Graduate Exam Abstract

Minda Le

Ph.D. Preliminary
August 26, 2011, 3:00-6:00pm
To be Announced
Microphysical Retrieval and profile classification for GPM Dual-frequency Precipitation Radar and the Ground Validation

Abstract: ABSTRACT The Global Precipitation Measurement (GPM) mission is planned to be the next satellite mission to obtain global precipitation measurements jointed by National Aeronautic and Space Administration (NASA) of USA and the Japanese Aerospace Exploration Agency (JAXA). The core satellite will be equipped with a dual frequency precipitation radar (DPR) operating at Ku (13.6 GHz) and Ka (35.5 GHz) band with the capability to cover 65 latitude of the earth. One primary goal of the DPR is to improve accuracy in estimation of drop size distribution (DSD) parameters of precipitation. The estimation of the DSD parameters of precipitation particles helps to achieve more accurate estimation of precipitation rate. The DSD is also centrally important in the determination of the electromagnetic scattering properties of precipitation media. The combination of data from the two channels, in principle, can provide more accurate estimates of DSD parameters than the Tropical Rainfall Measurement Mission Precipitation radar (TRMM PR) with Ku band channel only. The research reported here develops a hybrid method to retrieve DSD parameters from DPR. The evaluation is based on simulation data from airborne precipitation radar which emulates what GPM-DPR will see. Precipitation type classification is a critical module in the microphysical retrieval system for GPM-DPR. The nature of microphysical models and equations to use in the DSD retrieval algorithm are determined by the precipitation type of each profile and the phase state. In the GPM era, Ka band channel enables the detection of light rain or snowfall in the mid- and high- latitudes compared to the TRMM PR (Ku band only).DPR offers dual-frequency observations (Z_h (K_u ) and Z_h (K_a )) along the vertical profile. This allows us to investigate the microphysical properties using the difference between two frequency observations (or DFRm=Zh (Ku)-Zh (Ka)). DFRm is also called the measured dual frequency ratio. Both non-Rayleigh scattering effects and attenuation difference control the shape of the vertical profile of DFRm. Its pattern is influenced by both rain and ice part of precipitation and also both the forward scatter and back scatter of the scattering mechanism. Therefore, DPR could provide better performance in precipitation type classification and hydrometeor identification than TRMM PR. The research reported here develops a potential module to perform profile classification for GPM-DPR using DFRm profile and its range variability. Ground validation is an integral part of all satellite precipitation missions. Similar to TRMM, the GPM validation falls in the general class of validation and integration of information from a variety of space-borne observing platforms with ground-based measurements. Dual polarization ground radar is a powerful tool that can be used to address a number of important questions that arise in the validation process, especially those associated with precipitation microphysics and algorithm development. Extensive research has also been done regarding accurate rain DSD retrieval as well as attenuation correction for dual- polarization ground radar operating at S-, C- and X- band by using polarimetric measurements. However, polarimetric ground radar operating at a single frequency channel has limitation on DSD retrieval beyond rain region. A dual frequency and dual polarization ground radar operating at the same frequency channels as GPM-DPR is being built. The research reported here develops an algorithm to retrieve DSD for this dual frequency and dual polarization ground radar which will serve as GPM DPR ground validation.

Adviser: Dr. V. Chandrasekar
Co-Adviser: N/A
Non-ECE Member: Dr. Paul Mielke
Member 3: Dr. Anura Jayasumana
Addional Members: Dr. Branislav Notaros

[1]V. Chandrasekar, Direk, Khajonrat, and Minda ,Le (2008): Tropical Cyclone Nargis over Myanmar: Vertical structure and Microphysics based on Space-based Radar observations, Proc IEEE IGARSS’08, Boston. [2]M. Le, V. Chandrasekar, S.Lim (2009): Combined Ku and Ka band observations of precipitation and retrievals for GPM ground validation, Proc IEEE IGARSS’09, South Africa. [3]M. Le, V. Chandrasekar, S.Lim (2009): Microphysical retrieval from dual-frequency GPM observations, 34th Conf on Radar Meteorology. Amer. Meteor. Soc., Williamsburg, VA, Oct. [4]M. Le and V. Chandrasekar (2010): Dual frequency and dual polarization radar observations of precipitation and retrievals for GPM ground validation. Proc USNC-URSI ’10, Boulder, Colorado. [5]M. Le, V. Chandrasekar and S. Lim (2010): Microphysical retrievals of dual polarization and dual frequency ground radar for GPM ground validation. Proc IEEE IGARSS’10, Hawaii. [6]M. Le, V. Chandrasekar and S. Lim (2010): Microphysical retrieval from dual frequency precipitation radar board GPM. Proc IEEE IGARSS’10, Hawaii. [7]M. Le and V. Chandrasekar (2011): Precipitation type and profile classification for GPM-DPR. Proc IEEE IGARSS’11, Vancouver, Canada. [8]V. Chandrasekar and Minda, Le (2011): Global retrieval of drop size distribution: Past, Present and Future. Proc IEEE IGARSS’11, Vancouver, Canada. [9]M. Le and V. Chandrasekar (2011): Rain drop size distribution retrieval from dual frequency and dual polarization radar. Accepted by IEEE Trans. Geosci. Remote Sensing

Program of Study:
ECE 512
ECE 742
EE 549
EE 672-001
EE 795
ECE 641
ECE 642