Walter Scott, Jr. College of Engineering

Graduate Exam Abstract

Minda Le
Ph.D. Preliminary
Aug 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