Precipitation microphysics and vertical air motions retrieved from VHF, UHF, and S-band profilers during TWPICE

The Tropical Warm Pool International Cloud Experiment (TWPICE) was held in and around Darwin, Australia, from mid-January through mid-February 2006. An overarching goal of the experiment was to observe, describe, and understand monsoon cloud structure, their evolution, and their impact on the environment. To achieve this goal, the experiment used a combination of six craft, a network of radiosonde stations, satellite observations, and ground based radiometers, scanning and vertically pointing radars. The scanning radars provide information on the horizontal structure of the precipitating cloud systems and the vertically pointing profiling radars provided detailed information on the vertical structure and temporal variability of the vertical air motion and the precipitation in the different phases of the monsoon rain as the precipitation events pass directly over the profiler site.

During TWPICE, three profilers were collocated and operated at 50 MHz (VHF), 920 MHz (UHF), and 2835 MHz (S-band). By analyzing the Doppler velocity spectra, the vertical air motion can be estimated using the VHF profiler observations and the raindrop size distribution (DSD) can be estimated using the UHF and S-band profiler observations. When retrieving the DSD from profiler observations, uncertainties in the retrieval are introduced by the analysis methodology and by the assumed functional form of the DSD (for example, exponential, gamma, or log-normal). Examples of different analysis methodologies include comparing a convolved model spectrum to the observed spectrum or performing a deconvolution on the observed spectrum and comparing it to the model spectrum.

To overcome the uncertainties associated with each analysis methodology and the assumed DSD functional form, an ensemble approach has been developed which combines the DSD retrievals from over 25 different models. The ensemble approach yields ensemble DSD parameters and vertical air motion estimates with their uncertainties that can be provided to modelers for the next step in understanding the microphysical processes in precipitating systems. Results from the ensemble approach will be presented using observations from TWPICE which included intense convective events with updrafts exceeding 20 m/s as well as stratiform rain events.