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Convective mass-flux from long term radar reflectivities over Darwin, Australia
  • Alessandro Carlo Maria Savazzi,
  • Christian Jakob,
  • Pier Siebesma
Alessandro Carlo Maria Savazzi
Delft University of Technology

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Christian Jakob
Monash University
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Pier Siebesma
TU Delft
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Most cumulus parametrizations today make use of a simple conceptual model of convection, called the mass-flux approach. This approach depicts convection as an ensemble of updrafts and downdrafts occurring within a model grid-box. The aim of this study is to determine convective mass-fluxes and their constituents on the scale of a 100 km GCM grid-box from a C-band polarimetric radar and thereafter investigate the relative role of area fraction and vertical velocity in determining the shape and magnitude of bulk mass-flux profiles. We make use of observational estimates of these quantities spanning 13 wet seasons in the tropical region of Darwin. Following a bulk approach, the results show that the distribution of mass-flux is positively skewed and its mean profile peaks at 4 km. This is the result of constant area fractions and increasing vertical velocities below that level. Above 4 km, in-cloud vertical velocity plays a marginal role compared to the convective area fraction in controlling mass-flux profiles.