and Electricity Experiment (DUNDEE) near Darwin. Northern Territory, Australia. Three of the MCSs occurred during the monsoon-break convective regime and one occurred during the monsoon regime. In the break regime cases (each with a leading convective and trailing stratiform region structure), the wind profiler sampled low-level convective cells on the leading edge of the convective region, trailed by deeper updrafts of comparable magnitude. Surface rainfall measurements from a network of raingauges showed two comparable peaks in rainfall intensity that roughly corresponded to the passage of low-level and deep convective updraft (71%–80% of the system total rainfall was associated with the passage of the convective line). In the stratiform region, the profiler data showed generally weak vertical drafts (<1 m s−1) and the presence of both mesoscale upward and downward motion (17%–28% of the system total rainfall was associated with the passage of the stratiform region). Deep subsidence in the transition zone located between the convective and stratiform regions was also documented in each of the break regime cases. Composite vertical motion profiles in different regions of the break MCSs were constructed and the salient features of the profiles are described. The composite vertical motion profiles are compared to similar profiles from different graphical regions.

The evolution of the monsoon MCS was different from the break regime cases. This system was characterized by a series of convective updrafts embedded in stratiform cloud.

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