Development of NEXRAD Wind Retrievals as Input to Atmospheric Dispersion Models

Abstract

SummaryTwo techniques that derive spatially varying wind fields from operational radar measurements have been evaluated in this study. Based on results, we propose that one technique be implemented operationally in a phased approach. The other technique would be suitable for operational implementation only after additional modifications have been made and evaluated. These two techniques would require additional funding to implement, maintain operational versions of these codes, and perform additional research to improve their accuracy.Atmospheric dispersion models (ADMs) are used by emergency-response organizations to address the consequences of potential airborne releases of harmful materials. The wind fields in ADMs are based on meteorological measurements and forecasts made by atmospheric models. In the United States, routine meteorological measurements from surface stations, towers, rawinsondes, and radar wind profilers are available to drive ADMs. Large metropolitan areas usually have a network of surface stations; however, the wind-speed and direction measurements from these stations are usually not representative of conditions above the surface. There are currently relatively few measurements that can characterize the winds above the surface. One potentially rich, yet untapped, source of meteorological data for routine use in ADMs is from the Next Generation Weather Radar (NEXRAD) systems with 141 nearly identical WSR-88D Doppler radar units installed throughout the United States.The objective of this study is to determine the feasibility that routinely collected data from the Doppler radars can appropriately be used in ADMs for emergency response. We have evaluated the computational efficiency and accuracy of two variational mathematical techniques that derive the u-and v-components of the wind from radial velocities obtained from Doppler radars. A review of the scientific literature indicated that the techniques employ significantly different approaches in applying the variational techniques: 2-D Variational (2DVar), developed by the National Oceanic and Atmospheric Administration's National Severe Storms Laboratory and Variational Doppler Radar Analysis System (VDRAS), developed by the National Center for Atmospheric Research. We designed a series of numerical experiments in which both models employed the same horizontal domain and resolution encompassing Oklahoma City for a 2-week period during the summer of 2003 so that the computed wind retrievals could be fairly compared. Both models ran faster than real-time on one typical dual-processor computer, indicating that they could be used to generate wind retrievals in near real-time. The simpler approach of 2DVar allowed it to execute ~2.5 faster than VDRAS. The simpler approach of 2DVar allowed it to execute ~2.5 times faster than VDRAS.The accuracy of 2DVar and VDRAS is quantified by comparing the derived wind components with independent, meteorological measurements made by radar wind profilers. Both systems qualitatively reproduced the observed diurn...

Wind Energy Instrumentation Atlas

“…Like lidar, radar exploits the Doppler effect: a short pulse of energy is emitted from a radar, and when the pulse strikes an object, the backscattered energy is measured to identify the object, its location, and how it is moving along the direction of the radar beam. A network of Next Generation Radar (NEXRAD) systems provides precipitation and wind observations across the United States, but the resolution of the winds and accuracy of the wind retrievals do not offer the same benefits as typical instrumentation like radar wind profilers (Fast et al 2007) and are not generally considered useful for wind energy applications.…”