Jennifer F. Newman

Range-Correcting Azimuthal Shear in Doppler Radar Data

AbstractThe current tornado detection algorithm (TDA) used by the National Weather Service produces a large number of false detections, primarily because it calculates azimuthal shear in a manner that is adversely impacted by noisy velocity data and range-degraded velocity signatures. Coincident with the advent of new radar-derived products and ongoing research involving new weather radar systems, the National Severe Storms Laboratory is developing an improved TDA. A primary component of this algorithm is the local, linear least squares derivatives (LLSD) azimuthal shear field. The LLSD method incorporates rotational derivatives of the velocity field and is affected less strongly by noisy velocity data in comparison with traditional “peak to peak” azimuthal shear calculations. LLSD shear is generally less range dependent than peak-to-peak shear, although some range dependency is unavoidable. The relationship between range and the LLSD shear values of simulated circulations was examined to develop a range ...

Strengths and Limitations of Current Radar Systems for Two Stakeholder Groups in the Southern Plains

Advancements in radar technology since the deployment of the Weather Surveillance Radar-1988 Doppler (WSR-88D) network have prompted consideration of radar replacement technologies. In order for the outcomes of advanced radar research and development to be the most beneficial to users, an understanding of user needs must be established early in the process and considered throughout. As an important early step in addressing this need, this study explored the strengths and limitations of current radar systems for nine participants from two key stakeholder groups: NOAAs NWS and broadcast meteorologists. Critical incident interviews revealed the role of each stakeholder group and attained stories that exemplified radar strengths and limitations in their respective roles. NWS forecasters emphasized using radar as an essential tool to assess the current weather situation and communicate hazards to key stakeholder groups. TV broadcasters emphasized adding meaning and value to NWS information and using radar to ...

Evolution of a Quasi-Linear Convective System Sampled by Phased Array Radar

AbstractOn 2 April 2010, a quasi-linear convective system (QLCS) moved eastward through Oklahoma during the early morning hours. Wind damage in Rush Springs, Oklahoma, approached (enhanced Fujita) EF1-scale intensity and was likely associated with a mesovortex along the leading edge of the QLCS. The evolution of the QLCS as it produced its first bow echo was captured by the National Weather Radar Testbed Phased Array Radar (NWRT PAR) in Norman, Oklahoma. The NWRT PAR is an S-band radar with an electronically steered beam, allowing for rapid volumetric updates (~1 min) and user-defined scanning strategies. The rapid temporal updates and dense vertical sampling of the PAR created a detailed depiction of the damaging wind mechanisms associated with the QLCS. Key features sampled by the PAR include microbursts, an intensifying midlevel jet, and rotation associated with the mesovortex. In this work, PAR data are analyzed and compared to data from nearby operational radars, highlighting the advantages of using ...

Evaluation of the effect of Realistic and Synthetic Inflow on the Power and Loading Pattern of Wind Turbine

This study is focused on investigating the differences between realistic and synthetic inflow models for the large eddy simulation (LES) of the flow field and prediction of aerodynamics in an onshore and offshore wind farm . Weather Research and Forecasting (WRF) is run in LES mode for generating the realistic inflow boundary conditions while synthetic inflow is generated using Mann’s model. WindPact and NREL 5MW turbines were used as the model turbines for onshore and offshore wind farms, respectively. The geostropic wind driving the flow field in WRF-LES was adjusted to ensure the same wind speed at hub height for onshore and offshore cases, respectively to perform a comparative study. The coupling between the mesoscale and microscale codes are performed using a mesoscale microscale coupling interface (MMCI) developed as a part of our earlier work. This framework allows the efficient interpolation of data between the different codes in an automated and parallel fashion. Three different microscale computational fluid dynamics codes were