Rigorous attempts have not yet been made to investigate the range of microphysical characteristics of supercell thunderstorms. The overarching goal of this research was to i) deploy six mobile disdrometers within supercell thunderstorms during the second Verification of the Origins of Rotation in Tornadoes EXperiment (VORTEX2) in 2010, ii) conduct a comprehensive analysis of all disdrometer observations to determine microphysical characteristics in tornadic compared to nontornadic supercell thunderstorms, and iii) relate the results to high-resolution polarimetric Doppler radar observations. While recent analyses of disdrometers and polarimetric radar observations have provided some insights about hydrometeor types within supercell thunderstorms, a comprehensive analysis of a number of cases using high-resolution measurements has yet to be established. The specific objective of the research proposed herein is to analyze particle size distribution, fall velocity, and surface observations in conjunction with dual-polarization Doppler radar measurements during Radar Observations of Tornadoes and Thunderstorm Experiment (ROTATE) 2008 and VORTEX2 to i) characterize PSD and fall velocities in different areas of the storm and at various lifetimes of supercell thunderstorms, ii) create a PSD-parameter data base for understanding microphysical processes within supercell thunderstorms and evaluating storm-scale numerical model outputs, and iii) studying steady-state and intermittent microphysical processes relevant for ice production and determine the effect of the evaporative cooling between tornadic and nontornadic storms by additionally analyzing 3-dimensional dual-polarization and dual-Doppler radar data.

Major findings related to the data analysis of the VORTEX2 2009 and 2010 data can be summarized as followed: i) Surface disdrometer observations can be used to validate the performance of a differential phase-based attenuation correction scheme that is applied to data recorded by the National Oceanic and Atmospheric Administration’s (NOAA), X-band, dual-Polarized (NOXP) mobile radar. Disdrometer observations can be used to quantify the attenuation-corrected radar reflectivity, which is particularly useful for X-band radar observations in thunderstorms (Kalina et al. 2014a). ii) Raindrop-size distributions were used to study particle size-sorting and microphysical processes in thunderstorms. The study revealed that the raindrop size distribution changes rapidly in time and space in convective thunderstorms. Graupel, hailstones, and large raindrops were primarily observed close to the updraft region of thunderstorms in the forward- and rear-flank downdrafts and in the reflectivity hook appendage. Close to the updraft, large raindrops were usually accompanied by an increase in small-sized raindrops (Friedrich et al. 2013a). iii) Strong winds affect the quality of optical PARSIVEL disdrometer measurements, which is characterized by a large number concentration of raindrops with large diameters (> 5 mm) and unrealistic fall velocities (< 1 m s^-1). It is correlated with high wind speeds, and is consistently observed by stationary disdrometers but is not observed by articulating disdrometers (instruments whose sampling area is rotated into the wind). Most of the time, this effect occurs when wind speed exceeds 20 m s^-1, although it was also observed when wind speed was as low as 10 m s^-1 (Friedrich et al. 2013b). iv) Idealized high-resolution (1 km) supercell simulations using the Weather Research and Forecasting Model (WRF) were used to analyze the affect of aerosol concentration and drop breakup on cold pool, drop size distribution, collision and coalescence, and the updraft/downdraft in supercell thunderstorms. The results indicate that the maximum perturbation in the microphysical process rates (relative to the c...

Please report errors in award information by writing to: awardsearch@nsf.gov.