Walter Scott, Jr. College of Engineering

Graduate Exam Abstract

Leonid Tolstoy
Ph.D. Preliminary
Apr 05, 2010, 3 pm
Engr E205
This is a preliminary exam
Abstract: Application of the Variational Method for Correction of Wet Ice
Attenuation for X-band Dual-Polarized Radar<br />
<br />
In recent years there has been a huge interest in the development and
use of dual-polarized radar systems operating at X-band (~10 GHz)
region of the electromagnetic spectrum. This is due to the fact that
these systems are smaller and cheaper allowing for a network to be
built, for example, for short range (typically < 30-40 km)
hydrological applications. Such networks allow for higher cross-beam
spatial resolutions while cheaper pedestals supporting a smaller
antenna also allows for higher temporal resolution as compared with
large S-band (long range) systems used by the National Weather
<br /><br />
Dual-polarization radar techniques allow for correction of the strong
attenuation of the electromagnetic radar signal due to rain at X-band
and higher frequencies. However, practical attempts to develop
reliable correction algorithms have been cumbered by the need to deal
with the rather large statistical fluctuations or “noise” in the
measured polarization parameters. Recently, the variational method was
proposed, which overcomes this problem by using the forward model for
polarization variables, and uses iterative approach to minimize the
difference between modeled and observed values, in a least squares
sense. This approach also allows for detection of hail and
determination of the fraction of reflectivity due to the hail when the
precipitation shaft is composed of a mixture of rain and hail. It was
shown that this approach works well with S-band radar data.

The purpose of this research is to extend the application of the
variational method to the X-band dual-polarization radar data. The
main objective is to correct for attenuation caused by rain mixed with
wet ice hydrometeors (e.g., hail) in deep convection. The standard
dual-polarization method of attenuation-correction using the
differential propagation phase between H and V polarized waves cannot
account for wet ice hydrometeors along the propagation path. The
ultimate goal is to develop a feasible and robust variational-based
algorithm for rain and hail attenuation correction for the Collaborate
Adaptive Sensing of the Atmosphere (CASA) project.
Adviser: Dr. Viswanathan N Bringi
Co-Adviser: Dr. V. Chandrasekar
Non-ECE Member: Dr. Christian D Kummerow (Atmospheric Science)
Member 3: Dr. Branislav Notaros
Addional Members: N/A
Program of Study: