Tuesday, 11 January 2005
The North Alabama Lightning Mapping Array (LMA): A network overview
The North Alabama Lightning Mapping Array (LMA) is a 3-D VHF regional lightning detection system that provides on-orbit algorithm validation and instrument performance assessments for the NASA Lightning Imaging Sensor, as well as information on storm kinematics and updraft evolution that offers the potential to improve severe storm warning lead time by up to 50% and decrease the false alarm rate (for non-tornado producing storms). In support of this latter function, the LMA serves as a principal component of a severe weather test bed to infuse new science and technology into the short-term forecasting of severe and hazardous weather, principally within nearby National Weather Service forecast offices. The LMA, which became operational in November 2001, consists of ten VHF receivers deployed across northern Alabama and a base station located at the National Space Science and Technology Center (NSSTC), which is on the campus of the University of Alabama in Huntsville. The LMA system locates the sources of impulsive VHF radio signals from lightning by accurately measuring the time that the signals arrive at the different receiving stations. Each station records the magnitude and time of the peak lightning radiation signal in successive 80 ms intervals within a local unused television channel (channel 5, 76-82 MHz in our case). Typically hundreds of sources per flash can be reconstructed, which in turn produces accurate 3-dimensional lightning image maps (nominally <50 m error within 150 km range). The data are transmitted back to a base station using 2.4 GHz wireless Ethernet data links and directional parabolic grid antennas. There are four repeaters in the network topology and the links have an effective data throughput rate ranging from 600 kbits s -1 to 1.5 Mbits s -1. This presentation provides an overview of the North Alabama network, the data processing (both real-time and post processing) and network statistics.