MPAR Software Upgrades Project
Focused observations provide a means to reduce update times with no sacrifice in data quality or spatial coverage by devoting less radar time to regions of reduced interest (e.g., clear air), thus reducing the total scan time. Scientists at the NSSL have been exploring the high-temporal resolution weather scanning capabilities of the agile-beam NWRT PAR for a number of years. Fast adaptive scanning with the NWRT PAR was first demonstrated with the development and real-time implementation of the Adaptive DSP Algorithm for Phased-Array Radar Timely Scans (ADAPTS). ADAPTS works by detecting regions with significant weather returns in real time; that is, it classifies individual beam positions within a scanning strategy as active or inactive based on two criteria: return significance and neighborhood.
Typically, in severe weather situations, meteorologists use radar to monitor and track the most intense storms. Traditional scanning strategies do not discriminate between regions of active and inactive weather, devoting equal attention to the two. ADAPTS has proven useful in reducing scan update times by focusing scanning in regions with active weather. However, in situations of widespread precipitation, ADAPTS does not differentiate between stratiform and convective regions. It is the convective regions that meteorologists are typically most interested in and identifying them is an important step in defining focused scanning strategies to reduce update times. A cluster identification algorithm has been implemented to identify these regions.
An important part of adaptive scheduling is the ability to track weather features. Since the NWRT PAR employs a single antenna, it is limited to scanning a 90-degree azimuthal sector at any given moment. In addition, the position of storms within the azimuthal sector changes in time. A weather tracking algorithm has been developed that tracks weather features and commands the antenna to a new position to keep features of interest inside the field of view.
Adaptive Storm Scheduling
The capability to schedule focused scans on specific storms and adaptively track them has been added to the NWRT PAR software. The scheduling algorithm utilizes the cluster identification and weather tracking algorithms to define a storm cell and its relative position with respect to the antenna field of view. As the storm moves, the scanning sector is updated. If necessary, the weather tracking algorithm commands the antenna to a new position to keep the storm inside the field of view.
Radial velocities are important in identifying and locating hazardous weather such as microbursts, strong winds, and tornadoes. In some instances, radial velocities cannot be determined due to contamination from distant storms. It is possible to reduce the contamination by adjusting the pulse repetition time (PRT) of the pulses used to calculate radial velocity. An algorithm has been developed that applies an optimal PRT for minimizing the contamination inside a sector. A manual adjustment is also supported through the user interface.