Graduate Exam Abstract
Renzo BechiniPh.D. Preliminary
September 11, 2013, 2.30pm
Microphysics and dynamics retrievals from dual-polarization radar for very short-term forecasting
Abstract: Nowcasting is primarily a description of the current atmospheric state and the near-future forecasted state, therefore relying heavily on observations. Besides routine meteorological observations (pressure, temperature, humidity, wind), dual-polarization weather radar provides a large amount of useful information due to the frequent-update (~5 min) and high-resolution (~500 m) three-dimensional sampling of the atmosphere. However, radar remote observations are not directly related to the atmospheric state variables, which implies a complexity in the numerical model data assimilation. This problem is normally dealt with by defining observation operators to simulate the radar variables from the model state vector.
The dual-polarization radar observations are analyzed in order to demonstrate their potential for microphysics and dynamics retrievals. Hydrometeor classification algorithms, dual-polarization analyses of signatures in convective storms and in stratiform ice clouds are developed towards this goal. It is found that specific dual-polarization radar signatures can be successfully related to important dynamic properties such as vertical air motions, both in convective precipitation (strong updrafts, several m/s) and in stratiform precipitation (large areas of weak updrafts, tenths of m/s, associated with mid-tropospheric mesoscale forcing).
In particular the relevance of a well-known dual-polarization feature ("vertical columns of differential reflectivity") associated with deep convection is shown by including the microphysics (and dynamics-related) information into an analysis of the surface winds. The significance of the results prompts for the development of a novel way to assimilate dual-polarization radar observations in current numerical model variational assimilation schemes.
Adviser: V. Chandrasekar
Non-ECE Member: Paul Mielke, Statistics
Member 3: Branislav Notaros, ECE
Addional Members: Anura Jayasumana, ECE
Polarimetric Radar Observations in the Ice Region of Precipitating Clouds at C-Band and X-Band Radar Frequencies
R. Bechini, L. Baldini, V. Chandrasekar
Journal of Applied Meteorology and Climatology
Volume 52, Issue 5 (May 2013) pp. 1147-1169
Program of Study: