Walter Scott, Jr. College of Engineering

Graduate Exam Abstract

Haonan Chen
M.S. Final
Jan 30, 2013, 2:30PM
Anatomy/Zoology E112
Quantitative Precipitation Estimation for An X-band Weather Radar Network
Abstract: Currently, the Next Generation (NEXRAD) radar
network, a joint effort of the U.S. Department of
Commerce (DOC), Defense (DOD), and Transportation
(DOT), provides radar data with updates every
five-six minutes across the United States. This
network consists of about 160 S-band (2.7 to 3.0
GHz) radar sites. At the maximum NEXRAD range of
230 km, the 0.5 degree radar beam is about 5.4 km
above ground level (AGL) because of the effect of
earth curvature. Consequently, much of the lower
atmosphere (1-3 km AGL) cannot be observed by the
NEXRAD. To overcome the fundamental coverage
limitations of today's weather surveillance
radars, and improve the spatial and temporal
resolution issues, the National Science Foundation
Engineering Center (NSF-ERC) for Collaborative
Adaptive Sensing of the Atmosphere (CASA) was
founded to revolutionize weather sensing in the
lower atmosphere by deploying a dense network of
shorter-range, low-power X-band dual-polarization
radars. The distributed CASA radars are operating
collaboratively to adapt the changing atmospheric
conditions. Accomplishments and breakthroughs
after five years operation have demonstrated the
success of CASA program.

Accurate radar quantitative precipitation
estimation (QPE) has been pursued since the
beginning of weather radar. For certain disaster
prevention applications such as flash flood and
landslide forecasting, the rain rate must however
be measured at a high spatial and temporal
resolution. To this end, high-resolution radar QPE
is one of the major research activities conducted
by the CASA community. A radar specific
differential propagation phase (Kdp)-based QPE
methodology has been developed in CASA. Unlike the
rainfall estimation based on the power terms such
as radar reflectivity (Z) and differential
reflectivity (Zdr), Kdp-based QPE is less
sensitive to the path attenuation, drop size
distribution (DSD), and radar calibration errors.
The CASA Kdp-based QPE system is also immune to
the partial beam blockage and hail contamination.

The performance of the CASA QPE system is
validated and evaluated by using rain gauges.
In CASA’s Integrated Project 1 (IP1) test bed in
Southwestern Oklahoma, a network of 20 rainfall
gauges is used for cross-comparison. 40 rainfall
cases, including severe, multicellular
thunderstorms, squall lines and widespread
stratiform rain, that happened during years 2007 -
2011, are used for validation and evaluation
purpose. The performance scores illustrate that
the CASA QPE system is a great improvement
compared to the current state-of-the-art.

In addition, the high-resolution CASA QPE products
such as instantaneous rainfall rate map and hourly
rainfall amount measurements can serve as a
reliable input for various distributed
hydrological models. The CASA QPE system can save
lived and properties from hazardous flash floods
by incorporating hydraulic and hydrologic models
for flood monitoring and warning.
Adviser: V. Chandrasekar
Co-Adviser: N/A
Non-ECE Member: Paul Mielke, Statistics
Member 3: Branislav Notaros
Addional Members: N/A
Please check with Haonan.Chen@ColoState.EDU for details.
Program of Study: