My overall research goal is to understand the integrated kinematic, microphysical and electrical nature of clouds and precipitation systems. My research approach is primarily observational in nature. Although I use a wide variety of observational platforms, radar remote sensing is my primary tool for diagnosing the structure, kinematics and microphysics of clouds and precipitation. I employ multi-Doppler and dual-polarimetric observations and analysis techniques to diagnose the three-dimensional (3-D) wind field and hydrometeor types and amounts. I use both centimeter (S-, C- X-, and Ku-band) and millimeter (such as W-band) wavelength radars to study precipitation and clouds, respectively. Over the last 18 years, I have worked closely with a number of polarimetric radars, including the ARMOR, MAX, SMART, NCAR SPOL, CSU-CHILL, BMRC CPOL, NASA NPOL, K-Pol, and UWY WCR radars. I have served as radar or mission scientist, including lead, on a number of NASA and NSF funded international field campaigns using these radars. To achieve my goals, I have developed several dual-polarimetric radar algorithms designed to improve data quality, including the mitigation of attenuation, calibration bias, and beam blocking errors, and to better estimate precipitation rate and identify hydrometeor type.
A key objective for our research team, which includes a number of UAHuntsville graduate students and staff and NASA MSFC scientists, is to improve the representation of cloud precipitation and dynamical processes within various models, including cloud resolving models (CRMs) and numerical weather prediction (NWP) models. Better knowledge of precipitation properties, such as the 3-D distribution of types, sizes and amounts, are also important for constraining the parameterizations used by a wide variety of applications, including satellite remote sensing algorithms in the NASA Global Precipitation Measurement Mission (GPM/PMM) and missile erosion models employed by the Department of Defense (DoD). In addition to ground- and satellite-based radars, we have utilized surface-based (disdrometers, rain gauges) and aircraft in-situ precipitation measurement instruments to achieve these goals.
Another central purpose of our UAHuntsville-NASA MSFC research team is to improve the short-term prediction of high impact weather events that adversely affect public safety and economic productivity. Severe weather applications include lightning, tornadoes, hail storms, flash flooding, microbursts, hurricanes, and aircraft icing and turbulence. We have studied high impact weather in supercells, multicell convection, tropical and mid-latitude Mesoscale Convective Systems (MCSs), hurricanes, and non-precipitating mixed-phase clouds. Our dual-polarimetric radar research efforts in quantitative precipitation estimation (QPE) are being used in a wide variety of applications including improved hydrologic modeling and river management by the Tennessee Valley Authority (TVA) and soil water and evapo-transpiration modeling by NASA MSFC. Our NASA, NOAA and NSF funded physical process studies employing dual-polarimetric hydrometeor identification algorithms are leading to improved diagnosis and short-term prediction of lightning potential, severe hail, tornadoes and straight line winds.
Using radar and a variety of lightning sensors (such as the NASA TRMM Lightning Imaging Sensor (LIS) and the NASA MSFC Lightning Mapping Array (LMA)), we have studied cloud electrification and lightning in a wide variety of thunderstorm types, including ordinary convection, multicell squall lines, hail storms, supercells (tornadic and non-tornadic), and MCSs. Lightning applications funded by NASA MSFC, NASA LIS, NOAA CSTAR, NOAA GOES-R and NSF include the forecasting of lightning initiation and cessation, cloud electrification mechanisms, and the use of lightning in the short-term prediction of high impact convective weather, including severe weather and aviation hazards.