Profiler retrieved DSD evolution in the tropics and mid-latitudes

In precipitation conditions, VHF radars simultaneously detect echo from clear-air and hydrometeors. The precipitation echo is broadened through turbulence, and shifted due to the mean vertical air motion. Deconvolution of the clear-air and precipitation echoes results in a corrected precipitation spectrum, which can be converted to a size spectrum, and a drop size distribution (DSD) calculated. Examination of the evolution of the DSD through the fall from freezing level to ground, can then be used to infer the microphysical processes dominating the precipitation structure. In this study, VHF radars in the tropics and mid-latitudes have been used to compare DSD evolution. Variations associated with the very different melting level heights at two locations (Darwin and Adelaide) will be discussed.

The University of Adelaide operates a VHF Boundary Layer Profiler in Darwin, Australia. Data from this radar has been used to examine the evolution of the DSD in the tropics. Data was collected during the TWP-ICE campaign in January and February 2006, and has been classified as occurring under monsoon or break conditions, and sub-classified as stratiform or convective. The reflectivity, median drop diameter, rain rate, liquid water content and vertical velocity have been examined to infer dominant microphysical processes in each rain event.

In 2009, the University of Adelaide installed a VHF Boundary Layer profiler at its field site, Buckland Park, South Australia. A larger VHF Stratospheric-Tropospheric radar also operates at this site. This provides a unique opportunity to compare DSD retrievals on two co-located radars, but also to examine evolution of the DSD in the mid-latitudes. Data from Buckland Park have been classified as stratiform or convective, and dominant microphysical processes determined.

Results from Darwin will be presented, with particular emphasis on trends in DSD evolution through TWP-ICE. Results from both profilers in Adelaide will also be presented, with some discussion on differences in evolution between the tropics and mid-latitudes.