Drop size distribution retrievals during TWPICE

This research is largely concerned with the improvement of quantitative rainfall estimates, in order to improve short-term weather forecasting, using VHF radar. VHF radars are capable of retrieving drop size distributions (DSD's), and will be used to describe the vertical and temporal distribution of DSD's, in order to improve quantitative rainfall estimates. This will then assist forecasters in tracking rapidly evolving weather events which have the potential to cause severe wind, hail and flood damage.

The first stage was participation in the Tropical Warm Pool International Cloud Experiment (TWPICE) which occurred in Darwin and surrounding areas in January and February 2006. The campaign presented a unique opportunity to compare air space sampled by both a VHF wind profiler owned by the University of Adelaide Atmospheric Physics group, and the Bureau's C-Pol weather radar. We are using this arrangement as a basis for refining the drop size distribution retrieval technique before applying it in stage two in Adelaide.

The Australian Bureau of Meteorology recently installed a weather-watch radar at Buckland Park, South Australia, a field site belonging to the University of Adelaide, located 40km north of the city. This presents a similar situation to that in Darwin where part of the air space sampled by this radar covers the Adelaide airport where the University of Adelaide Atmospheric Physics group has a VHF wind profiling radar. When data from both sets has been collected they will be compared as there is evidence of variation in the drop size distributions and their evolution in altitude in mid – latitudes, as compared to the tropics. Our two data sets will provide a mechanism for investigating the evolution of DSD's in height, and how this relates to cloud characteristics. This in turn will lead to an improved understanding of the use of weather radar for quantitative rainfall estimation.

Several rain events from the TWPICE period, both stratiform and convective will be presented. These will be looked at in detail to consider spatial and temporal evolution of DSD's, and parameters calculated from the retrieval such as rain rate and liquid water content. Retrievals will be presented from both the VHF and C-Pol radars, to validate the retrieval technique.