6B.3 ADAPTS IMPLEMENTATION: CAN WE EXPLOIT PHASED-ARRAY RADAR’S ELECTRONIC BEAM STEERING CAPABILITIES TO REDUCE UPDATE TIMES? Sebastián Torres, Pam Heinselman, Ric Adams, Christopher Curtis, Eddie Forren, Igor Ivić, David Priegnitz, John Thompson, and David Warde Cooperative Institute for Mesoscale Meteorological Studies, The University of Oklahoma and NOAA/OAR National Severe Storms Laboratory Norman, Oklahoma 1. INTRODUCTION It is well understood that high-temporal resolution data has the potential to improve the understanding, detection, and warning of hazardous weather phenomena. In fact, in a 2008 survey about scanning strategy improvements conducted by the US National Weather Service, 62% of forecasters indicated the need for faster updates. One of the strongest advantages of using phased-array radars for weather observations is their potential to produce data with very high temporal resolution. Naturally, this has been a major research and development thrust on the National Severe Storms Lab’s (NSSL) National Weather Radar Testbed Phased- Array Radar (NWRT PAR). One way to get faster updates without loss in data quality is by adaptively focusing observations to the regions of interest. This is the purpose of the Adaptive DSP Algorithm for Timely Scans (ADAPTS), which was first demonstrated in 2009. ADAPTS works by activating or deactivating individual beam positions within a scanning strategy based on elevation, significance, and neighborhood criteria. Preliminary evaluations of ADAPTS showed significant time savings, but also helped identify areas for further improvement. This paper describes the initial implementation of ADAPTS, its recent evolution, and outlines a plan for future enhancements towards obtaining the best weather observations in the shortest amount of time. 2. THE NATIONAL WEATHER RADAR TESTBED PHASED ARRAY RADAR (NWRT PAR) In a nutshell, the NWRT PAR exploits a passive, 4352-element phased-array antenna to provide stationary, two-dimensional electronic scanning of weather echoes within a given 90° azimuthal sector. The antenna is mounted on a pedestal so that the best orientation can be selected prior to any data collection. The antenna beamwidth is 1.5° at boresite (i.e., perpendicular to the array plane) and gradually increases to 2.1° at ±45° from boresite. The peak transmitted power is 750 kW and the range resolution provided by this system is 240 m. In some aspects, such as beamwidth and sensitivity, the NWRT PAR is inferior compared to operational radars such as the Corresponding author address: Sebastian M. Torres, NSSL, 120 David L. Boren Blvd., Norman, OK 73072; email: Sebastian.Torres@noaa.gov Weather Surveillance Radar-1988 Doppler (WSR-88D). However, the purpose of this system is not to achieve operational-like performance or to serve as a prototype for the replacement of WSR-88D radars, but to demonstrate the operational utility of some of the unique capabilities offered by PAR technology that may eventually drive the design of future operational weather radars (Zrnić et al. 2007). Significant hardware, software infrastructure, and signal processing upgrades have been accomplished to support the NWRT mission as a demonstrator system for the MPAR concept. The deployment of a new signal processing hardware (Forsyth et al. 2007) marked the beginning of a series of engineering upgrades. Using a path of continuous software development with an average of two releases every year, new and improved capabilities have been made available on the NWRT PAR (Torres et al. 2009, 2010, 2011). The need for these improvements is twofold. On one hand, it is desirable that the NWRT PAR produces operational-like data with quality comparable to that of the WSR-88D. High data quality leads to better data interpretation and is conducive to the development of effective automatic algorithms. On the other hand, improvements are needed to demonstrate new capabilities, some of which are applicable to both conventional and PAR, and some that are unique or better suited to PAR. A prime example of the latter is the use of adaptive scanning strategies to perform focused observations of the atmosphere, which is the focus of this work. Whereas adaptive scanning is not unique to PAR, update times can be greatly reduced by using PAR’s electronic beam steering capabilities because scanning strategies are not constrained by the inherent mechanical inertia of reflector antennas. The rest of the paper describes the initial implementation, present state, and future plans for adaptive scanning on the NWRT PAR. 3. ADAPTIVE DSP ALGORITHM FOR PHASED- ARRAY RADAR TIMELY SCANS (ADAPTS) Fast adaptive scanning with the NWRT PAR was first demonstrated in 2009 with the development and real-time implementation of ADAPTS. Preliminary evaluations of ADAPTS have shown that the performance improvement with electronic adaptive scanning can be significant compared to conventional scanning strategies, especially when observing isolated storms (Heinselman and Torres 2011). ADAPTS works by turning “on” or “off” individual beam positions within a scanning strategy based on three criteria. If one or more