Software Design for Coordinated Remote Control of Weather Radar Networks

The NSF Engineering Research for Collaborative Adaptive Sensing of the Atmosphere (CASA) pioneered the concept of dense networks of polarimetric X-band weather radars with its four radar Oklahoma network which it operated from 2006-2011. The concept continues in the Dallas Fort-Worth Metroplex where CASA and the North Central Texas Council of Governments operate a five (soon to be seven) radar research-to-operations (R20) testbed for weather warning systems (CASA WX). CASA WX operates as a living lab where CASA researchers, users, and stakeholders establish and evaluate research and R2O goals; and where the experimentation and demonstration takes place during real-time weather events. The end-to-end infrastructure includes heterogenous sensors from five different radar manufacturers that are networked together to create a wide range of integrated products that are disseminated to users through websites, mobile apps, and decision support tools, such as AWIPS2.

Deploying a network of X-band radars with overlapping coverage can provide significant advantages over single radars operating in isolation, such as low-level, integrated multi-Doppler data with very high spatial and temporal resolution. Operation as a network, however, required the creation of a software architecture that could not only coordinate the scans executed by the radars to obtain the high temporal update rates, but could also aggregate, process, and disseminate products derived from the high-bandwidth radar data in real-time. The CASA engineering research center has developed and operated such a software system for going on 10 years, first in its Oklahoma testbed and now in the CASA WX Dallas Fort Worth testbed. The system has proven to be robust, flexible, and extensible due to its asynchronous, distributed, modular structure. The asynchronous nature allows the system to continue operating despite sensor failure and communication interruptions and delays, as when a radar is knocked offline by a tornado or when an internet link to a radar experiences congestion. The modular structure makes the system extensible (virtually plug-and-play if CASA's interface specifications are followed) in that it is able to accept data from almost any radar platform, including X-bands from different manufacturers using different transmitter types, as well as NEXRAD and TDWR, which operate at different frequencies, resolutions, and temporal update rates. The modular structure also allows easy parallel operation of numerous data aggregators and product generators such as those for vector winds, quantitative precipitation estimation, hydrometer classification, and forecasting. Moreover, the distributed structure allows the various components that aggregate, process, and disseminate the data products to run not only on different computers in a central compute facility, but to run at remote locations where appropriate computing power is present, or to be run in the cloud using resources that are allocated dynamically as the weather situation, and hence the resulting computational and products needs, evolve from clear air to tracking a tornado.

This paper describes CASA's software system, highlighting those aspects that give the system its robustness and extensibility, and explaining the radar coordination approach (the so-called Meteorological Command and Control (MCC) module) that enables the current set of mechanically scanned radars to meet the needs of different users while at the same time achieving their signature high temporal update rates. The paper will also describe a demonstration whereby a small network of X-band phased-array radars of the kind being considered as a potential technology for the Next-Generation Surveillance and Weather Radar Capability (NSWRC) were integrated into the CASA WX testbed illustrating how the CASA software system provides a potential architecture for achieving the weather radar capability of this future multi-functional system.